Sites of behavioral and neurochemical action of ACTH-like peptides and neurohypophyseal hormones

Neuroscience & BiobehavioralReviews, Vol. 7, pp. 453-463, 1983. ©Ankho InternationalInc. Printed in the U.S.A.

Sites of Behavioral and Neurochemical Action of ACTH-like Peptides and Neurohypophyseal Hormones Tj. B. VAN W I M E R S M A G R E I D A N U S , B. B O H U S , 1 G. L. K O V A C S , z D. H . G. V E R S T E E G , J. P. H . B U R B A C H A N D D. D E W I E D

R u d o l f M a g n u s Institute for Pharmacology, Medical Faculty, State University o f Utrecht Vondellaan 6, 3521 GD Utrecht, The Netherlands R e c e i v e d 5 J a n u a r y 1983 WlMERSMA GREIDANUS, Tj. B. VAN,B. BOHUS, G. L. KOVACS, D. H. G. VERSTEEG, J. P. H. BURBACH AND D. DE WlED. Sites of behavioral and neurochemical action of ACTH-Iike peptides and neurohypophyseal hormones. NEUROSCI BIOBEHAV REV 7(4)453-463, 1983.--In order to localize the site of action of neuropeptides in relation to their effects on behavior and memory various approaches have been used. As a result of studies using rats bearing lesions in different areas of the limbic system as well as of studies in which neuropeptides were locally applied into various areas'of the brain it appeared that the limbic system (amygdala, hippocampus, septum and some thalamic areas) plays an essential role in the effect of vasopressin and ACTH and their derivatives on behavior and memory. Neurochemical studies generally indicate that changes occur in catecholamine utilization in these various limbic regions upon administration of these neuropeptides. It can be concluded that the effects of vasopressin in the terminal regions of the coeruleo-telencephalic noradrenalin system correlate with its effects on consolidation of memory. It is likely that the effects of vasopressin on other transmitter systems (e.g. dopamine in the amygdala and serotonin in the hippocampus) correspond with the effect of this neuropeptide on retrieval processes. In addition, regional differences in biotransformation of the neurohypophyseal hormones suggest that different patterns of behaviorally active fragments of these peptides may be present locally in the brain. Avoidance behavior

Limbic system structures

Neuropeptides

A variety of peptides has been shown to affect behavior by a direct action on the brain. Among the peptides which have been studied most extensively are pro-opiomelanocortin fragments (corticotropin (ACTH), a-melanocyte stimulating hormone (a-MSH), the endorphins) and the neurohypophyseal hormones vasopressin and oxytocin. The implication that ACTH and/or related peptides and the neurohypophyseal hormones affect brain functions related to behavior originated from the beneficial effects of these peptide hormones on the disturbed behavior of rats from which pituitaries had partially or totally been removed [9, 26, 27, 29, 30]. Similar effects were observed with fragments of these hormones such as ACTH-(I-10), ACTH-(410), and des-GlyNH2-[LysS]vasopressin (DG-LVP) [9, 29, 36], which are practically devoid of the classical endocrine effects in the periphery, e.g. on the adrenal cortex and on water homeostasis and blood pressure respectively. In intact rats A C T H and congeners profoundly affect the performance of behavioral responses, whether motivated by fear, hunger, thirst or sex [7]. These neuropeptides delay extinction of active avoidance behavior in a pole jump [28,91] or shuttle box avoidance situation [35], they facilitate passive avoidance behavior [25, 32, 40, 89], delay extinction

Neurotransmitters

of food motivated [43] or sexually motivated approach behavior [4], inhibit extinction of conditioned taste aversion [66], improve maze performance [69], facilitate reversal learning performance [70], alleviate experimental amnesia [67,68] etc. etc. It has been proposed that ACTH, MSH and related peptides enhance motivation, attention and/or vigilance and increase the arousal state of the brain in animal and man [32, 34, 64]. In general these effects are of a short term nature and last, depending on the dose used, from several hours to one day. With respect to the neurohypophyseal hormones, vasopressin stimulates acquisition of shuttle box avoidance behavior of hypophysectomized rats [9], increases resistance to extinction of active avoidance behavior [8, 31, 35, 94] and facilitates passive avoidance behavior [1, 8, 59, 87]. However, these effects are of long term nature and last far beyond the actual presence of the injected material in the organism. Vasopressin also prevents and reverses experimentally induced amnesia [14, 56, 63, 68]. In addition, T-maze choice reinforced by a sexual reward [4] and problem solving motivated by a food reward [5] are enhanced by vasopressin. Oxytocin generally has effects, which are opposite to those induced by vasopressin [46,71], although the effects of this

~Present address: Department of Behavioral and Neural Physiology, University of Groningen, Haren, The Netherlands. 2Permanent address: Institute of Pathophysiology, University Medical School, Szeged, Hungary.

453

VAN WIMERSMA GREII)AN[,IS I:I A I

454 peptide are easier demonstrable following intracerebroventricular (ICV) administration than after systemic injection [11,12]. From these data it was concluded that vasopressin improves memory functions in terms of an enhanced storage and retrieval of information, while oxytocin may be viewed as an amnesic peptide. The difference in behavioral effects of ACTH-related peptides on one hand and the neurohypophyseal hormones on the other hand may be caused by different sites of action in the brain and/or by different modes of action. For this reason attempts were made to determine the sites of action of these neuropeptides in the brain in relation to their behavioral effects. For this purpose various approaches can be used. Each of these approaches, however, has its own limitations and needs a specific interpretation. Lesion studies for instance may provide information on the sites of action of a systemically injected neuropeptide. It may be that the behavioral effect of a peripherally administered neuropeptide is blocked by a lesion in the brain, because the lesioned area represents the site of action. However, it might also be that the lesion only interrupts a circuit in the brain, which needs to be intact in order to permit the neuropeptide to display its behavioral effect and that the real site of action is remote from the lesioned area. Also local administration of small amounts of neuropeptides into restricted brain areas may not always prove that the actual site of behavioral action has been reached by the central injection site. Diffusion and/or spreading or even selective transport of the injected material may occur. The same holds for the local administration of specific antisera to various neuropeptides into restricted brain regions. Nevertheless, combination of the various techniques available may give a reliable answer to the question where the central sites of behavioral action of the neuropeptides a r e l o c a t e d . In order to localize the neurochemical events in the brain. which may underly the behavioral effects of the neuropeptides, the biotransformation of neuropeptides into smaller behaviorally active fragments was investigated in restricted brain areas. Furthermore, the utilization of brainmonoamines in anatomically distinct and restricted parts of the brain was studied after administration of various neuropeptides and after the bioinactivation of endogenous hormone in the brain by centrally applied antisera. The detailed results of the various studies on the sites of behavioral action of the respective neuropeptides have been published over the years in various journals. The aim of the present review is to re-evaluate the original data in an attempt to bring them together into a coherent picture on the mode(s) and site(s) of action and on brain mechanisms involved in the behavioral effects of neuropeptides. LESION STUDIES

Parafascicular Nuclei It appeared that bilateral lesions in the midposterior thalamic region which destroy the parafascicular nuclei completely block the inhibitory effect of during extinction systemically injected c~-MSH and ACTH-(4-10) on the extinction of a CAR in a shuttlebox or in a pole jumping avoidance situation [6,95]. F o r vasopressin the picture is different. Following systemic administration of [LysS]vasopressin (LVP) during extinction, rats bearing parafascicular lesions still display a delay of extinction of a CAR, although the effect is less pronounced than in sham-operated rats [95,97]. Thus, an intact parafascicular area is not essential for the effect of LVP,

because high amounts of LVP (5.4 p-g/ammal, subcutaneously (SC)) still inhibit extinction in rats with lesions in this region. A lower dose (1.8 p-g/animal SCt resulted only in a temporary improvement of avoidance perl\~rmance during extinction, while in sham-operated rats this dose induces a more permanent effect. Accordingly, animals with extensive lesions in the parafascicular area require more ~asopressin than intact animals to show long-lasting preservation of the pole-jumping avoidance response. This finding may suggest a decreased sensitivity of other areas in the brain tbr vasopressin and points to (an) additional brain structure,s) as (the) site(s) of behavioral action of vasopressin.

