P-2-27 The Citalopram Challenge Test (CCT) as a probe for serotonergic function in depression

283

P-2 Antidepressants: basic and clinical studies that ion-trapping is the main factor of cnloroqulne accumulation, while the binding to membrane phosohohp~dsis is the main factor of desipramme uptake. Single or repeated treatments of rats with desipramine had hardly any effect on the subsequent desipramme uptake by the lung and hver slices, whde accumulation of chloroquine was enhanced m those slices. In conclusion, the extent of the uptake of the studied drugs was tissuespecific, and the contribution of the two uptake mechanisms was strongly drug-dependent Joint administration of two lysosomotropEc drugs m v i v o e g of a tricyclic antidepressant and a phenothiazine neurolept~c, may produce a pharmacokinetic interaction at the levels of cellular distribution and general body distribution, leawng more of a free drug for specific binding sites and decreasing the brain/plasma ratio

References [1l Honegger, UE., Rosc~er. AA ana Wiesmann, dN (1983) Ev=dence for lysoso~ motropic action of deslpramme in cultured human fibroblast J Pharmacol Exp ~[her 225, 436-441 {21 Mac Intyre, A and Cutler, D J (1988) The potential role of lysosomes in tissue d~strl but/on of weak bases Biopharm Drug Disp 9 513 526

Interactions between mianserin and opioid receptor subtype selectivity Chaim G Pick1, Maria M Backer 1,ShaulSchreiber2

1Department of

Anatomy and Anthropology, Sackler School of Medicine, Tet Awv Univers~tx Tel Av/v, Israel, 2 Department of Psychiatry Hadassah University Hospital Ein-Karern, Jerusalem, Israel Mianserin is a tetracyclic antidepressant w~th potent serotonergic proper ties, b e i n g a S H T 1,5-HT 2 and 5-HT 3 receptoragonist It hasnoradrenerglc properties, due to a presynaptic c~2 blockaoe and a strong ant~histamine(H 1 receptor antagonism) effects [for review see Fineberg, and Montgomery, (1991)] In addition to its clinical antidepressant actwlty, mianserin was found to be a potent analgesic in the mouse hotplate assay. There are at least three opioids receptor subtypes capable of el/citing analgesia independentlyr delta (3), kappa (K) and mu (/z) Recently, in all the subtypes multiple subdivisions have been founc. Ifor rewew see Pasternak {1993)] The use of highly selective co/old drugs with minimal side effects, com b/ned with non opiate drugs will help us to treat pain more successfully In thG present study we have examined the analgesic effects of m~anserm alone and in conjunction with op~oid subtypes. Mianserln produced analge sia in the mice hotplate assay, after systemic.~t, and i.c.v administration At doses from i to 25 mg/kg, mianserm produced analgesia in the hotplate test in a dose dependent manner As the mlanserm dose increased beyond 30 mg/kg hotplate latencies returned to baseline, yielding a b~phas;c dose-response curve. The analgesia effect of mianserm was antagon zeal by naloxone (1 mg/kg s.c; P < 0.005)This sensitivity to naloxone indicatec that at least some of the analgesic effect of miansenn is mediated by or" opio~d mechanism of actJor" Morphine (lz agonlst), U50,488H (K1 agonist) and nalorphine 0(3 agonlst) but not DPDPE (~ agonist) significantly sh,fted mianserln dose response curve to the left In addition, /~-FNA(Iz antagonist),norBNI p(1 antagonist) and for less extend naltrindole (~ antagonist) reversed miansenn analgesa The sensitivity of mlanserin analgesia to se lective agonists and antagonists implies /~-opioid, ~1 opioid and hr3-opio,d mechanisms of action and for less extend ~-oploid mechanisms These results suggest a significant role ~or mlanserm in the management of pare

