Effects of acute and chronic haloperidol treatment on the concentrations of immunoreactive β-endorphin in plasma, pituitary and brain of rats

Copyright

002X-3YOX,X?.l~ZOl47-08103 OO,O 0 1982 Pcrgnmon Press Ltd

EFFECTS OF ACUTE AND CHRONIC HALOPERIDOL TREATMENT ON THE CONCENTRATIONS OF IMMUNOREACTIVE (J-ENDORPHIN IN PLASMA, PITUITARY AND BRAIN OF RATS t’.

Department

HiiLLT

and M.

B~‘RC;MAN~

of Neuropharmacology, Max-Plan&Institut fir Kraepelinstrasse 2. D-8000 Miinchen 40. F.R.G.

Psychiatric,

Summary Halopcridol (0.03 -3 mg:kg) dose-dependently increased the plasma concentrations of immunorcactivc /j-endorphia (ir-{i-END) without changing the concentrations of ir-P-END in the adenohypophysis or the lleilrointerm~diate pituitary of rats. Elevated levels of ir-/i-END in plasma were also found after chronic treat~~e~~t\slith h~~loperi~~~l (I mg:kg per dayi for 3 weeks. The long-term treatment.

ho\vc\er. caused a selective increase (60”,,) of the ir+END concentrations in the neuroint~rmediate pituitary without changing that in the adenohypophysls. Significantly elevated levels of ir-P-END were also found tn the hypothalamus and the septum. Gelchromatographic separation of the plasma components reacting with the [Lendorphin antiserum revealed that both the acute and chronic haloperidol treatment increased the plasma concentrations of immunoreactive material with the molecular si7e of /f-endorphin and /Llipotropin. This indtcates that. at least, part of ir-/l-END released by halopcridol Into plasma ib of adcnohypophyscal origin, since no material with the molecular size of /I-lipotropin has been found in the neurointcrmediate pituitary

Previous studies have indicated that neuroleptics can aftict the release a&or biosynthesis of endorphins in the brain and pituitary of rats. Dopamine inhibits the release of /I-endorphin from isolated neurointermediatc lobes or intermediate lobe cells of rat pituitaries, an elTect which is rcvcrsed by the dopamine receptor antagonist haloperidol (Przewlocki. Hiillt and Herr, 197X; Vale. Rivicr. ~~ttillctnill and Rivier. 1979; Vermea Mulder. Smelik and Tiiders. 1980). Acute treatment of rats with haloperidot has been shown to increase the plasma levels of immunoreactive x-melanocyte-stimulating hormone (a-MSH), adrenocorticotropin (ACTH), /I-lipotropin (/I-LPH) and /I-endorphin (Usategui, Oliver. Vnudry, Lombardi. Rozenberg and Mourrc. 1976; Penny and Thody. 1978: Penny. Thody and Shuster. 1979: Giraud, Lissitrky, ConteDcvols. Gillioz and Oliver. l9SO}. The c~~ticomitant elevation in the plasma concentrations of these peptides is explained by the observations that all these peptides derive from a common precursor molecule (Mains. Eipper and Lmg. 1977) and arc localized within the same vesicles of the pituitary cells (Weber. Voigt and Martin, 197X). Chronic treatment of rats writh haloperidol and othel- neuroieptic drugs over a period of 1 3 weeks has been shown to significantly increase the concentrations of rncthi~~t~inc-(met)enkeph~tlill in the corpus striatum and the nucleus accumhens (Hong. Yang, t:ratta and Costa, 1978). Evidence has been provided that the increased striatal levels arc due to an in-

creased biosynthesis of the peptide (Hong, Yang, Gitlin, di Guilio, Fratta and Costa. 1979). Moreover. an increased potassium-evoked release of met-enkephalin from striatal slices of chronically haloperidol-treated rats has been reported (Osborne and Herz, 1980). A significant increase in the level of the total opiate activity in the brain of rats measured by radioreceptor assay was also observed after chronic chlorpromazine treatment (Wise and Stein. 19?9). This raises the possibility that the thcrttpeutic action of neuroleptics in schi7ophrcnic patients might be associated with changes in endorphincryic activity. In fact, evidence for an involvement of endorphins in schizophrenia has been provided by Tcrenius. Wahlstriim, Lindstriim and Widerlov (1976) who reported that schizophrenic patients exhibited elevated levels of ~ndorphins (rn~isllred by r~~diorcceptt~r assay) in the cerehrospinal Ruid which returned to normal after neuroleptic treatment. it w:as the purpose of the present study to investigate whether chronic haloperidol treatment of rats also altered the levels of P-endorphin. an opioid peptide with a biosynthetic pathway different to that of the cnkephalins (Lewis. Stern. Kimura, Rossier. Stein and Udenfriend. 1980) in brain and pituitary. In addition, the effect of acute and chronic ~i~lloper~d[~l treatment of rats on the release of /I-endorphin into the blood was studied.

