Effect of chronic antipsychotic drug treatment on preprosomatostatin and preprotachykinin A mRNA levels in the medial prefrontal cortex, the nucleus accumbens and the caudate putamen of the rat

Molecular Brain Research 45 Ž1997. 275–282

Research report

Effect of chronic antipsychotic drug treatment on preprosomatostatin and preprotachykinin A mRNA levels in the medial prefrontal cortex, the nucleus accumbens and the caudate putamen of the rat Monica M. Marcus a , George G. Nomikos a , Anna Malmerfelt a , Olof Zachrisson b, Nils Lindefors b, Torgny H. Svensson a,) a

b

Department of Physiology and Pharmacology, DiÕision of Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden Department of Clinical Neuroscience, Psychiatry Section, Karolinska Institutet, Karolinska Hospital, S-171 76 Stockholm, Sweden Accepted 17 September 1996

Abstract In situ hybridization histochemistry was used to study the expression of preprosomatostatin ŽPPSOM. and preprotachykinin A ŽPPT-A. mRNA in the medial prefrontal cortex ŽmPFC., the nucleus accumbens ŽNAC. and the caudate putamen ŽCP. of the rat after chronic Ž21 days. treatment with the classical antipsychotic drug haloperidol Ž1 mgrkg i.p.., the atypical antipsychotic drugs clozapine Ž15 mgrkg i.p.. and amperozide Ž5 mgrkg i.p.., and the selective dopamine ŽDA.-D 2rD 3 receptor antagonist raclopride Ž2 mgrkg i.p... Whereas amperozide markedly elevated the numerical density of PPSOM mRNA expressing neurons in the mPFC Ž52%., the other drugs did not significantly affect PPSOM mRNA levels in any of the brain regions studied. Amperozide also altered PPT-A mRNA expression in the mPFC, i.e. a decrease Ž22%. was found. Of the other drugs tested only haloperidol significantly decreased PPT-A mRNA levels in the NAC shell Ž14%., in the dorso-lateral CP Ž19%. and in the medial CP Ž15%.. In view of the differences between amperozide and the other drugs studied, as regards both pre-clinical and clinical characteristics, we suggest that the specific effects of amperozide on PPSOM and PPT-A mRNA in the mPFC may be related to its 5-HT releasing action in the frontal cortex, an effect possibly caused by its a 2-adrenoceptor blocking activity. This effect, in turn, may be related to an antidepressant-like action that this compound exhibits in animal studies. The decrease in PPT-A mRNA levels seen after the haloperidol treatment is probably due to its potent DA-D 2 receptor antagonism and may be related to side-effects, rather than therapeutic effects of this drug. Keywords: Haloperidol; Clozapine; Amperozide; Raclopride; Antidepressant drug; Serotonin; Substance P; Somatostatin

1. Introduction Typical antipsychotic drugs ŽAPD., such as haloperidol, are generally considered to exert their clinical effect by blocking dopamine ŽDA. receptors and, thus, affecting DA transmission in the basal ganglia and in limbic regions of the brain. Specifically, the therapeutic action of these drugs has been suggested to be mediated via effects on the mesolimbic and mesocortical dopaminergic systems, while their extrapyramidal side-effects ŽEPS. largely have been attributed to their action on the nigrostriatal DA system. Accordingly, the EPS liability following chronic antipsychotic treatment has been found to be related to the degree of DA-D 2 receptor blockade w18,44,53x in the basal gan-

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Corresponding author. Fax: q46 Ž8. 30-8424.

glia. Whereas a high occupancy of DA-D 2 receptors has been found during treatment with typical APDs such as haloperidol, atypical APDs, such as clozapine, which do not induce EPS, occupy DA-D 2 receptors in the basal ganglia to a lower extent. Several atypical APDs also exhibit higher 5-HT2 than DA-D 2 receptor occupancy in the brain w18,36x. Experimentally, clozapine has been shown to produce a more pronounced effect on the mesolimbic and mesoprefrontal DA systems than on the nigrostriatal DA system w39,40x. Recently, we have shown that atypical APDs with high 5-HT2 and low DA-D 2 receptor affinity, increase DA release to a greater extent in the shell than in the core of the nucleus accumbens ŽNAC., whereas typical APDs, with high DA-D 2 receptor affinity, increase DA release more in the NAC core than in the NAC shell w33x. Several lines of evidence indicate that the NAC shell is functionally associated with the mesolimbic

0169-328Xr97r$17.00 Copyright q 1997 Elsevier Science B.V. All rights reserved. PII S 0 1 6 9 - 3 2 8 X Ž 9 6 . 0 0 2 6 3 - X