References

[11. The anaigs~c effect of TCAs in human seems to be independent from their antidepressant activity since the doses used for analgesia are lower than those considered effective in the treatment of depression [3]. As the mechanism of analgesic action of TCAs is still obscure, we have sought to ndividuate the neurotransmitter involved in this antinociception. To this end, selective blockers of the following central nociceptive pathways: opioid, serotoninergic, catecholaminergic, histammergic and chloninergic, were used to examine their effect on TCAs analgesia. Results and Conclusion." Both clomipramine (25 mg kg -1 ) and amitriptyhne (20 mg kg -1) subcutaneously administered had a significant effect on the pain threshold of mice tested in the hot-plate and abdominal constriction tests AntinocicelStion peaked after 15 m/n, persisting almost unchanged up to 30 rain and then diminished 45 min after administration. Analgesia was obtained in mice without any visible change in the normal behaviour of animals as resulted in rote-rod experiments where clomipramine and am4triptyline did not significantly modify the time that mice remained on the rota rod. The antinociceptive effect of the t w o antidpressants was not antagonized by the opioid antagonists naloxene (1 mg kg -1 ip.) or the antimusearinic a t r o p i n e ( 5 m g k g 1 i p . ) i n t h e h o t - p l a t e t e s t . On the other hand, 2 m g k g -1 p of reserpine (depletor of 5-HT, catecholamines and histamine), injected twice 48 and 24 h before tricyclic antidepressants, completely prevented the enhancement of the pain threshold in the abdominal constriction test. Since reserpine has a hypothermic activity, a chemical stimulus instead of a thermal one was used to investigate its antagonistic effect. In these experimental conditions reserpine did not produce any reduction in morphine ( 5 m g k g 1 ) o r o x o t r e m o r n e ( 4 0 / z g k g -1) induced antinociception (Fig. 1). Serotoninerg~c. catecholaminergic and histaminergic pathways, all participating in antinociceptive processes, are inactivated by reserpine pretreatment Selective synthesis inhibitors of catecholamines, such as e-methyl ptyros/he (c~MpT), and histamine, such as R-~-methyl-histamine (R-(~-MeHA}, were used to evaluate the involvement of these t w o neurotransmitters in 7CAs analgesia In the mouse hot-plate t e s t o t - M p T ( 2 0 0 m g kg -1 i.p.)and R-~-MeHA (20 mg kg -1 i.p.), injected respectively 2 h and 30 min before the test, did not modify clomipramine and amitriptyline induced antinociception. At the same doses, e-MpT [2} and R-(~-MeHA [3] were able to completely prevent the enhancement of the pain threshold induced by the catecholamines releasing drug amphetamine and the histamine releasing drug thioperamide. These data suggest that the mechanism responsible for clomipramine and amitriptyline analgesia consists on an activation of the serotoninergic system

References I1} Stimmel, B, (1983) In: Pain. Analgesia and Addiction - - The Pharmacological Treatment of Pain, New York, Pavan Press 12] Bartolmi, A. Galli. A, Gherlardini, C, Giotti, A., Malcangio, M, Malmberg-Aiello, P. Zucchi, PL (1987) Antinociception induced by systemic administration of local anaesthetic depends on a central cholinergic mechanism Br. J Pharmacol , 92, 711721 [31 Malmberg-Aiallo, P, Lambetti, C., Ghelardini. C , Giottl, A , Bartolini, A. (1994.) Role of histamine in rodent antinociception Br J Pharmacol . 11 : 1269-1279

~ T h e

Citalopram Challenge Test (CCT) as a probe for serotonergic function in depression

T Kapitany, S.D. Schindler, C. Barnas, A. Neumeister, W. Sieghart, S Kasper. University Hospital of Psychiat~ Clinical Department of General

Psychiatry Wahringer G#rte/18-20, .4-1090 Vienna, Austria

Fineberg, N, Montgomery, S A Oosesslve Compulsive Disorcler A Specific Serotonergic Illness? In Serotonin, Sleep and Mental Disoruer. Edited by C Idz~kowskl and PJ Cowen, Wrightson Biomedical Publishing Ltd. 11991)pp 131 145 Pasternak, G W "Pharmacological mechanisms of opioid analgesia " Clinical Neurophar macology (1993k 1 18