-._

Male Sprague Dawley rats (Jautz, Kisslegg. F.R.G.), weighing 200-220 g at the start of the experiments. were used. H~ti~~peridol or 0.9”,, saline were

Key

words:

Haloperidol,

~-endorphin,

fi-lipotropin.

RIM-HODS

a-

MSH. ACTH. hypothalamus. pituitary. plasma. 47

148

V. HijL1.Tand M. BIRGMANY

administered intrapcritoneally to different groups of rats in a volume of 0.5 ml. In the acute experiments. increasing doses of halopcridol (0.03 3 mg,‘kg) were administered and the rats decapitated 30 min later. Furthermore. in a time -course study. rats rcceiced a constant dose of 3 mg;kg haloperidol or 0.9”,, saline and were killed 30. 60 and I20 min later. In the chronic cxpcriments, the rats wcrc treated for 3 weeks with daily iii.jections of halopcridol (I mp kg) or 0.9”,, saline.

After decapitation. the trunk blood of each rat was collected (5~-7 ml) in pre-cooled polypropylene tubes. each containing 10 mg EDTA. Plasma was obtained by centrifuging the tubes at 1000~ for 15 min at 4 C. Thereafter. the plasma samples were placed on dry-ice and stored frozen at -30 C prior to radioimmunoassay (RIA). Immediately after decapitation, the brain was removed and the hypothalamus and the septum dissected out. The pituitary was then divided in bird/ into the anterior lobe and the neurointermediate lobe lobe) (= posterior lObe with a dhering intermediate under microscopic guidance. All tissue parts were transferred to pre-tared Eppendorf polypropylene tubes and immediately weighed. Thereafter. a 600 /II aliquot of hot 0.1 N HCI (96 C) was added followed by an incubation at 96 C for IO min. After homogenization. the tissues were centrifuged (20.000 8 for I5 min) and the supcrnatants stored frozen at - 30 C. After thawing of the brain samples, the supernatants were adjusted to pH 7.5 with NaOH and recentrifuged. The acid supernatants of the pituitary lobes were adequately diluted with RIA buffer without pH adjustments.

Aliquots. 0.05 0.1 ml. of the tissue extracts or the plasma samples were measured for immunoreactive /&endorphin (ir-P-END) or. in some cases, for immunoreactive (ir) ACTH according to a RIA protocol as described previously (Hiillt. Przewlocki and Herz, 1978). For the P-endorphin RIA antiserum dopamine was used. It recognized human /I-endorphin and human P-LPH with the same high avidity (detection limit about 5 fmol;tube). The antiserum was characterized previously (Hiillt, Gramsch and Herz. 1979). Opioid peptides which originate from the adrenal medulla contain the amino acid sequence of metenkephalin and have been show/n to circulate in the blood (Yang, Hexum and Costa, 1980). Since P-endorphin also contains the amino acid sequence of metenkephalin. a putative crossreactivity of these peptides to the /i-endorphin antiserum might exist. Howp-cndorphin could be ever. no immunoreactive detected in rat adrenal medulla extracts (detection limit 0.2 pmol,:g) with [j-endorphin antiserum dopamine. There was also no interference by haloperidol in the /I-endorphin RIA at concentrations up to

10~ ’ M. The antiserum directed agamst ACTH, LJ amide recogni7cs human ACTH, Jt) and r-MSH with identical avidity (dctcction limit 5 fmol; tube) and has been previously characterized (Grams& Klcber, Hiillt. Pasi. Mehracin and Hcrz. 1980). Synthetic human /&endorphin was used as a standard. Since rat /&endorphin is different from human /I-endorphin. the val~~cs arc expressed as human /I-endorphin cquivalcnts (Rubinstein. Stein and 1 ‘dcnfriend. 1977). For determination of ir-/j-END in plasma. standal-ds bvcre measured in the presence 01 0. I ml aliquots of rat plasma in which /i-endot-phin and /I-LPH had been removed by adsorpGon lo siliclc acid (Hiillt (‘I t/l., 1978). The RIA-procedure for the determination of immunoreactive met-enkcphalin has been described 117detail (Duka. Htjllt. Pr/ewlocki and Wesche. 1978). The antiserum used exhibited a high specificity for met-enkephalin: the cross-reactivity of Icucine-enkephalin was below I”,,.