Septttm In order to localize these additional sites of behavioral action of vasopressin and ACTH-Iike peptides, rats with extensive bilateral lesions in the rostral septal area were used. This region was chosen because marked behavioral changes have been reported following lesions in or ablation of the septum [15,39]. The lesions performed by us destroyed the medial septal nuclei almost completely and damaged (part of) the hippocampo-cortical tract, the septal tract, the lateral septal nuclei and the nucleus accumbens. It appeared that doses of LVP up to 9 ~g systemically injected during extinction did not induce a preservation of the pole-jumping avoidance response in thus lesioned rats [971. The rostral septal area may also be a locus of behavioral action of ACTH or MSH or their fragments, since extensive lesions in this area completely block the inhibitory effect of ACTH-(4-10) on extinction of a CAR [89].

Hippocampus Small bilateral lesions in the antero-dorsal hippocampus causing a restricted damage to this area of the brain, partly inhibit the behavioral effect of LVP on the pole-jumping avoidance extinction, while extensive lesions in this structure completely prevent the inhibitory effects of vasopressin and of ACTH-(4-10) on extinction [92]. In these studies vasopressin was administered SC immediately after the last acquisition session of the CAR, whereas ACTH-(4-10) was injected one hour prior to each extinction session. In fact vasopressin as well as ACTH-(4-10) were completely ineffective on extinction of pole jumping avoidance behavior in doses up to 9/zg when rats with extensive lesions were used. In animals with smaller lesions only a dose of 9/zg of LVP induced a slight but significant delay in extinction, whereas a smaller dose (3 p,g) was ineffective [92].

Atnygdala Extensive bilateral lesions which destroy the central and basolateral parts of the amygdaloid complex also block the inhibitory action of vasopressin (DG-LVP) and of ACTH(4-10) on extinction of the pole-jumping avoidance response [99]. A single subcutaneous injection o f 3 /xg DG-LVP immediately after the last acquisition session induced a marked inhibition of extinction in sham-operated rats, whereas no effect of 5 p-g of this peptide could be observed in rats bearing amygdaloid lesions. Daily injections of 3 P-gACTH-(410) prior to each extinction session resulted in a inhibition of the CAR in sham-operated rats, whereas t r e a t m e n t with doses up to 9/xg of this neuropeptide was Completely ineffective in amygdatoid lesioned animals.

Fornfiv Transections From these data it has been suggested that vasopressin

SITES O F A C T I O N O F N E U R O P E P T I D E S and ACTH and their congeners do not act on a single anatomically well defined site of the brain but that they need an intact limbic system in order to display their behavioral effects. In order to test this hypothesis transections were made through the pre- and postcommissural fibers of the fornix, and the stria terminalis, immediately dorsal of the commissura anterior [100]. These cuts interrupt the main afferent and efferent connections of the hippocampus (fornix) and amygdala (stria terminalis). In fact fibers projecting to and/or from the septum, the pre-optic area, the corpora mammillaria and the amygdala are transected by this treatment. Interestingly, these transections do abolish the effect of ACTH-(4--10) (3 p.g or 9 g.g given during extinction) on extinction of the CAR completely, whereas the effect of the vasopressin analogue DG-LVP is still present when this lat: ter neuropeptide is given immediately after the last acquisition session [100]. However, if vasopressin is given during extinction its inhibitory action on extinction of the CAR has almost completely disappeared. Even taking into account differences in acquisition and/or extinction which occur due to the lesion itself, the differential effect of the fornix transection on the behavioral influence of ACTH-(4-10) and of DG-LVP is striking. Since ACTH-(4-10) acts on retrieval and not on storage of information, while vasopressin acts on both processes, the fornix transection discriminates most probably between processes related to storage and retrieval of information, and hence it seems likely that storage processes and retrieval processes are differentially localized. This idea is further supported by results from local injection of neuropeptides. The results of the lesion studies suggest that various regions of the brain being part of the limbic system (parafascicular area, dorsal hippocampus, amygdala, septum) are the anatomical substrate for the behavioral effect of neuropeptides (ACTH, vasopressin and their derivatives). However, whether these brain regions are as such the loci of action or whether more generally the timbic system needs to be intact in order to let these neuropeptides have their behavioral effects could not be assessed from these experiments. L O C A L ADMINISTRATION O F N E U R O P E P T I D E S A N D OF ANTIV A S O P R E S S I N SERUM A N D B E H A V I O R

Active Avoidance Behavior

As was mentioned extinction of a conditioned polejumping avoidance response is markedly affected by administration of ACTH, a - M S H and their fragments as well as by vasopressin. Therefore pole-jumping avoidance behavior was also used in an attempt to localize the site of this behavioral action of these neuropeptides upon central administration. Crystalline ACTH-(I-10) was applied randomly to different brain areas in rats equipped with a stainless steel plate with 12 holes and tubes which was fixed on the skull [91]. Intracerebral administration of the peptide was performed immediately after the first extinction session of the CAR and the effect of the treatment was studied in subsequent extinction sessions. Unilateral implantation of ACTH-(I-10) inhibited extinction of the pole-jumping avoidance response when the peptide was applied in the parafascicular nucleus, in the lateral habenular nucleus, in the tectospinal tract, in the cerebrospinal fluid (CSF) or in the liquor of the third ventricle. However, no effect of ACTH-(I-10) on extinction of the pole-jumping avoidance response was observed following unilateral implantation in the ventral thalamic nu-

455 cleus, the posterior thalamic nucleus, the nucleus reuniens, the fasciculus retroflexus, the globus pallidus, the caudate nucleus or the lateral preoptic nucleus. Similarly, 3 implantations in the tectospinal tract, and one implantation dorsocaudal to the parafascicular nucleus were ineffective [91]. Micro-injections of 0.1/xg of LVP, unilaterally applied in various brain areas, revealed that the brain sites in which injected LVP resulted in an inhibition of extinction of the pole-jumping avoidance response comprise the parafascicular nuclei, the parafascicular-posteromedial thalamic area, the posterolateral and ventromedial thalamic nuclei and the transition from the reticular formation into the parafascicular nuclei. Ineffective micro-injection sites were located in the ventromedial and anteromedial part of the thalamus, the posterior hypothalamus, the reticular formation, the substantia grisea and substantia nigra, the lateral lemniscus, the dentate gyrus, the putamen, the commissura fornicis, the corticohabenular tract or the cortex [94]. Generally, the results from the lesion studies together with those of the randomly applied neuropeptides in the brain suggest that at least one of the effective sites of action of ACTH-fragments and of vasopressin in terms of delaying the extinction of the pole-jumping avoidance response is located in the posterior thalamic region including the parafascicular nuclei. Passive Avoidance Behavior