Involvement of serotoninergic System in the analgesic effect of tricyclic antidepressants Department of Prechn/ca/and Clinical Paharmaco/ogy "M A/azz/ Mancmi'; University of Florence, Vla/e G.B Morgagni, 65, 150134 Florence, Italy C. Ghelardini, N Galeotti, A Bartolini

Introduction The tricyclic antidepressants {TCAs) have oeen used for marly years to suppress certain types of pain in h u m a n s These include diabetic neuropathy, postherpetic neuralgia, heauaches, arthritis, chronic back pare cancer, phantom limb pare TCAs we,e reported to be able to ehcit analgesia also in the rat hot-plate and tail flick tests and in the mouse formalin test

The serotonerglc neurotransmission in the limbic system is discussed as a major part in the pathophysioiogy of depression and is a major point of action for pharmacological antidepressant treatment. As a sensitive clinical method to study neurotransmitter systems neuroendocrinological reactions ~o psychopharmacological stimulies are used. /n case of the serotonergic system the acute secretion of prolactin was found as a s0ecific answer :o serotonergic activation. In depressed patients this reaction was blunted 4n terms of a significantly reduced hormonal response. Neuroendocrino logical reactions were studied after stimulation with several compounds hke tricyclic antidepressants (e.g. desipramine and clomipramine), or with _ tryptophan, 5-HT or fenfluramine. In the present study the selective serotonin reuptake inhibitor citalopram was used for neuroendocrinotogical challenge. This substance combines the advantage of a selective serotonergic stimulation with the possibility of intravenous administration, avoiding interindividual differences through enteral absorbtion. Healthy volunteers and patients suffering from an acute episode of major depression underwent the procedure of the citalopram

284

P-2 Antidepressants: basic and clinical studies

challenge test All Subjects were testee under randomized conditions with placebo, with 10 mg and with 20 m g c i t a l o p r a m In intervals of 15minutes bloodlevels of proiactin and cortisol were d r a w n First results ~ndicate that there was a distinct hormonal reaction of c o t tisol and prolactin after stimulation with citalopram in healthy controls A hormonal secretion peak was measured dose-dependent after 60 minutes and 75 minutes respectively We hypothesis that depressed patients exhibit lower hormonal responses which ~n turn might correlate with the treatment response.

help clarify the long-term consequences of serotonin-reuptake blocking vs dopamme-reuptake blocking followed by neradrenergic upregulation,

Fluoxetine, a selective 5-hydroxtryptamine uptake inhibitor, increases the locomotor hyperactivity induced by MK-801, a non-competitive NMDA receptor antagonist J Mai, Z Rogoz, G. Skuza. Institute of Pharmacology Polish Academy of

References

Sciences, 12, Smyrna Sty, PL 31-343 Krak6w, Poland

Laakman G, Gugath M, Kuss H J Zygan K (19841 Comparison ot groth hormone and pro lactin stimulation induced by chlonmipramqne and desipramme in man in connection with chlorimipramine metabolism Psychopharmacology 82:62 67 Kasper S, Vieira A. Schm~dt R, Richter P (1990): Multiple hormone responses to shmulaugh with dl-fenfluramme in patients with maior depression before and after antide pressant treatment Pharmacopsychlat 2376 84 O'Keane ~ McLoughlin D, Dinah TG {1992) D fenfluramme induced prolacbn and cortlsoi release in ma]or depression: response to treatment J Affect Disorders 26 143 ] 50