Prior to geltiltration. equal plasma aliquots from X to I2 rats were mixed together to give a final 10 ml pool. /&Endorphin-immunoreactivc substances were extracted by adsorbing the pcptidcs to 0.5 g silicic acid powder followed by desorption with acetone: 0.1 N HCI (20/80 voljvol) as previously described (H6llt et al.. 1978). The recovery of the extraction was /i-endorphin aind 55 + 5”,, (II = 4) for human 29 + 4”,, (II = 4) for human /I-LPH. as assessed by adding 500 fmol of the peptidcs to IO ml /Gendorphin b-LPH-free plasma followed by extraction and radioimmunoassay. The acid acetone extract was lyophili7ed. redissolved in I.2 ml RIA bufl‘cr (= buffer “D” according to Guillemin, Ling and Vargo. 1977). Equal aliquots of the pituitary extracts weI-e appropriately diluted with RIA buffer and pooled together to give a final volume of 1.2 ml. One ml of the plasma or pituitary extracts were subjected to a Scphadck G-50 superfine column (0.9 x 95 cm) and cluted in RIA buffer at a flow rate of S ml,‘hr at 6 C. 0.9 ml fractions were collected. Two 0.35 ml aliquots of each fraction ucrc measured for ir-/&END in the plasma: two 0.2 ml aliquots were measured for ir-/$-END and two 0.2ml aliquots for ir-ACTH in the pituitary extracts. The column was calibrated with human /{-endorphin. human /I-LPH. human ACTH and X-MSH: the void volume was determined wjith dextran blue.

Haloperidol was a gift from Janssen Pharmaceutica. Becrse. Belgium: human P-LPH was kindly donated by Dr. C. H. Li, San Francisco, U.S.A.: human ACTHI_,, was a generous gift from Dr Rittel. CIBA GEIGY AG. Basle. Switzerland; human /3-endorphin and r-MSH were obtained from Peninsula. San Carlos. U.S.A.; silicic acid (Kiesel Gel. gefBllt. trocken) was obtained from Merck. Darm-

Haloperidol

increases /I-endorphin

03

10

haloperldol

stadt.

noassay F.R.G.

F.R.G.;

the

procedure

30

1mgl

kg)

30 min after intraperitoneal injection or saline (open bar). Mean i SEM of 8 rats **P -c0.01 :***P -c0.001 vs saline injected controls (Student’s t-test).

Fig. I. lmmunoreactive

ing doses

149

levels

/j-endorphin

of haloperidol

chemicals

were

from

(hatched

in plasma of rats

bars)

used for radio-immuSigma. Taufkirchen.

HESC I.TS

Figure I shows the levels of ir-/&END in plasma 30 min following intraperitoneal injection of increasing doses of halopcridol into rats. As compared to the levels in saline-injected control rats. there was a dosedependent increase in the plasma levels or ir-/&END which became significant at a dose of 0.1 mg/kg haloperidol. The time course of the plasma levels of ir-P-END after the injection of a large dose (3 mg/kg) of haloperidol is illustrated in Figure 2. Maximum levels of ir-P-END in plasma were seen 30 min following the drug administration and remained significantly elevated over a period of 2 hr as compared to that of saline-injected rats. No significant change of ir-/?END in both pituitary lobes of the haloperidoltreated rats as compared to control rats could be detected at 30, 60 or 110 min.

of increas-

*P <:0.05:

Figure 3 depicts the separation profiles of the immunoreactive components after gelfiltration of plasma of rats 30 min after injection of 3 mg,‘kg haloperidol or saline. Three immunoreactive components with different molecular sizes were seen. The smallest migrated with human /Gendorphin standard; the second species eluted somewhat later than human [I-LPH. The component with the highest molecular size eluted immediately after the void volume. There was no major qualitative difference in the distribution profile of the immunoreactive components in plasma between drug-treated and saline-treated rats. Thus. acute haloperidol administration appears to cause a parallel elevation of all three immunoreactive components in the plasma.