Recent views on memory processes maintain that later retention of a learned behavioral response may be affected by interaction with either consolidation or retrieval processes [62]. Passive avoidance behavior is a useful paradigm to investigate the effects of substances on consolidation or retrieval. Generally a single learning trial is used followed by a retention session 24 hr later. Operationally, treatments given shortly after learning influence consolidation processes. Effects of treatments given shortly before a retention test are interpreted as influences on retrieval of memory. Reversal of experimentally induced amnesia by preretention treatment also suggests an action on memory retrieval. Behavioral observations using either peripheral [31] or intracerebroventricular [12] administration of vasopressin, or ICV injection of oxytocin [12] indicated that vasopressin and oxytocin affect both consolidation and retrieval of memory, but in an opposite manner (see also introduction). Observations in a one-trial learning passive (inhibitory) avoidance situation suggest that the effects of vasopressin on consolidation and retrieval processes are differentially localized in the limbic-midbrain system. In addition, the amnesic action of oxytocin is exerted generally through the same sites where vasopressin is active to facilitate memory. Micro-injection of 25 pg [ArgS]-vasopressin (AVP) into the dentate gyri of the hippocampus or of 50 pg into the dorsal raphe nucleus immediately after learning via permanently implanted cannules, facilitated later retention of the passive avoidance response. The same amounts of oxytocin injected into these structures exerted an amnesic effect. AVP and oxytocin were also effective when injected into the dorsal septal area. However, in contrast to other brain sites both peptides caused a facilitation of passive avoidance behavior (see Table l). Micro-injection of the peptides into the subiculum, central nuclei of the amygdala and locus coeruleus were ineffective [48,49]. It is not understood why vasopressin and oxytocin exert a similar effect when injected into the dorsal septal area. It may well be that the structural difference between the two peptides is not recognized by

VAN WIMERSMA GREII)ANUS E l Af,,

456

TABLE 1 EFFECTS OF LOCAL MICRO-INJECTION OF VASOPRESSIN, ANTIVASOPRESSIN SERUM AND OXYTOCIN ON MEMORY CONSOLIDATION, AMNESIA AND LOCAL CATECHOLAMINEUTILIZATION Dorsal septum

Dentate gyrus

Dorsal raphe

Central amygdala

+ n.d. n.d.

+ n.d. -

+ 0 -

0 n.d. n.d.

n.d. +

n.d. -

0 -

n.d, 0

0

+

0

+

NA

NA

NA

DA

+

0

+

Retention of passive avoidance behavior [Arg~]vasopressin 6OHDA + [ArgS]vasopressin antivasopressin serum 6OHDA + antivasopressin serum oxytocin Reversal of amnesia [ArgS]vasopressin Local catecholamine utilization [Arg~]vasopressin

-

For behavioral effects + and - denote a facilitatory and attenuating effect respectively; 0 denotes no effect. For local catecholamine utilization + and - denote an increased and decreased utilization respectively, while 0 denotes no effect. n.d.=not determined. Data from [13, 48, 49, 52, 54].

putative receptors. That the lateral-dorsal septum contains exclusively vasopressinergic nerve terminals [22] supports such a suggestion. In addition, intraseptal injections of either vasopressin or oxytocin increased peak theta frequency in the hippocampus during paradoxical sleep [80]. The effect of AVP on retrieval processes seems to be located in the dentate gyrus of the hippocampus and the central nuclei of the amygdala. This is suggested by observations showing that bilateral micro-injection of 100 rig AVP into these regions reverses pentylenetetrazol (PTZ) induced amnesia for a passive avoidance task, if given shortly before the retention test (see Table 1). Micro-injections of AVP into the dorsal septum and the median raphe nucleus appeared to be ineffective [13]. It should be mentioned, however, that micro-injections of AVP into the hippocampus and amygdaia led only to a partial reversal of PTZ-induced amnesia, while ICV administered AVP was able to reverse the behavior of the rats completely. It was suggested, therefore, that a concerted action of vasopressin on both areas is essential for a complete reversal of amnesia in the rat [13]. From these data it is concluded that the effects of vasopressin on storage processes and on retrieval are located in different brain areas. The dorsal septal area seems to be important for its effect on storage processes whereas the central nuclei of the amygdala are involved in its effect on retrieval. The dentate gyrus of the hippocampus seems to be the anatomical substrate for the effect of vasopressin on both storage and retrieval processes.

Local Application o f Antisera to Neuropeptides and Behavior In addition to the studies on the site(s) of behavioral ac-

tion of exogenous vasopressin, which was locally applied into various brain regions, studies were designed to determine the sites of action of endogenous vasopressin. Since extrahypothalamic pathways of vasopressin have been described [23, 55. 74], the physiological rote of endogenous vasopressin in limbic midbrain structures was explored. Specific antisera to this neuropeptide, which have been shown to induce marked behavioral changes upon ICV administration [93,96], were injected bilaterally into the dorsal hippocampus. It appeared that such a local intrahippocampal injection of anti-AVP serum also impairs passive avoidance retention [54]. An antiserum dilution of 1:50 results in a significantly impaired retention of the passive avoidance response when it is injected into the dorsal hippocampus immediately after the learning trial. This concentration of antiserum is not effective following ICV administration. Similar results were obtained when vasopressin-antiserum was microinjected into the dorsal raphe nucleus immediately after the learning trial [52]. Accordingly, those brain sites through which exogenous AVP was able to modulate memory consolidation seem to be involved in a physiological modulation of memory by the endogenous hormone. LOCAL EFFECTSOF NEUROPEPTIDESON BRAIN CATECHOLAMINES AS discussed in the foregoing paragraphs, (1) vasopressin exerts its effects on memory processes via particular timbic brain structures and (2) the brain contains an extensive network of vasopressin-containing neurons projecting to various brain regions and most prominently to limb/c structures [23,74]. Since submaximal doses of the tyrosine hydroxylase inhibitor t~-methyl-p-tyrosine (c~-MPT) prevented a behav-

SITES O F ACTION O F N E U R O P E P T I D E S

457

B

A BRAIN REGION

NORADRENALINE UTILIZATION (% of controls) decrease -50 I

DOPAMINE UTILIZATION (% of controls)

BRAIN REGION

decrease

increase +50

0 i

I

increase

-50

!

0

I

I

|

+50 I

It

dorsal septal nucl. caudate nucl.

supraoptic nucl.

-[

.mi

arcuate nucl. arcuate nucl.

]

parafasc, nucl.

--]m

__]o

median eminence

dorsal raphe nucl. !dorsal raphe nucl.

-"'-'7t~ E] AVP

locus coeruleus

II

--1

(i.c.v.) vs. saline

tm HO-DI vs. controls t~1 anti-AVP

serum (i.c.v.) vs. control

serum

n.t.s

AI-region

"'"10

FIG. 1. Catecholamine utilization in microdissected brain nuclei following ICV injection of [Ar#]vasopressin and antivasopressin serum and in the homozygous Brattleboro rat with hereditary diabetes insipidus (HO-DI). (A) Noradrenaline utilization; (B) dopamine utilization. Data from [76, 83, 84].

ioral action of AVP [45], vasopressin might exert its effects in concert with or via brain catecholamines. It is also well established that the brain monoamines noradrenaline, dopamine and serotonin are involved in learning, memory consolidation and retrieval processes and evidence in favor of a role of noradrenaline is particularly abundant (for references see [13, 24, 44, 47, 50, 60, 61]). F o r the evaluation of the role of noradrenaline in the effects of vasopressin on behavior three approaches have been fruitful: (1) the study of the effects of vasopressin on catecholamine transmission by using drugs which alter the availability of central catecholamines (2) the study of the effects of vasopressin on consolidation and retrieval processes following selective lesioning of monoamine systems in the brain and (3) the study concerning the correlation of regional noradrenaline metabolism in the brain with the performance of rats in avoidance paradigms. Results of such studies support the notion that the activity of specific catecholamine pathways, rather than the general activity of catecholamine systems in the brain contributes to the processing of information related to memory consolidation [47, 50, 53]. Administration o f Vasopressin A first approach has been the measurement of the effect of vasopressin on brain catecholamine synthesis or turnover. Whereas no effects were found of LVP or A V P on the in vivo

conversion of [aH]tyrosine into tritiated catecholamines in whole brain of mice [38,42] or rats (Versteeg and Wurtman, unpublished observations), it appeared that these peptides. administered either systemically (LVP, [45]) or intracerebroventricularly (ICV) (AVP, [77]) did affect catecholamine metabolism selectively in a number of restricted brain regions. Thus, vasopressin was found to cause an enhancement of the utilization of noradrenaline in the hypothalamus, thalamus and medulla oblongata, but not in septum, preoptic area, hippocampus and amygdala [45,77]. Similarly, vasopressin enhanced the utilization of dopamine in the preoptic area, septum and striatum, but not in hypothalamus and amygdala [45,77]. In addition to this, the dopamine concentration of the hypothalamus, septum and striatum were found to be decreased following LVP administration [45]. These results pointed to the involvement of distinct catecholamine systems. Tanaka et al. [76] therefore subsequently studied the effect of ICV administered AVP in a dose of 30 ng per rat, on aMPF-induced catecholamine disappearance in specific brain nuclei. The nuclei were selected on the basis of several critria, among which the most important were (a) their location within structures implicated as being involved in the effects of vasopressin and fragments on behavior, e.g. rostral septal area, parafascicular region of the thalamus and dorsal hippocampus [92, 95, 97] and (b) the afferent input from the extrahypothalamic vasopressin system [23,74]. It was found that following vasopressin treatment noradrenaline utilization was