It was shown previously that some antidepressant drugs, including selective 5-hydroxytryotamine (5-HT) uptake inhibitor, fluoxetine (FLU), enhanced the locomotor hyperactivity induced by the non-competitive NMDA receptor antagonist, MK-801, in rats; the synergistic effect of antidepressant drugs and MK-801 was also observed in behavioural despair test (Maj et al., 1992a, b) A number of own and literature data suggests that the MK-8Ol-induced locomotor hyperactivity results from redirect activation (via blockade of NMDA receptors) of the dopamine system. FLU is a 5-HT uptake inhibitor which shows practically no other properties (Wong et al., 1983). Hence, it may oe supposed that in the interaction mentioned above both dopamine and 5-HT mechanisms are involved, I n this paper the potentiating effect of FLU on the MK-8Ol-induced locomotor hyperactivity was analysed in rats (male Wistar). The FLU + MK-801 hyper!ocomotion was reduced by tropisetron and zacopride (5-HT 3 receptor antagonists) and, to a lesser extent, by ketanserin, ritanserin (both 5-HT 2 receptor antagonists) and NAN 190 (a 5 HT1A and ~-l~adrenergic receptor antagonist} WAY 100135 (the most selective 5-HT1A receptor antagonist). pindolo la 5-HT1A and 5-HTtB receptor antagonist), as well as metergoline or mlanserin (non-selective 5-HT receptor subtypes antagonists), were uneffective Haloperidol, sulpiride, SCH 23390, clozapine and prazosin were able to antagonize (totally or in part) the FLU + MK-801-induced hyperactivity. The hyperlocomotion evoked by MK-801 was also increased by other selective 5-HT uptake inhibitors, citalopram and sertraline. The effect of cltalopram was antagonized by zacopride and ketanserin. Similar potentiating effect was exerted by other 5-HT-stimulants, ie. p-chloroamphetamine, 8-OH DPAT and TFMPR The locomotor hyperactivity induced by dopamine stimulants, amphetamine or apomorphine, was not modified by FLU or CIT FLd increased the release of dopemine (measured by a microdialysis method). Jnduced by MK-801 in the striatum. The above findings indicate that FLU increases the MK-801-induced locomotor hyperactw~ty mainly wa activation of 5-HT 3 receptors and, to a lesser degree, 5-HT 2 o n e s

Effects of paroxetine and bupropion on event-related potentials and spectral frequency J A Camp-Bruno, K. Lifshitz, K. Lee, GS. Linn, R T O'Keeffe