In contrast to the acute treatment. chronic administration of haloperidol (1 mg;kgiday) over a period of 3 weeks caused significant elevation in levels of ir-/iEND in the neurointermediate pituitary (about 607,), the hypothalamus (about 30”,,) and the septum (40”~ (see Table I). whereas the levels of ir-P-END in the adenohypophysis were unchanged. Significantly elevated levels of ir-P-END were also observed in the

im

time

(min

)

Fig. 2. Time-course of immunoreactive fi-endorphin in plasma of rats after intraperitoneal injection of haloperidol (0) or saline (0). Mean + SEM of 8 rats, *P < 0.02 (Student’s f-test).

150

V.

HijLLT

and M.

BFKGMA>N

“0

R,LPH

I$, END

1

I

I

Fig. 3. /~-Endorphin-like immunorcactive components in rat plasma after- acute treatment with haloperldol (0) or saline (0). Ten ml plasma pools were obtained by mixing equal plasma aliquots of 8 rats uhich had been mjected tither with 3 mg, kg haloperidol or saline 30 mln before dccapitatlon. The plasma samples were extracted. subjected to gelfiltration on a Sephadex G 50 column and the fractions assayed for immunoreactlve /I-endorphln. as dcscrlbcd in the Methods. The column uas calibrated with dextran-hluc for the void volume ( = V,,) human /I-lipotropin ( =/j,,-LPH) and human /j-cndorphin ([j,,-END): V, = total volume of the column. The values have not been corrected for recovery of the extraction procedure.

plasma. The marked increase (about loo”,,) of the levels of immunoreactive met-enkephalin after the chronic haloperidol treatment confirms the original findings of Hong c’t trl. (1978). Ir-ACTH was also measured in the pituitary lobes. Like ir-/S-END. the chronic drug treatment induced a signiticant increase of about 60”,, of ir-ACTH in the neurointermediate pituitary without changing that in the adenohypophysis. Figure 4 compares the chromatographic profiles of ir-P-END and ir-ATCH in the neurointermediate pituitaries of rats chronically treated with either

v\rj~PH

;-END

haloperidol or saline. All ir-P-END co-elutes with human /Gendorphin standard and all ir-ACTH comigrates with x-MSH standard. Both of the pepttdcs were increased after chronic halopcridol treatment. The immunoreactive components in plasma of chronically haloperidolor saline-treated rats sepurated by gelfiltration are shown in Figure 5. Again 3 immunoreactive species were separated eluting in the same fraction as those shown in Figure 4. Chronic haloperidol treatment increased the concentrations of all 3 components in the plasma to a similar extent.

“0 11

h-ACTH

a-MSH 1

Fig. 4. /j-Endorphin-like and ACTH-hke immunoreactive components in neurointermediatc pituitaries of rats either chronically treated with haloperidol (0) or saline (0). Equal aliquots of extracts of 17 neurointermediate pituitaries of rats either treated with haloperidol (1 mgjkg!day) or saline for 21 days were mixed together, subjected to gelfiltration on a Sephadex G 50 column and the fractions assayed for immunoreactive /j-endorphin and ACTH, as described in the Methods. Arrows indicate the void volume (= VJ. human P-lipotropin ( = b,,-LPH), human /I-endorphin ( = /I,-END), human ACTH ,_39 ( = ACTH) and r-MSH.

The

results

presented

provide

with

of

dependent

release of ir-/l-END

blood

rats

circul~~t~~~ll, The

elcration

of plasma

previously Gr;wd

(3~it/.

for

the pltuitaq

is \ci-y stniilx and

rats.

howver,

concentrations

haloperidol

are

Injection.

of ir-/l-END

from

not

altered

indicating

tide. or a rapid

pttuitary 2 hr

Separation

to GIII\IC;I

is too small

pools of the pcpplace rcstorinp

takes

of

the

itilmiinoreactive

indicates

an increase

that

components

smaller

than human P-LPH.

represent human

P-LPH /GLPH

of

the

This

rat

and Mains.

(Eippcr

just

behind

is

\iolumc

/GLPH

P-LPH-like

of the column

hound

to

of [Cendorphin

plasma

plasma appears to be sccretcd from previously

shwn

in

consist

with /i-LPI1

(ratio /kLPH

/I-endorphin 1:

has bwn

ii-LPH

both

;md

as the predominant pcptidc

1980). In contrast. k-/l-END tary of rats represents

of

the

the ~~~icti[~pitlii-

in the ucicnol~!poph~si~ to

ji-endorphin.

molecular SIX

protans.