458 enhanced in a number of nuclei among which were the dorsal septal nucleus, the anterior hypothalamic nucleus, the parafascicular nucleus, the dorsal raphe nucleus, the locus coeruleus, while dopamine utilization was enhanced in, among others, the caudate nucleus, the median eminence, and the dorsal raphe nucleus; noradrenaline utilization was reduced in the supraoptic nucleus and the nucleus ruber [76] (see Fig. IA,B). In 35 other nuclei no effects were seen. These results were interpreted as indicating that vasopressin might be a modulator of the activity of (parts of) particular catecholamine systems in the brain [45, 76, 77]. Brattleboro R a t s and Administration o f Antisera to Vasopressin

To test the possibility whether endogenous vasopressin also affects catecholamine turnover two situations were studied in which the bioavailability of endogenous vasopressin in the brain is absent or low. Whereas vasopressin administration inhibits the extinction of active avoidance behavior and facilitates the retention of a passive avoidance response, homozygous diabetes insipidus rats of the Brattleboro strain, which lack the capacity to synthesize vasopressin display a disturbed maintenance of a learned response [3, 10, 37, 90]. In addition, Wistar rats treated ICV with antivasopressin serum display memory deficits as indicated by facilitated extinction of an active avoidance response, and attenuation of passive avoidance behavior [93, 96, 98]. In a study in which catecholamine utilization in microdissected nuclei from the brains of homozygous Brattleboro rats was compared with that of homozygous non-diabetic controls [83] it was found that, in general, regional catecholamine turnover was changed in a direction opposite to that of the changes observed following ICV vasopressin administration [76] (see Fig. 1A,B). Interestingly, it appeared that not only the turnover of noradrenaline and dopamine was decreased in particular nuclei, but also that of adrenaline in the periventricular and paraventricular nuclei and in the A2region of the medulla oblongata. Similar results were reported for noradrenaline and dopamine turnover and 5-HT levels in large brain parts [51]. A decreased turnover of noradrenaline in the hypothalamus and of dopamine in striatum of homozygous Brattleboro rats as compared to that of heterozygous non-diabetic rats and an increased noradrenaline turnover in the septum were found, which for the former two regions is opposite to the effects found in LVP treated rats [45] (see Fig. IA). Since it is conceivable that the altered catecholamine turnover in the brain of Brattleboro rats could also be due to disorders not related to the absence of vasopressin, a second model with a reduced amount of bio-available vasopressin was studied, viz. the Wistar rat treated ICV with antivasopressin serum. Though the effects were less pronounced than in Brattleboro rats, it was found that following ICV injection of anti-vasopressin serum catecholamine utilization was decreased in those regions in which vasopressin treatment had been found to cause an enhanced utilization [84]. Taken together, these neurochemical data suppo~ the hypothesis that endogenous vasopressin present in the brain modulated the activity of distinct catecholamine-containing neurons: in general increased amounts of vasopressin in the brain lead to an enhanced activity, whereas a decreased bio-availability of this neuropeptide results in a diminished activity of these catecholamine neurons. Less is known about the interaction of vasopressin with

VAN W I M E R S M A G R E I I ) A N [ ! S I'1 AL. brain serotonin, though there is evidence that ~asopressin also acts as a modulator of the activity of specific serotonin systems in the brain [2, 51.65, 78, 79]. Administration ~[' Oxytocin or A ( T t t

Comparable sets of data as for vasopressin are as yet not available for oxytocin and the ACTH-Iike peptides. Telegdy and Kovfi,cs [78,79] have carried out experiments in which catecholamine concentrations and turnover was measured in four brain regions of oxytocin-treated rats in a design identical to that for vasopressin [45]. These authors observed a decreased noradrenaline concentration in hypothalamus, striatum and septum 10 min after oxytocin administration, and a reduced turnover of noradrenaline and dopamine in the striatum and an increased turnover of dopamine in the hypothalamus. Results of preliminary experiments by Van HeuvenNolsen and Versteeg (unpublished observations) with microdissected brain nuclei show regional effects after ICV oxytocin administration which in several regions are opposite to those found after vasopressin. Though initially, on basis of data concerning brain noradrenaline turnover in hypophysectomized and adrenalectomized rats, Weiss et al. [88] and H6kfelt and Fuxe [41] hypothesized that a correlation may exist between the rate of extinction of conditioned avoidance behavior and central noradrenaline turnover. Subsequent results of experiments relating effects of ACTH fragments on this parameter with those on behavior proved to be conflicting and not in support of such a hypothesis [38, 42, 57, 81, 82]. LOCAL INVOLVEMENT OF BRAIN NEUROTRANSM1SSION IN THE EFFECTS OF VASOPRESSINON PASSlVE AVOIDANCEBEHAVIOR Brain monoamines play an important role in brain processes as learning and memory [13, 24, 44, 47, 50, 60, 61], The action of vasopressin on memory processes and on alterations in noradrenergic function as found following ICV administration of this neuropeptide seems to occur in more or less similar brain regions. It was therefore a logical step to investigate next whether interaction of AVP with the noradrenergic transmission is of importance for the action of this peptide on memory processes. Kov~ics et al. [45] studied the effect of LVP on passive avoidance behavior and they found that a partial blockade of catecholamine synthesis by a low dose of cz-MPT both during learning and retention interferes with the influence of the peptide on this behavior. In combination with behavioral studies the influence of AVP on the a-MPT-induced disappearance in individual brain nuclei following peptide micro-injection into the dentate gyri of the hippocampus, the dorsal septum, and the dorsal raphe nucleus was investigated [49]. It appeared that the peptide induced local changes in the case of dentate gyrus and the dorsal septum. Noradrenaline disappearance rate was accelerated in the hippocampus and decreased in the septum. Although no local changes did occur following AVP microinjection into the dorsal raphe nucleus, dopamine disappearance rate was accelerated in the locus coeruleus (see Table 1). These observations favoured the notion that the peptide is probably acting via terminals of the noradrenergic neurons rather than at the level of the cell bodies. The sites where vasopressin affected memory processes were those where the fibers of the dorsal noradrenergic bundle system (DNB) arising from the A~; noradrenergic cell bodies in the locus coeruleus terminate [58]. The involvement of the DNB in