Neurophysio/ogy Department, Nathan Kline institute for Psychtatnc Research, 140 Old Orangeburg Rd, Orangeburg, NY 10962, USA Paroxetine, a selectwe serotonin re uqtake inhibitor, and buproplon, a monocyclic antidepressant appearing to act via monoamlnerg~c mechanisms similar to those of tricyclics, are pharmacologically d~stinct but clinically effective antidepressants The purpose of this study was to determine whether acute and chronic abm nistration of these two compounds yielded electro physiologic differences which would reflect their differential pharmacologic activities by using recordings of electroencephalographic (EEG) activ,ty fo, spectral frequency analyses and auditory event-related potentials (ERP) ~n a population unencumbered oy am/ disease process for which chronic drug admrnistration is practical, namely nonhuman primates Ten Cebus ape//a monkeys were assigned to either a parexebne buprop~on order or the reverse Recordings were obtained under five co" ditions: Basehne, acute oral dose of each drug, and after chronic 5 w K oral oaroxetine (0.7 mg/kg) and b u p r o p i o n ( 7 0 mg/kg) A 1 0 - d a v w a s h o u t separated the crossover from the first to the second drug condition. EEGs were recorded from scalp needle electrodes at Fpz, Cz, P3 P 4 0 z leq outer canthus, and rlgrlt supraorbltal sites Each recording session began with ERPs elicited by tone pips presented in pairs; tones in eacn pair were separated b y 0 5 sec and pairs repeated everySsec(-t-10%) EEG epochs were then collected for spectral analyses Animals next received ' ~g/kg diazepam im, which appreciably decreases artefacts and yields mole re producible recordings After 20m~n the ERP/EEG data collection sequenc.~ was repeated Statisttcal analyses were performed on the p o s t e a z e p a m data. ERPs from Cz-P3 anO Cz P4 were averaged, and peak amplitudes and latenc~esdetermmed for P30, N40, PS0 N100, and P200; ERP peaks to the second tone of each pair occurred 500 msec later and were designated with the suffix S, eg P30S Peakto-peak-amphtude ratios of the first to second tone were calculated for (PS0-N 100)/(PSOS N 100S) and (N 100 P200)I(N 100SP200S). Fast Fourier transforms of [(Cz-Oz) ~ (Cz~P3) + (Ca P4)]/'3 were performed after offline editing to yield power spectra with a resolution of 0 5 Hz, and modal aloha frequency for Cz-Oz. The frequency of the most prominent alpha sinusoidal activity for Cz Oz was determined from the EEG tracings A significant difference b e t w e e r chronic paroxetlne and chron c b~Jgro plon obtained for amplitude ratios {PSONIOO)/IP50S N100S) and (NI00P200)/(N100S-P200S) SFmultaneous separation of paroxetlne, buproplcn, and placebo was attempted for both the acute and chronic conditions usi n g s t e p w i s e d i s c d m i n a n t a n a l y s e s w ~ t h j a c k k n i f i n g For the acute dose, the only discbmmator selected was the latency of NIO0, which was 43% co ~rect; bupropien shortened latency as did paroxetine to a lesser extent After chronic treatment. 70°,/0 correct separation (p = 0.0001) between paroxetine and buproplon was achieved using five vanables: PSO NIO0 amphtbde, (N100-P2OO)/(NIOOS P200S) ratio, eelta power, alpha modal frequency a-d alpha sinuso~dal frequency PS0-N100 amplitude, delta power and aloha modal frequency all moved in different drrections from baseline for oaroxetineand bupropion These data demonstrate thatERP/EEGvar~ablesreflect the pharmacologic d#ferences between these two compounds, and that differential ERP/EEG change associated with paroxetlne and buprop or may

References Mal, J , Rog6z, Z , Skuza, G (1992a) The effects of combined treatment with MK-801 and ant,depressant cJrugs in the forced swimming test m rats Pol J. Pharmacol. Pharm. 44, 217 226 Maj, J , Rogo2z, Z, Skuza G, Sowlr~ska, H (1992b) The effect of antidepressant drugs oq the Locomotor hyperactivity induced by MK-SOl, a non-competitive NM DA receptor antagonist Neuropharmacology 31, 685-691 Worg, DT, 8ymaster, ER, Reid. L.R Threlkeld, PG (1983). Fluoxetine and two other serolon~n uptake inhlbltors without affinity for neuronal receptors Biochem Pharmacol 32, 1287 ! 293

An autoradiographic comparison of aH-paroxetine and 3H-imipramine in human whole brain sections 1 The School of Pharmacy, London, Smithkhne Beecham, United/O'ngdom J Miller N. Bowery, I. Tulloch 1

Paroxetme and imipramine are both antidepressants which are known to act at the 5..HT transporter site by blocking the reuptake of 5-HT into neurons. Imipramqne also acts at noradrenaline receptor sites and less specifically at other receptors in the brain therebyinduc~ng a n u m b e r o f side effects. Paroxet~ne is a highly selective 5-HT reuptake blocker with no significant action at other receptor sites. A comparative study of the autoradiographic distribution of 3H-paroxetine and 3H-imipramine in human whole brain coronal secbons was performed in order to determine the differences and similard~es ~n the binding densities and distribution of these t w o ligands in the human brain Human whole brain coronal sections (40 #m} were cut at - 2 0 ° C onto membrane filter material which acts as a supportive backing material. The sections were incubated in Tris buffer ( 50 mM, oH 7.4) containing 120 mM NaCI and 5 m M KCI. for 15 minutes at room temperature and air-dried The sections were either incubated with 5 nM 3H paroxetine for 2 hours