~~irn~~~~~)re~~ct~~c material

tary. since ir-/l-END

than

immuiiorc~~cti\e component

might either represent precursor kxms (kndorphin

w~aller

lY701. In addition.

molccul~i~- si.w material

the k&i

was also observed. This

;III ml-

site slightly

suh~tancc mtght

uhtch

of an even hiphcr

an increase

eluting

in not

of an i~~~nil~i~~rc~lcti~c material with

munoreactive material with ;I niolccular

The

the

~~~~l~~perid~~linducts

the molecular size of ~~-cnd~~rpliii~.but alw of

or

of ;il‘tcr

ir-/&END.

the plasma only

h>

ol’ ir-/i-END

that c‘lthcr the rclcasc

the pituitarv rosynthcsis

to that

uithin

dctectuble decrease in the pituitary released

into

ir-ACTH

in the adeno- and the nellroiritcrrnedlate the

acute

a dosc-

of the ~~~11t)pcrid~~l

ir-/l-END

(1980). The

that

GIUXS

from

time-course

ir-/i-END

reported

evidcncc

halopcridol

treatment

1 to

I : 1 : Grams&

VI (I/..

in the intcrmedlatc pitui-

e\cliisi\elj

of /kndorphm

material with the

(Fig. 4).

The increased levels of immunorcactitc material m the plasma &cr

/I-LPH-like

acute halopsr~dol

ment indicate that the ncuroleptic partly. the secretion of ir-/l-END

from

trc’at-

at Icaat

the adcnohy-

hl

earlie

reports in rats in which l~~~l(~pcri~i~~l and other

ncuro-

pophysis.

assumption

inducts.

This

is supported

Icptics have been shown to increase the plasma lewls of AC’TH Thody.

and /I-LPI-I

197X: Giraud

tides are virtually

(de Wind.

lYh7:

demonstrate

that r-MSH

intermediate

pituitary

to treatment

ments

which

from

into blood circulation of rath nith

1978). Since x-MSH of

reports

can he rclcawd

xc

the same precursor

protein

and

Penny

and /I-endorphm

the

111 rt’-

halopcridol

other neuroleptlc drugs (for rcftrenccs Thody.

mci

absent in the intermediate pituttary.

On the other hand, there are vxcral

sponse

Penny

cv irl.. IYXO). both of thcsc pep-

xc

(Mains

and frag-

C! ~rl..

1977) and occur in the same \es~clcs gvithin the intcrmediate lobe cells of the rat pituitary and Voigt, peptides

19791,

in

a concomitant

response

to

certain

(Martin,

secretion

Weber of

both

pharmacological

152

V. Hiit.1.r and M. Bi

KC;hlANN

"1

Fig. 5. /j-Endorphin-like immunoreactive components in plasma of rats either chronically treated with haloperidol (0) or saline (0). Ten ml plasma pools were obtained by mixing equal plasma aliquots of 12 rats which had been treated either haloperidol (I mg/kg;day: 0) or saline (0) for ?I days. The plasma samples were extracted. subjected to gelfiltration on a Sephadex G 50 column and the fractions assayed for immunoreactive /I-endorphin. as described in the methods. V,, = void volume; /I,,-LPH = human /&lipotropin: /j,,-END = human P-endorphin: V, = total of the column. The values have not been corrected for recovery of the extraction procedure. stimuli might bc anticipated. Moreover, there is much evidence that release of both peptides from the rat intermediate pituitary is under the inhibitory control of dopaminc fibrcs of the hypothalamus (Tilders and Smelik. 1977); Prrewlocki. Gramsch, Hiillt, Millan. Osborne and Herr. 1980). III rif~o release studies have shown that the release of P-endorphin and r-MSH from isolated neurointcrmediate pituitaries can be inhibited by dopamine receptor agonists (Bower, Hadley and Hruby, 1974; Tilders and Smelik, 1977; Przewlocki et trl.. 1978). It is. therefore, not unreasonable to assume that the elevated levels of ir-/l-END in the plasma of rats after acute treatment with halopcridol results from the secretion of /I-endorphin from both the adenohypophysis (together with that of /I’-LPH and ACTH) and the intermcdiatc pituitary (together with that of x-MSH).