SITES OF ACTION OF N E U R O P E P T I D E S learning and memory processes has been repeatedly emphasized [24,44]. Observations in rats with selective chemical lesions in the DNB with 6-hydroxydopamine (6-OHDA) led to the conclusion that modulation of noradrenergic transmission by AVP, most probably at the level of the presynaptic terminals of the DNB, is of primary importance in the action of the peptide on memory consolidation [48,49]. Facilitation of memory consolidation by AVP was fully absent in rats with 6-OHDA lesions in the DNB. This type of lesion however did not prevent completely the action of AVP on the retrieval of memory, suggesting that the DNB is rather selectively involved in mediating the influence of AVP on consolidation processes. That endogenous vasopressin also affects the activity of catecholaminergic terminals in particular brain regions was shown by studies in which antivasopressin serum was injected into the dorsal raphe nucleus [52]. A postlearning injection of the antiserum resulted in impaired avoidance retention. This effect was absent if catecholamine nerve endings, which impinge on 5-HT cell bodies, were destroyed by 6-OHDA (see Table 1). Although the influence of systemically administered AVP on memory consolidation was not abolished by destruction of the ascending 5-HT system [50], serotonergic innervation of the brain seems to be affected by vasopressin and to have a role in CNS effects of the peptide. Accordingly, intraventricular injection of LVP affected the steady state level of 5-HT in various brain regions [73] and 5-HT levels of Brattleboro homozygous rats were also different from the heterozygous littermates [51]. It appears that although the ascending 5-HT system plays a secondary (secondary to NE) role in the effect of AVP on memory consolidation [50], the effect of AVP on retrieval processes requires an intact ascending 5-HT system. Chemical lesion by 5,6-DHT in the raphe nucleus prevented the effect of pretest administration of AVP [13]. These observations indicate that the action of AVP on consolidation and retrieval of memory involves a selective interaction with distinct monoaminergic systems in the brain. L O C A L B I O T R A N S F O R M A T I O N OF N E U R O P E P T I D E S IN T H E BRAIN

A general feature of neuropeptides is that their biosynthesis, biotransformation, and inactivation involve the action of proteolytic enzymes. On one hand, functional proteolytic events have been defined in the processing of high molecular weight precursor proteins [75]. This process takes place intracellularly in the neuropeptide producing cell. On the other hand, proteolytic enzymes associated with the target cell of the neuropeptides are thought to be responsible for the termination of neuropeptide action [72]. In addition to these two proteolytic functions it has recently been emphasized that proteolytic enzymes are involved in the biotransformation of neuropeptides into smaller peptides, with distinct central activity. This type of proteolysis may be associated with the synthesizing cells or could act on neuropeptides once they are secreted from their synthesizing cells and hence may be indicated as "postsecretional processing" [18]. This would allow these proteolytic enzymes to regulate neuropeptide activity and to control the population of behaviorally active neuropeptides. The conceptual basis of functional neuropeptide biotransformation has been provided by studies on the behavioral effects of neuropeptides and their fragments. In particular it has been recognized that the central effects of peptides such as vasopressin, oxytocin, ACTH, and/3-endorphin are

459 not limited to the entire peptide structure [33,34]. Several fragments of these peptides elicit strong central effects which are often distinctly different from those of the parent peptides. Based on these studies we have set out to investigate the proteolytic conversion of neuropeptides by brain synaptic membranes prepared from specific brain regions. These membranes may represent the cellular structures to which neuropeptides become available after extrusion from their synthesizing cells. The main mechanisms by which proteolytic enzymes in synaptic membranes convert the neurohypophyseal hormones and/~-endorphin has been delineated [17, 18, 19, 21] and studies on local biotransformation of oxytocin have been performed [20]. Two routes in the conversion of neurohypophyseal hormones have been identified. An enzyme activity cleaves initially the CysI-Tyr2 bond of arginine-vasopressin and oxytocin, without prior reduction of the disulfide bridge in the peptides, and proceeds by sequential removal of the NH2terminal amino acids Tyr 2, Phe 3 or Ile 3 etc. [20]. Structural characteristics of the peptide fragments which are formed by this mechanism are the intact COOH-terminal portion, the conserved Cys~-S-S-Cys6 bridge, and the remaining residues of the ring portion of the intact neurohypophyseal hormones [19]. Based on structure-activity studies with synthetic neurohypophyseal hormone fragments, which have been derived from the ring or the acyclic portions of the molecules, and on the importance of various amino-acid residues for biological activity [85,86] it was anticipated that central activities reside in some proteolytically generated fragments. Indeed, preliminary experiments have revealed that some metabolites of vasopressin and oxytocin are exceedingly more potent and selective in affecting passive avoidance behavior than the parent peptides. In particular, the COOH terminal hexapeptide fragment of argininevasopressin pGlu-Asn-Cys(Cys)-Pro-Leu-Gly-NH2, was 1000 times more potent than arginine-vasopressin in facilitating memory consolidation [ 16]. These observations point to a functional role of neuropeptide biotransformation. A minor route of neurohypophyseal hormone conversion involved cleavages in the COOH-terminal portion of the molecules. These cleavages generate the COOH-terminal dipeptides together with the sequence 1-7 of arginine-vasopressin and oxytocin or the des-glycinamide fragments [20]. Behavioral effects of these fragments have been found following intracerebroventricular administration [53]. Since local differences in neuropeptide blotransformation may yield a different set of neuroactive fragments, we have investigated the local biotransformation of neurohypophyseal hormones in brain. Employing oxytocin preparations which were differentially 14C-labelled in residue Tyr 2 and GlyNH2 "~, both the aminopeptidase activity and the enzyme activities acting on the COOH-terminal portion have been determined in a membrane fraction of restricted brain areas implicated in behavioral effects of the neurohypophyseal peptides and their fragments [19,20]. Lowest aminopeptidase activity was found in the parietal cortex, which was used as a reference region. Highest activity was present in membranes from the medial basal hypothalamus, nigro-striatal area and the dorsal raphe. Brain areas which contained intermediate activity were the dorsal septum, amygdala, gyrus dentatus, and the region containing preoptic area and anterior hypothalamus. The accumulation of an amino-peptidase split product showed a regional distribution parallel to that of the aminopeptidase activity.

460

VAN W I M E R S M A GREII)ANt+S E l A I .

COOH-terminal cleavages, as measured by the release of COOH-terminal glycinamide were lowest in cortex, dorsal septum, amygdala and gyrus dentatus. Preoptic area and anterior hypothalamus, nigrostriatum and dorsal raphe possessed higher activity, while the glycinamide releasing activity in membranes of the medial basal hypothalamus was markedly elevated. It is tempting to speculate that oxytocin converting activities are associated with neurohypophyseal hormone containing neuron systems. However, proteolytic activities were also detected in parietal cortex, an area which contains only very low amounts of vasopressinergic fibers, although the activity of enzymes was the lowest of those of tested regions. The regional differences in oxytocin converting peptidases may reflect local differences in metabolism of the neurohypophyseal peptides, which could result in a different pattern of metabolites. Although it is tempting to assume that such regional differences in biotransformation may underly the differential effects of oxytocin and vasopressin in various brain regions [13, 48, 49, 50], as yet our knowledge on neurohypophyseal converting peptidases is too limited to allow us to correlate the local differences in peptidase activity with the differential behavioral effects of locally administered oxytocin and vasopressin. DISCUSSION AND CONCLUSION The present review deals with the brain sites of action of A C T H and neurohypophyseal hormones in relation to their behavioral effects. The first experiments performed on this subject dealt with the behavioral effect of randomly applied ACTH-(1-10) and vasopressin in the rat brain [91,94] and with the effects of a - M S H and vasopressin in rats bearing lesions in the parafascicular area [6,95]. Since the local implantations of this neuropeptide were unilaterally applied and the lesioned area does not necessarily represent the single anatomical substrate for the behavioral effect of the neuropeptides used, it was thought that the parafascicular nuclei played an important role in their behavioral effects. However, it could not be concluded that the parafascicular area is the site of action of these neuropeptides. It might be that this region is just needed for the expression of their effect on behavior. More extensive studies using rats with lesions in various limbic midbrain regions, as well as experiments in which small amounts of neuropeptides (in particular vasopressin and oxytocin) were bilaterally applied into restricted brain areas, pointed to additional structures (sep-