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DA system, while the NAC core rather is functionally related to the nigrostriatal DA system w12,13x. Within the DA-innervated regions of the brain, both typical and atypical APDs affect the levels of various peptides as well as their mRNAs in different ways. For example, chronic haloperidol, but not clozapine treatment has been found to decrease both the levels of protachykinin mRNA in the caudate putamen ŽCP. w2,24,32x, and the tissue levels of tachykinins, such as substance P ŽSP. and neurokinin A ŽNKA., in the NAC and the substantia nigra ŽSN. w24,31,48x. Also, preprosomatostatin ŽPPSOM. mRNA has been shown to be decreased in NAC, frontal cortex and medial striatum after haloperidol treatment. Following clozapine, in contrast, the number of positive PPSOM mRNA neurons was not affected, although the intensity of labeling per neuron was increased in the NAC w52x. Accordingly, after haloperidol treatment the tissue levels of somatostatin ŽSOM. have been found to be decreased in the CP, NAC and ventral tegmental area ŽVTA. w7,48x. Indirectly, these studies indicate that DA exerts a regulatory effect on the function of both tachykinin-and SOM-containing neurons in the brain. It is conceivable, therefore, that changes in the genomic expression of these peptides in brain may, in turn, be related to clinically important actions of these drugs. In the present study, in situ hybridization with oligodeoxyribonucleotide probes was used to study expression of mRNAs encoding preprosomatostatin ŽPPSOM. and preprotachykinin A ŽPPT-A. in different rat brain areas after chronic treatment with haloperidol, clozapine, amperozide and raclopride. Haloperidol, a typical APD w29x, is associated with a relatively high EPS liability and a high degree of DA-D 2 receptor occupancy w17,44,53x. Clozapine and amperozide, two atypical APDs, are characterized by a high ratio of 5-HT2 to DA-D 2 receptor affinities. Moreover, clozapine w36x does not induce EPS and can be therapeutically effective also in patients who do not respond to conventional APDs w10,11,26,37,45x. Amperozide w21,54x has in some clinical trials been found to improve both positive and negative symptoms in schizophrenia while showing very low propensity to produce EPS w4,9x. Raclopride is a selective DA-D 2rDA-D 3 receptor antagonist w27,46x and has been shown to produce an effective antipsychotic action, with a very low incidence of acute dystonia w16,35x. In comparison with haloperidol, raclopride appears somewhat atypical both with regard to its EPS liability as well as its pre-clinical profile w1x. 2. Materials and methods 2.1. Animals and tissue preparation Male SD rats weighing 240 " 12 g Žmean " S.D.. ŽB & K Universal, Sollentuna, Sweden. were used. The animals were housed under standard laboratory conditions and

maintained on a 12 h lightrdark cycle Žlights on at 06:00 h., with ad libitum access to food and water. Rats were divided into 6 groups and injected i.p. once a day for 21 days with either saline, amperozide Ž5 mgrkg; Pharmacia., raclopride tartrate Ž2 mgrkg; Astra., vehicle Ž5.5% glucose with a few drops of acetic acid., haloperidol Ž1 mgrkg; Sigma. or clozapine Ž15 mgrkg; Sandoz.. Amperozide and raclopride tartate were dissolved in saline and haloperidol and clozapine were dissolved in a minimal amount of acetic acid with a 5.5% glucose solution added to volume. Vehicle, haloperidol and clozapine solutions were all adjusted to pH 5.5–5.7. The rats were decapitated 24 h after the last injection and their brains were immediately frozen on dry ice and stored at y808C until cryostat sectioning. Coronal tissue sections Ž10 m m thick. for medial prefrontal cortex ŽmPFC. Žat the level of Bregma q3.2. and for nucleus accumbens ŽNAC. and caudate putamen ŽCP. Žat the level of Bregma q1.7. were cut on a cryostat ŽLeitz Kryostat 1720. at y208C Žcoordinates according to Paxinos and Watson w47x.. Two adjacent sections were thawed onto each poly-L-lycine Ž50 m grml.coated slide. 2.2. In situ hybridization The tissues were fixed in 4% paraformaldehyde in autoclaved phosphate-buffered saline ŽPBS. for 5 min, rinsed twice in PBS and once in DEPC Ždiethylpyrocarbonate.-water, dehydrated and delipidated in graded series of ethanol, including 5 min incubation in chloroform, and finally rinsed twice in 100% ethanol. The sections were then air-dried. The hybridization cocktail contained 50% formamide, 4 = SSC Ž1 = SSC is 0.15 M NaCl, 0.015 sodium citrate, pH 7.0., 1 = Denhart’s Ži.e. 0.01% ficoll, 0.01% polyvinylpyrrolidone, 0.01% BSA., 1% sarcosyl, 0.02 M Sorensen’s phosphate buffer Ži.e. ¨ 0.015 M Na 2 HPO4 = 2H 2 O, 0.006 M NaH 2 PO4 = 2H 2 O., 10% dextran sulphate, 0.15 M dithiothreitol and 0.05 mgrml sheared salmon sperm DNA. For detection of PPT-A mRNA, a 48-mer oligonucleotide complementary to rat PPT-A mRNA coding for amino acids 49–64 of the tachykinin precursor protein, thus, complementary to a-, b-, g-PPT mRNA Žthe a form encodes SP exclusively, whereas the b and g forms also encode NKA. w28,41x and for detection of PPSOM mRNA, a 46-mer oligonucleotide complementary to rat PPSOM mRNA coding for amino acid 101 to 115 w20x was used. The oligonucleotides were 3X-end labeled with w a- 35 SxdATP ŽAmersham, UK. using terminal deoxyribonucleotidyl transferase ŽPromega Corporation, USA. to a specific activity of f 2 = 10 8 cpmrm g. The labelled probe was then separated from unincorporated nucleotides on a Nensorb-20 column ŽDu Pont NEN Research Products.. Hybridization was performed for 18 h in a humidified chamber at 428C. Following hybridization, the sections were rinsed 4 times 20 min in 0.1 = SSC at 458C, then rinsed in autoclaved water,