Plasma levels of ir+END were still found to be increased after prolonged treatment of rats with haloperidol (I mg/kg per day) over a period of 21 days. This finding is indicative that is no substantial development of tolerance to the effect of chronic haloperidol on the secretion of P-endorphin from the pituitary. Similar observations have been made for prolactin. Hypcrprolactinaemia. induced in rats by haloperidol. was still observed after 30 days of drug treatment (Scapagnini. Rizza. Drago. Canonico, PellegriniQuarantotti. Ragusa, Clementi. Prato. Marchetti and Gessa, 1980). On the other hand. tolerance has been shown to occur quite rapidly to the effect of haloperidol on dopamine turnover in the striatum (Lerner, Nose, Gordon and Lovenberg. 1977). This difference in the development of tolerance appears to reflect differences between the regulation of dopaminergic neurones in

the tubcroinfllndibular and nigrostriatal systems (for review see Annunriato, lY7Y). III contrast to the acute treatment. the chrome administration of halopcridol also increased the levels of ir-P-END and ir-ACTH in the tntcrmediate pituitar) by about 60 go”,, without changing the tevcls in the adenohypophysis. Gclfittration of the immunoreacrive components in the intermediate pituitary re\ealcd that the long-term haloperidol treatment exclusively increases the concentrations of matci-ials ~+ith the molecular size of /I-endorphin and x-cndorphin and r-MSH. Isolated neurointermediate lobes of rats. treated chronically with haloperidol, exhibited a significantly higher release of ir-P-END into the incubation medium as compared to that of the salincinjected control rats (Hiillt. unpublished data). The elevated level of ir-P-END in the intermediate pituitary. associated with an increased release of the pcptide. is indicative that chrome halopcridol trcatmcnt increases the biosynthesis of ir+END in the intermediate lobe cells of the rat pituitary. In fact. it was recently demonstrated that long-term drug trcatmcnt increases the biosynthesis of the /f-endorphin precursor protein by 60 lOO’Y,, without altering the processing of the precursor into /j-endorphin (Hiillt. Prrewtocki. Bergmann. Haarmann and Duka. 19X0). Rcccnt cxperiments in this laboratory provide strong c\ idcncc that chronic treatment of rats with halopcridol and other neurolepttcs increases the messenger RNA xtivity coding for the /&endorphin precursor in the intermediate pituitary (Hiillt. unpublished). The increased biosynthesis of /i-endorphin in the intcrmediate pituitary, but not in the ~tdcliohypophysis. after long-term treatment with halopcridot might suggest a selective release of the peptide into the circulation from the intermediate pituitary. Gelfiltration of the immunoreactive components in plasma of the

Haloperidol

inct-eases

chronic haloperidol-treated rats, however, also shows elevated levels of P-LPH-like material. This finding indicates that the chronic drug treatment induces, at least partly. the release of ir-/&END (comprising /&LPH and [I-END) from the adenohypophysis. This assumption appears to be supported by studies in human subjects. showing that after chronic treatment of schizophrenic patients with neuroleptics. the levels of ir-/i-END in the plasma were increased (Emrich. Hiillt. Bergmann, Kissling, Schmid. v. Zerssen and Herz, 1980). The ir-/GEND in human plasma is of adenohypophyseal origin, since the human pituitary is devoid of any intermediate lobe. Increased plasma Icvels of ir-/&END in schizophrenic patients after long-tcrtn neurolcptic treatment can also be tnferrcd from previous studies, reporting a stimulated secretion of ACTH after chronically ncuroleptic therapy of schizophrenic patients (Brambilla. Guerrini. Guastalla. Rokese and Riggi, 1975). In addition to the intermediate pituitary, long-term treatment of rats with haloperidol significantly increases the levels of ir-/&END in the hypothalamus, an area which contains the /Gendorphin