tum, dorsal hippocampat complex, dorsal raphe al-ea+ amygdala) involved in the behavioral e f f e c t s o f ACTH-like peptides and vasopressin. Vasopressin appeared to affect storage as well as retriewd processes. Since the multiple learning trial paradigms as used in active avoidance conditioning do not seem the most appropriate situations to differentiate between these two processes underlying the behavioral effect of this neuropeptide, passive avoidance behavior was also used to determine the sites of behavioral action of vasopressin. These studies revealed that the effect of vasopressin on retrieval processes seems to be located in the central nuclei of the amygdala, whereas the dorsal septal and the dorsal raphe areas are involved in the influence of vasopressin on storage processes. The dentate gyrus of the hippocampus seems to be the anatomical substrate for the effect of vasopressin on both storage and retrieval processes. Studies on the local changes in turnover of brain catecholamines and other neurotransmitters in restricted brain regions revealed that in addition to different brain sites also different neurotransmitters may be involved in the behavioral actions of neuropeptides, depending whether mainly storage processes or retrieval processes are affected. This makes an explanation on the various behavioral effects of ACTH-Iike peptides and of neurohypophyseal hormones rather complicated. It is postulated that if the behavioral effect of neuropeptide treatment is a result of changes in retrieval p r o c e s s e s - in which attention, specific arousal and/or vigilance are involved--the main site of action is located in the amygdala and the dentate gyrus of the hippocampal complex with dopamine and serotonin as the respective neurotransmitter systems involved. In case the behavioral effect of the neuropeptides is apparently due to changes in storage processes--generally indicated as consolidation--the main sites and mechanism of action include the noradrenaline terminals in the dorsal septurn, dorsal raphe and dentate gyrus of the dorsal hippocampus. Moreover the differential effects of oxytocin in different brain sites may be explained by receptor specificity. In the septum receptors may recognize vasopressin and oxytocinlike molecules equally well, while receptors in the gyrus dentatus of the hippocampus may discriminate between these peptides. An additional factor influencing the local effects of neurohypophyseal hormones might be the metabolic conversion into behaviorally active fragments.

REFERENCES I. Ader, R. and D. De Wied. Effects of lysine vasopressin on passive avoidance learning. Psychon Sci 29: 46-48, 1972. 2. Auerbach, S. and P. Lipton. Vasopressin augments depolarization-induced release and synthesis of serotonin in hippocampal slices. J Neurosci 2: 477--482, 1982. 3. Bailey, W. H. and J. M. Weiss. Evaluation of a "memory deficit" in vasopressin-deficient rats. Brain Res 162: 174-178, 1979. 4. Bohus, B. Effects of desglycinamide-lysine vasopressin (DGLVP) on sexually motivated T-maze behavior of the male rat. Horrn Behav 8" 52--61, 1977. 5. Bohus, B. Neuropeptide und C_.~d/ichtnis. In: Hirnorganische Psychosyndrome im Alter, edited by D. Bente, H. Coper and S. Kanowski. Berlin: Springer-Verlag, 1982.

6. Bohus, B. and D. De Wied. Failure of c~-MSH to delay extinction of conditioned avoidance behavior in rats with lesions in the parafascicular nuclei of the thalamus. Physiot Behav 2: 221-223, 1967. 7. Bohus, B. and D. De Wied. Pituitary-adrenal system hormones and adaptive behaviour. In: General. Comparative and Clinical Endocrinology o f the Adrenal Cortex. edited by I. C. Jones and I. W. Henderson. London: Academic Press. 1980. 8. Bohus, B., R. Ader and D. De Wied. Effects of vasopressin on active and passive avoidance behavior. Horm Behav 3: 191197, 1972. 9. Bohus, B., W. H. Gispen and D. De Wied. Effect of lysine vasopressin and ACTH 4.-10 on conditioned avoidance behavior of hypophysectomized rats. Neuroendocrinology 11: 137143. 1973.

SITES OF ACTION OF NEUROPEPTIDES

10. Bohus, B., Tj. B. van Wimersma Greidanus and D. De Wied. Behavioral and endocrine responses of rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain). Physiol Behav 14: 60%615, 1975. 11. Bohus, B., I. Urban, Tj. B. van Wimersma Greidanus and D. De Wied. Opposite effects of oxytocin and vasopressin on avoidance behavior and hippocampal theta rhythm in the rat. Neuropharmacology 17: 23%247, 1978. 12. Bohus, B., G. L. Kov~tcs and D. De Wied. Oxytocin, vasopressin and memory: opposite effects on consolidation and retrieval processes. Brain Res 157: 414--417, 1978. 13. Bohus, B., L. Conti, G, L. Kov~ics and D. H. G. Versteeg. Modulation of memory processes by neuropeptides: Interaction with neurotransmitter systems. In: Neuronal Plasticity and Memory Formation. edited by C. A. Marsan and H. Matthies. New York: Raven Press, 1982. 14. Bookin, H. B. and W. D. Pfeifer. Effect of lysine vasopressin on pentylenetetrazol-induced retrograde amnesia in rats. Pharmacol Biochem Behav 7: 51-54, 1977. 15. Brady, J. V. and W. J. H. Nauta. Subcortical mechanisms in emotional behavior: Affective changes following septal forebrain lesions in the albino rat. J Comp Physiol Psyehol 46: 33%346, 1953. 16. Burbach, J. P. H., G. L. Kov/tcs, D. De Wied, J. W. van Nispen and H. M. Greven. A major metabolite of argininevasopressin in brain is a highly potent neuropeptide. Science, in press, 1983. 17. Burbach, J. P. H. and D. De Wied. Proteolytic conversion of /3-endorphin into behaviourally active peptides. In: Neuronal Plasticity and Memory Formation, edited by C. Ajmone Marsan and H. Matthies. New York: Raven Press, 1982. 18. Burbach, J. P. H. and E. R. de Kloet. Proteolysis of /3-endorphin in brain tissue. Peptides 3: 451-453, 1982. 19. Burbach, J. P. H. and J. L. M. Lebouille. Proteolytic conversion of arginine-vasopressin and oxytocin by brain synaptic membranes. Characterization of formed peptides and mechanism of proteolysis. J Biol Chem 258: 1487-1494, 1983. 20. Burbach, J. P. H., E. R. de Kloet and D. De Wied. Oxytocin biotransformation in the rat limbic brain: characterization of peptidase activities and significance in the formation of oxytocin fragments. Brain Res 202: 401-414, 1980. 21. Burbach, J. P. H., E. R. de Kloet, P. Schotman and D. De Wied. Proteolytic conversion of/3-endorphin by brain synaptic membranes: Characterization of generated /3-endorphin fragments and proposed metabolic pathway. J Biol Chem 256: 12463-12469, 1981. 22. Buijs, R. M. and D. F. Swaab. Immuno-electron microscopical demonstration of vasopressin and oxytocin synapses in the limbic system of the rat. Cell Tissue Res 2114: 355-365, 1979. 23. Buijs, R. M., D. N. Velis and D. F. Swaab. Extrahypothalamic vasopressin and oxytocin innervation of fetal and adult rat brain. Prog Brain Res 53: 15%167, 1980. 24. Crow, T. J. Cortical synapses and reinforcement: A hypothesis. Nature 219: 736-737, 1968. 25. Dempsey, G. L., A. J. Kastin and A. V. SchaUy. The effects of MSH on a restricted passive avoidance. Horm Behav 3: 333337, 1972. 26. De Wied, D. Influence of anterior pituitary on avoidance learning and escape behavior. Am J Physiol 207: 255-259, 1964. 27. De Wied, D. The influence of the posterior and intermediate lobe of the pituitary and pituitary peptides on the maintenance of a conditioned avoidance response in rats. lnt J Neuropharmacol 4: 157-167, 1965. 28. De Wied, D. Inhibitory effect of ACTH and related peptides on extinction of conditioned avoidance behavior in rats. Proc Soc Exp Biol Med 122: 28-32, 1966. 29. De Wied, D. Effects of peptide hormones on behavior. In: Frontiers in Neuroendocrinology, edited by W. F. Ganong and L. Martini. London: Oxford University Press, 1969. 30. De Wied, D. The anterior pituitary and conditioned avoidance behaviour. Excerpta Medica Int. Congress Series no. 184, 310-316, 1969.