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Fig. 1. Schematic drawings of representative sections for measuring optical density in ŽA. Ž1. dorso-lateral caudate putamen, Ž2. medial caudate putamen, Ž3. nucleus accumbens core, Ž4. nucleus accumbens shell and for measuring the numerical density of hybridization-positive neurons in ŽB. medial prefrontal cortex, ŽC. nucleus accumbens and dorso-lateral caudate putamen. Open squares represent the core part, hatched squares the shell part of the nucleus accumbens and crossed-hatched squares the dorso-lateral caudate-putamen.

dehydrated in alcohol and finally air-dried. Thereafter, the slides were exposed for b-max X-ray films ŽAmersham. for 2–3 weeks and to nuclear track emulsion ŽKodak NTB2, diluted 1 : 1 with water. for 1 week ŽPPSOM

mRNA., 8 weeks ŽPPT-A mRNA.. After exposure, the films and the slides were developed with D19 ŽKodak., fixed and the slides were counter-stained with Cresyl violet before analysis.

Fig. 2. In the upper panel: high-magnification bright-field emulsion photomicrographs of preprosomatostatin mRNA-positive neurons in medial prefrontal cortex after ŽA. saline and ŽB. amperozide treatment. Scale bar s 100 m m. In the lower panel: low-magnification photomicrographs of preprotachykinin-A mRNA in section corresponding to Bregmaq 1.70 mm, after ŽC. vehicle and ŽD. haloperidol treatment.

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2.3. Neuron counting and computerized image analysis Levels of PPT-A mRNA in NAC and CP were analyzed by measuring the optical density values on the autoradiograms with a MTI CCD high resolution video camera connected to an Apple Macintosh based image analysis system ŽIMAGE v. 1.55, Wayne Rasband, NIMH, Bethesda, MD, USA.. A standard curve was obtained by having an autoradiographic 14 C microscale reference polymer ŽAmersham. exposed to the X-ray film together with the slides w38x. For each measurement, two slides were used, i.e. four sections per animal. The CP was divided into a dorso-lateral Ždl. and a medial Žm. part and the NAC was divided into a core and a shell part ŽFig. 1A. In mPFC PPT-A and PPSOM mRNAs are expressed only in a few scattered neurons. In order to more reliably measure changes in the levels of PPT-A mRNA in mPFC and levels of PPSOM mRNA in mPFC, NAC core, NAC shell and dl CP numerical density of positive neurons using a Leitz Orthoplan microscope at 200 times magnifications were counted. A positive neuron was defined as a neuron covered with ) 10 silver grains. The measured areas were in mPFC 4 mm2 ŽFig. 1B., in NAC core 2.25 mm2 , in NAC shell 1 mm2 and in dl CP 1 mm2 ŽFig. 1C..

2.4. Statistics For each set of experiments, the mean " S.E.M. of the relative changes from respective control group were calculated. Data were statistically evaluated by an one-way Žtreatment. ANOVA. A significant overall group effect was followed by Newman-Keuls multiple comparisons test. In all statistical measures, a P value of - 0.05 was considered significant. Data were statistically evaluated by using the CSS:Statistica ŽStatsoft. program.