producing cells within the arcuate nucleus and the septum, an area which contains exclusively fibers of the /j-endorphinergic neurones (Bloom. Battenberg. Ross&, Ling and Guillemin, 197X). It might be not unreasonable to assume that, as in the nurointermediate pituitary. the increased levels of ir-P-END in the brain after chronic haloperidol treatment reflects an increased biosynthesis of the peptide. Thus, the present results provide evidence that the chronic haloperidol treatment of rats not only causes enhanced levels of met-enkephalin in the corpus striaturn and the nucleus accumbens. as first reported by Hong (‘I trl. (197X). but also increases the levels of /I-endorphin in the hypothalamus. in the septum and in the neurointermediate pituitary which possibly reflects an increased activity of the /j-endorphinergic system.

The increasing effect of chronic neuroleptic treatment on the levels of at least two different endorphnergic systems might be indicative that the neuroleptic drugs exert their effects in schizophrenic patients by mechanisms involving endogenous opioid peptides. However. a central role of endorphins in the pathogenesis of schizophrenia appears to be unlikely. since the administration of the opiate-antagonist naloxone to schizophrenic patients chronically treated with neuroleptics did not cause any deterioration of the mental illness (Emrich e’t trl., 1980). A series of experiments using naloxone in schizophrenic patients have yielded tither negative results or, particularly with large doses of naloxone. a tendency to improve the symptoms of the mental illness (for review see Vercbey. Volavka and Clouet. 1978).

,~~~~rl,~l~lc~l~/t~~l~~~~~ The authors thank Dr G. T. Shearman for stylistic reblsion of the English text.

153

/j-endorphin Icvels REFE:RE:SC‘ES

AnnunGto. lar

and

L. 11979). Regulation nigrostriatal systema.

of the tuberoinfundibuNc,lr~oc~r~tloc,r~~t~)l(j~/~ 29:

66 76. Bloom. F.. Battenberg. F.. Rower. J.. Ling. N and Guillemon. R. (197X). Neurons containing /j-cndorphin tn rat brain exists separately from those containing enkephalin : itnmunocytochemical studies. Pwr,. wfn. Acwl. SCi. U.S.A. 75: 1591 1595. Bower. A.. Hadlcy. M. E. and Hruby. V. 1. (lY74). Biogenic amines and control of melanophore stimulating hormones release. Sc,irrtw 184: 70 72. Bramhilla. F.. Guerrini. A.. Guastalla. A.. Rovese. C. and Rtggt. F. (1975). Neurorndocrine effects of halopertdol thcraphg tn chrome achi7ophrema. P\~,c,lt~,/Jlltr~rl7~~[,~~/~~~/itr. &,,I. 44: I7 22. De Wied. D. (1967). Chloropromarine and endocrine function. Plttrrmtrr~. Rcr.. 19: 25 I 2x8. Duha. Th.. Hiillt. V.. Prlcwlocki. R. and Wcsche. D. (lY78). Di~trihutton of methionineand leuctnc-cnkephalin atthin the rat pituitary gland measured by htghly specific radio-tmmunoassays. Biochrm hio/~l~~.\. Re.5. commlol. 85: I I 19-l 127. Etpper. B. A. and Mains. R. E. 11979). Characterization of mou\e tumor cell /I-lipotropin. J. hioi. Clwrft. 254: 10190 IOIYY. Emrich. H. M., li~~llt. V.. Bergmann. M.. Kissling. W.. Schmtd. W.. \. Zcrssen. D. and Hcrz, A. (1980). Plasma levels of /i-endorphin 111schizophrenic patients: Failure of naloxone to counteract curatt\e effects of neuroletXic

Prcsa, New York. Giraud. P.. Lissitzky, 1. C.. Conte-Devolx. B., Gillioz. P. and Oliver, C. (1980). Influence of haloperidol on ACTH and [I-endorphin secretion in the rat. Eur. J. Pharmuc. 62: 215~217. Gram&. Ch.. Klcber. G.. Hiillt. V.. Past. A.. Mehraein, P. and Herr. A. (1980). Pro-opiocortin fragments in human and rat brain: /j-endorphin and r-MSH are the predominant peptides. Brclin Res. 192: 109 119. Guillemin. R.. Ling. N. and Vargo. T. (1977). Radioimmunoassay for r-endorphin and /j-endorphin. Biochoke. /~wpl~ 1.x Re. Commw~. 77: 36 I 366. Hiillt. V.. Przewlocki. R. and HerL. A. (197X). Radioimmunoassay of P-endorphin: basal and stimulated levels in extracted rat olasma. h’aunvn-Schnliedrhera’s ., Arclt. Phurmac. 