461

31. De Wied, D. Long-term effect of vasopressin on the maintenance of a conditioned avoidance response in rats. Nature 232: 58-60, 1971. 32. De Wied, D. Pituitary-adrenal system hormones and behavior. In: The Neurosciences, edited by F. O. Schmitt and F. G. Worden. Cambridge: MIT Press, 1974. 33. De Wied, D. Behavioral effects of I.C.V. administrated vasopressin and vasopressin fragments. Life Sci 19: 685-690, 1976. 34. De Wied, D. Behavioral effects of neuropeptides related to ACTH, MSH, and /3-LPH. Ann N Y Acad Sci 297: 263-274, 1977. 35. De Wied, D. and B. Bohus. Long term and short term effects on retention of a conditioned avoidance response in rats by treatment with long acting pitressin and tx-MSH. Nature 212: 1484-1486, 1966. 36. De Wied, D., H. M. Greven, S. Lande and A. Witter. Dissociation of the behavioral and endocrine effects of lysine vasopressin by tryptic digestion. B r J Pharmaco145:118-122, 1972. 37. De Wied, D., B. Bohus and Tj. B. van Wimersma Greidanus. Memory deficit in rats with hereditary diabetes insipidus. Brain Res 85: 152-156, 1975. 38. Dunn, A. J., P. M. Iuvone and H. D. Rees. Neurochemical responses of mice to ACTH and lysine vasopressin. Pharmacol Biochem Behav 5: 139-145, 1976. 39. Fried, P. A. The septum and behavior: A review. Psychol Bull 78: 292-310, 1972. 40. Greven, H. M. and D. De Wied. The influence of peptides derived from corticotrophin (ACTH) on performance. Structure activity studies. Prog Brain Res 39: 429-442, 1973. 41. H6kfelt, T. and K. Fuxe. On the morphology and the neuroendocrine role of the hypothalamic catecholamine neurons. In: Brain-Endocrine Interaction, Median Eminence: Structure and Function, edited by K. M. Knigge, D. E. Scott and A. Weindl. Basel: Karger, 1972. 42. Iuvone, P. M., J. Orasco, R. L. Delanoy and A. J. Dunn. Peptides and the conversion of [3H]tyrosine to catecholamines: Effects of ACTH analogs, melanocyte-stimulating hormones and lysine vasopressin. Brain Res 139: 131-139, 1978. 43. Kastin, A. J., G. L. Dempsey, B. LeBlanc, K. Dyster-Aas and A. V. Schally. Extinction of an appetitive operant response after administration of MSH. Horm Behav 5: 135-139, 1974. 44. Kety, S. S. The biogenic amines in the central nervous system: Their possible role in arousal, emotion and learning, In: The Neurosciences, edited by F. O. Schmitt. New York: Rockefeller University Press, 1970. 45. Kov~ics, G. L., L. V6csei, G. Szab6 and G. Telegdy. The involvement of catecholaminergic mechanisms in the behavioural action of vasopressin. Neurosci Lett 5: 337-344, 1977. 46. Kovacs, G. L., L. V6csei and G. Telegdy. Opposite action of oxytocin to vasopressin in passive avoidance behavior in rats. Physiol Behav 20: 801-802, 1978. 47. Kov~ics, G. L., B. Bohus and D. H. G. Versteeg. Role of noradrenergic neurotransmission in the coeruleo-telencephalic projection in the effects of vasopressin on memory processes. Neuroscience 4" 152%1537, 1979. 48. Kov~ics, G. L., B. Bohus and D. H. G. Versteeg, Facilitation of memory consolidation by vasopressin: mediation by terminals of the dorsal noradrenergic bundle ? Brain Res 172: 73-85, 1979. 49. Kowics, G. L., B. Bohus, D. H. G. Versteeg, E. R. de Kloet and D. De Wied. Effect of oxytocin and vasopressin on memory consolidation: sites of action and catecholaminergic correlates after local microinjection into limbic-midbrain structures. Brain Res 175: 303-314, 1979. 50. KovCtcs, G. L., B. Bohus and D. H. G. Versteeg. The interaction of posterior pituitary neuropeptides with monoaminergic neurotransmission: Significance in learning and memory processes. Prog Brain Res 53: 123-140, 1980. 51. Kov~ics, G. L., G. Szab6, L. Szont~igh, I. Medve, G. Telegdy and F. A. L~iszl6. Hereditary diabetes insipidus in rats. Altered cerebral indolamine and catecholamine metabolism. Neuroendoerinology 31: 189-193, 1980.

462 52. Kov~ics, G. L., L. V6csei, L. Medve and G. Telegdy. Effect on memory processes of anti-vasopressin serum microinjected into the dorsal raphe nucleus: the role of catecholaminergic neurotransmission. Exp Brain Res 38: 357-361, 1980. 53. Kowics, G. L., B. Bohus, D. H. G. Versteeg, G. Telegdy and D. De Wied. Neurohypophyseal hormones and memory. In: Advances in Pharmacology and Therapeutics 11, vol. I. CNS Pharmacology, Neuropeptides, edited by H. Yoshida, Y. Hagihara and S. Ebashi. Oxford/New York: Pergamon Press. 1982. 54. Kov~ics, G. L., R. M. Buijs, B. Bohus and Tj. B. van Wimersma Greidanus. Microinjection of arginine~-vasopressin antiserum into the dorsal hippocampus attenuates passive avoidance behavior in rats. Physiol Behav 28: 45-48, 1982. 55. Kozlowski, G. P., G. Nilaver and E. A, Zimmerman. Distribution of neurohypophysial hormones in the brain. Pharmacol Ther, in press, 1982. 56. Lande, S., J. B. Flexner and B. Flexner. Effect of corticotropin and desglycinamideMysine vasopressin on suppression of memory by puromycin. Proc Natl Acad Sei USA 69: 558-560, 1972. 57. Leonard, B. E. The effects of two synthetic ACTH analogues on the metabolism of biogenic amines in the rat brain. Arch lnt Pharmacodyn Ther 207: 242-253, 1974. 58. Lindvall, O. and A. Bj6rklund. The organization of the ascending catecholamine neuron systems in the rat brain as revealed by the glyoxylic acid fluorescence method. Aeta Physiol Stand suppl. 412, 1-48. 59. Lissfi.k, K. and B. Bohus. Pituitary hormones and avoidance behavior of the rat. lnt J Physiobiol 2:103-115, 1972. 60. Mason, S. T. and S. D. Iversen. Behavioral basis of the dorsal bundle extinction effect. Pharmacol Biochern Behav 7: 373379, 1977. 61. Mason, S. T. and H. C. Fibiger. Evidence for a role of brain noradrenaline in attention and stimulus sampling. Brain Res 159: 421-426, 1978. 62. McGaugh, J. L. Time dependent processes in memory storage. Science 153: 1351-1358, 1966. 63. Pfeifer, W. D. and H. B. Bookin. Vasopressin antagonizes retrograde amnesia in rats following electroconvulsive shock. Pharmacol Biochem Behav 9: 261-263, 1978. 64. Pigache, R. M. and H. Rigter. Effects of peptides related to ACTH on mood and vigilance in man. In: Frontiers o f Hormone Research, vol 8, edited by Tj. B. van Wimersma Greidanus and L. H. Rees. Basel: Karger, 1980. 65. Ramaekers, F., H. Rigter and B. E. Leonard. Parallel changes in behaviour and hippocampal serotonin metabolism in rats following treatment with desglycinamide lysine vasopressin. Brain Res 120: 485-492, 1977. 66. Rigter, H. and A. Popping. Hormonal influences on the extinction of conditioned taste aversion. Psychopharmacology 46: 255-261, 1976. 67. Rigter, H. and H. van Riezen. Anti-amnesic effect of ACTH 4-10: Its independence of the nature of the amnesic agent and the behavioral test. Physiol Behav 14: 563-566, 1975. 68. Rigter, H., H. van Riezen and D. De Wied. The effect of ACTH- and vasopressin analogues on CO2-induced retrograde amnesia in rats. Physiol Behav 13: 381-388, 1974. 69. Sandman, C. A., A. J. Kastin and A. V. Schally. MSH and learned appetitive behavior, Experientia 25: 1001-1002, 1969. 70. Sandman, C. A., W. D. Alexander and A. J. Kastin. Neuroendocrine influences on visual discrimination and reversal learning in the albino and hooded rat. Physiol Behav 11: 613-617, 1973. 71. Schulz, H., G. L. Kov~ics and G. Telegdy. Effect of physiological doses of vasopressin and oxytocin on avoidance and exploratory behavior in rats. Acta Physh~l Acad Sci Hung 45: 211-215, 1974. 72. Schwartz, J. C., B. Malfroy and S. De La Baume. Biological inactivation of enkephalins and the role of enkephalindipeptidyl-carboxypeptidase ("enkephalinase") as neuropeptidase. L(~" Sci 29: 1715-1740, 1981.