303: 171-174. HZillt. V.. Gramsch. Ch. and Her/. A. (1979). Immunoassay of /i-endorphin. In: R[~[lioi,~~,~t~r,~r~[~.\.s~~ \’ of Lhwq.~ untl Hormwic~ irl Ctrr,~/io-l.clsc,lr/~~r hlr,r/ic,iw (Albertmi. A.. Da Prada. M. and Peskar. B.A.. Eds). on. 293 307. Elsevier, ’ North-Holland. Amsterdam. H6llt. V.. Pr7ewlocki. R., Bergmann. M.. Haarmann. I. and Duka. Th. (1980). Increased biosynthesis of /i-endorphin in the pars intermcdta of rat pituttaries after long-term treatment with haloperldol. In: Em/o~qcww trml E\-ogqcw OX\ Opictre Ayoui\r.t ur~d A~ftqor11\/,\ (Way E. L.. Ed.), pp. 315 32X. Pcrpamon Press. Oxford. Hong. J. S.. Yang. H. Y., Fratta. W. and Costa. E. (1978). Rat striatal methionine cnkephalin content after chronic treatment wth cataleptopenic and non-cataleptogenic antischwophrentc drugs. .I. Plwmrrc~. c’\-p. Titer. 205: I41 137. Hong. J. S.. Yang. H. Y.. Gillin. I. C.. di Guilio, A. M., Fratta. W. and Costa. E. (1979). Chronic treatment with halopertdol accelerates the biosynthesis of enkephalins in rat brain. Brcriu Rcs. 160: I92 195. Lcrner. P.. Nose. P.. Gordon. E. K. and Lovenberg. W. (I 977). Haloperidol: Effect of long-term treatment on rat striatal dopamine synthesis and turnover. Science 197: 181-183.

LCM I\;. R Stcnl. A. S.. Kimura, S., Rosslcr. I.. Stein. S. and I’dcrifrwnd. S. (1980). An about 50.000 dalton protein in adrenal medulla. A common precursor of met- and leucnkephahn. .%~iunt~e208: 1459-1461. hla~n. R. E.. Elpper. B. A. and Ling. N. (1977). Common precursor to corticotropin and endorphms. &xc. wtli. .?lhornc, H. and Herz, A. (1980). K +-evoked release of metenhcnhalin from rat striatum irt c,irro: Enict of putative

on the twain.

In :

Crrtrrul

rrr~tl

Prolucfin Funcrion (MacLeod.

Pr~~ip/wrtr~

Re:glultrrior~of

R. M. and Scapagnini. N., Eds), pp. 293 309. Raven Press. New York. Tcrenius, L. Wahlstriim, A.. Lindstriim, L. and Widerlo\. E. (1976).Increased CSF levels of endorphins in chronic psycl1osis. NClII.cxx (Tilders. F. J. H.. Swaab, D. F. and van Wimersma Greidanus. T. B., Eds). Fronr. Norrmm~ Rcs.. Vol. 4. pp. X0-93. Karger, Basel. Usategui. R.. Oliwr. Ch.. Vaudry. H.. Lombardi. J., Rorenherg. J. and Mourre, A. M. (1976). lmmunorcactive z-MSH and ACTH Ic\els in rat plasma and pituitary. f:/lt/f,c,rr/l~,/~,(! 1’ 98: 1X9 196. Vale. W.. Rivler. J.. Guillemin. R. and Rivier, C. (1979). Etl’ects ol” puritied CRI; and other substances on the secretion of ACTH and of /i-endorphin-like lmmunoreactivrtl by cultured anterior or ncurointermediate pituitary cells. In: Ccnirril 4’w ow S1,srcw Eff>rts of ~~~(~~~I~~~[JI?I~~, iJ~it/iwr. 80: XI’ 4P. Hmnom~.~ (Collu at ui.. E&l. pp. I63- 176. Raven Press. Pr/w!(tcki. R.. Hiillt. V. and Her/. A. ( 197X). Suhstanccs New York. Verchey. K.. Volavka. J ;mii Clouet. D. (197X): ~nd~~rpllins in psychiatq. ,,Zrc/zs ;jtw. Pv,ix+ritrr. 35: 877-8xX. Vermcs. J., Mulder. H., Smelik, P. G. and Tilders. F. 3. H. (1980). Differential control of P-endorphin,,P-lipotropin secretion from anterior and intermediate lobes of the rat pituitary gland iu rif,o. h/i, SC;. 27: 1761~ 176X. Weber. E., Voigt. V. H. and Martin, R. (1978). Concomitant storage of ACTH- and endorphin-like immunoreac1‘IIIlctll~ll\ Ill .l’cllrr.,,,,r,‘f,l/~,, unt/ .~~~Itrr,frroi;r)li.ssio,i tibity in the secretory granules of anterior pituitary corti~Marsan. c‘. A. and Tracrvk. W. Z.. Eds). pn. 245-256. cotrophs. Brrriri Rtx IS?: 345 390. Wise. C. D, and Stein. L. (1979). Brain endorphin levels increase after long-term chloropromazine treatment. In: E&wplii!zh iti :\lc~l~/ Nrtrirlr (Usdin. E.. Bunney Jr. W. E. and Kline. N. S., Eds ). pp. 1IS I IX. Macmillan Press. London. Yang. H.-Y. T.. Hexum. T. and Costa. E. (1980). Opioid pcptidcs in adrenal gland. f_+ SC+. 27: 1119~ i 175.