VAN W 1 M E R S M A G R E I t ) A N I S S t:1 4 1

73. Schwarzberg, H., G. L. Kovfics, G. Szab0 and (;. letegdy, Intraventricular administration of vasopressin and oxytocin effects the steady state levels of serotonin, dopamine and norepinephrine in rat brain. Endocrinol l:xp 15: 7s-80, 1981. 74. Sterba, G., W. Naumann and G. Hoheisel. Exohypothalamic axons of the classic neurosecretory system and their synapses. Prog Brain Res 53: 141-158, t98(I. 75. Steiner. D. F.. W. Kemmler, H. S. Tager and J. D. Peterson. Proteolytic processing in the biosynthesis of insulin and other proteins. Fed Proc 33:2105-2115, 1974. 76. Tanaka, .M., E. R. de Kloet, D. De Wied and D. H. G. Vcrsteeg. Arginine~-vasopressin affects catecholamine metabolism in specific brain nuclei. Lff~, Sci 20: 1799-1808, 1977, 77. Tanaka, M.~ D. H. G . Versteeg and D. l)e Wied, Regional effects of vasopressin on rat brain catecholamine metabolism. Ncurosci Left 4: 321-325, 1977. 78. Telegdy, G. and G. Kov:ics. Role of monoamines in mediating the action of ACTH, vasopressin and oxytocin. In: Central Nervous System &f[~wts o f Hypothalami( Horm,m<~ and Other Peptides, edited by R. Collu, A. Barbeau, J. R. Ducharme and J. G. Rocheforl. New York: Raven Press, 1979. 79. Telegdy, G. and G. Kovfics. Role of monoamine in mediating the action of hormones on learning and memory. In: Brain Mechanisms in Memory and Learning. From Sin,uh' Neuron tf) Man. edited by M, A. B. Brazier. New York: Raven Press, 1979. 80. Urban, I. J. A. Intraseptal administration of vasopressin and oxytocin affects hippocampal electroencephalogram in rats. Exp Neurol 74: 131-147, 1981. 81. Versteeg, D. H. G. Effect of two AC'lH-analogs on noradrenaline metabolism in rat brain. Brain Res 49: 483--485, 1973. 82. Versteeg, D. H. G. and R. J. Wurtman. Effect of ACTH 4-10 on the rate of synthesis of [:~H]catecholamines in the brains of intact, hypophysectomized and adrenalectomized rats. Brain Res 93: 552-557, 1975. 83. Versteeg, D. H. G., M. Tanaka and E. R. de Kloet. Catecholamine concentration and turnover in discrete regions of the brain of the homozygous Brattleboro rat deficient in vasopressin. Endocrinology 103: 1654-1661, 1978. 84. Versteeg, D. H. G., E. R. de Kloet. Tj. B. van Wimersma Greidanus and D. De Wied. Vasopressin modulates the activity of catecholamine containing neurons in specific brain regions. Neurosci Lett I!: 69-73, 1979. 85. Walter, R. Identification of sites in oxytocin involved in uterine receptor recognition and activation. Fed Proc 36: 1872-1878. 1977. 86. Walter, R., J. M. van Ree and D. De Wied. Modification of conditioned behaviour of rats by neurohypophyseal hormones and analogues. Proc Natl Acad Sci USA 75: 2493-2496, 1978. 87. Wang, S. Synthesis of desglycinamide lysine vasopressin and its behavioral activity in rats. Biochem Biophys Res ('ommun 48: 1511-1515, 1972. 88. Weiss, J. M., B. S. McEwen, M. T. Silva and M. Kalkut. Pituitary-adrenal alterations and fear responding. A m ,I Physiol 218: 864-868, 1970. 89. Wimersma Greidanus, "Ij. B. van. Effects of MSH and related peptides on avoidance behavior in rats. In: Frontiers o.fHormone Research. vol 4, edited by F. J. H. Titders, D. F: Swaab and Tj. B. van Wimersma Greidanus. Basel: Karger, 1977. 90. Wimersma Greidanus. Tj. B. van. Disturbed behavior and memory of the Brattleboro rat. Ann N Y A c a d Sei 394: 655-662, 1982. 91. Wimersma Greidanus, Tj. B. van and D. De Wied. Effects of systemic and intracerebral administration of two opposite acting ACTH-related peptides on extinction of conditioned avoidance behavior. Neuroendocrinology 7: 291-30t, 1971. 92. Wimersma Greidanus, Tj. B. van and D. De Wied: Dorsal hippocampus: a site of action of neuropeptides on avoidance behavior? Pharmacol Biochern Behav 5: 29-33, 1976.

SITES OF ACTION OF NEUROPEPTIDES

93. Wimersma Greidanus, Tj. B. van and D. De Wied. Modulation of passive avoidance behavior of rats by intracerebroventricular administration of antivasopressin serum. Behav Biol 18: 325-333, 1976. 94. Wimersma Greidanus, Tj. B. van, B. Bohus and D. De Wied. Effects of peptide hormones on behaviour. Excerpta Medica lnt Congress Series no. 273, 197-201, 1973. 95. Wimersma Greidanus, Tj. B. van, B. Bohus and D. De Wied. Differential localization of the influence of lysine vasopressin and of ACTH 4-10 on avoidance behavior: A study in rats bearing lesions in the parafascicular nuclei. Neuroendocrinology 14: 280-288, 1974. 96. Wimersma Greidanus, Tj. B. van, J. Dogterom and D. De Wied. Intraventricular administration of anti-vasopressin serum inhibits memory consolidation in rats. Life Sci 16: 637644, 1975.

463

97. Wimersma Greidanus, Tj. B. van, B. Bohus and D. De Wied. CNS sites of action of ACTH, MSH and vasopressin in relation to avoidance behavior. In: Anatomical Neuroendocrinology, edited by W. F. Stumpf and L. D. Grant. Basel: Karger, 1975. 98. Wimersma Greidanus, Tj. B. van, B. Bohus and D. De Wied. The role of vasopressin in memory processes. Prog Brain Res 42: 135-141, 1975. 99. Wimersma Greidanus, Tj. B. van, G. Croiset, E. Bakker and H. Bouman. Amygdaloid lesions block the effect of neuropeptides (vasopressin ACTH 4-10) on avoidance behavior. Physiol Behav 22: 291-295, 1979. 100. Wimersma Greidanus, Tj. B. van, G. Croiset and G. A. Schuiling. Fornix transection: discrimination between neuropeptide effects on attention and memory. Brain Res Bull 4: 625-629, 1979.