3. Results 3.1. Effects of chronic APD treatment on PPSOM mRNA expression in the brain Compared to the respective controls, chronic treatment with haloperidol, raclopride or clozapine did not affect significantly PPSOM mRNA expression in any of the brain regions studied ŽFig. 3.. On the other hand, chronic treatment with amperozide significantly enhanced PPSOM mRNA expression selectively in the mPFC Ž52%, P 0.05. ŽFig. 2 and Fig. 3C..

Fig. 3. Relative levels of somatostatin mRNA in ŽA. nucleus accumbens ŽNAC. shell, ŽB. NAC core, ŽC. medial prefrontal cortex ŽmPFC. and ŽD. dorso-lateral caudate putamen Ždl CP. after chronic treatment with amperozide Žamp., raclopride Žrac., haloperidol Žhal. and clozapine Žclo.. Control animals for the amperozide and raclopride groups were treated with saline Žsal., whereas the controls for haloperidol and clozapine groups received vehicle Žveh.. Data were obtained by counting the numerical density of positive neurons Žsal: n s 6 in A,B,D, n s 7 in C, amp: n s 7, rac: n s 7, veh: n s 7, hal: n s 7 in A,B,D, n s 6 in C, clo: n s 8.. Data are presented as mean q S.E.M. percentage changes of control. ) P - 0.05 Žtreatment vs. control..

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Fig. 4. Relative levels of preprotachykinin-A mRNA in ŽA. nucleus accumbens ŽNAC. shell, ŽB. NAC core, ŽC. medial prefrontal cortex ŽmPFC. and ŽD. dorso-lateral Ždl. CP after chronic treatment with amperozide Žamp., raclopride Žrac., haloperidol Žhal. and clozapine Žclo.. Control animals for the amperozide and raclopride groups were treated with saline Žsal., whereas the controls for haloperidol and clozapine groups received vehicle Žveh.. In panels A,B,D, data were obtained by measuring the optical density on autoradiograms Žsal: n s 6, amp: n s 7, rac: n s 7, veh: n s 7, hal: n s 7, clo: n s 8. whereas the data in panel C were obtained by counting the numerical density of positive neurons Žsal: n s 11, amp: n s 13, rac: n s 11, veh: n s 12, hal: n s 7, clo: n s 12.. Data are presented as mean q S.E.M. percentage changes of control. ) P - 0.05, ) ) P - 0.01, ) ) ) P - 0.001 Žtreatment vs. control..

3.2. Effects of chronic ADP treatment on PPT-A mRNA expression in the brain By measuring the optical density a statistically significant decrease was seen in the shell Ž14%, P - 0.01; Fig. 4A. but not in the core subdivision of the NAC, in the dlCP Ž19%, P - 0.001; Fig. 4B., and in the mCP Ž15%, P - 0.01; data not shown., after chronic treatment with haloperidol ŽFig. 2.. In the mPFC, by measuring the numerical density of positive neurons, a statistically significant decrease Ž22%, P - 0.05; Fig. 4C. was found after chronic administration of amperozide. Chronic treatment with raclopride or clozapine did not affect significantly PPT-A mRNA expression in the studied brain regions ŽFig. 4..

4. Discussion In the present study, the technique of in situ hybridization histochemistry was adopted to obtain information on the putative involvement of somatostatin and substance P in the action of antipsychotic drugs. A statistically significant increase in the levels of PPSOM mRNA was seen in

the mPFC after amperozide treatment. Within this context, it is, indeed, striking that amperozide, a potent and relatively selective 5-HT2A receptor antagonist, also has been shown to enhance DA release w42x, 5-HT metabolism w23x and c-fos expression w43x preferentially in the mPFC compared to the striatum and the NAC. Taken together these findings indicate that amperozide exerts a selective effect on neuronal functions within the mPFC. The stimulatory action on cortical PPSOM mRNA levels is probably not due to DA-D 2 receptor blockade since amperozide has very low affinity for this receptor, and drugs with high affinity for the DA-D 2 receptor, such as haloperidol and raclopride, did not cause any significant change in PPSOM mRNA levels. In this study, we also examined the effect of clozapine, which, similarly to amperozide, exhibits a high affinity for the 5HT2A receptor. However, clozapine also has a high affinity for the 5-HT2C receptor, although it still increases DA release and c-fos expression preferentially in the mPFC w39,40,42,50,51x. In the present study, clozapine, similarly to haloperidol and raclopride, did not significantly affect PPSOM mRNA levels. Interestingly, we have recently found that amperozide and risperidone, but not clozapine, increases 5-HT release in the frontal cortex, an effect probably in part

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related to the a 2-adrenoceptor blocking action of these agents ŽHertel et al., in preparation.. In contrast, clozapine decreased 5-HT release in brain, probably due to its potent a 1-adrenoceptor antagonistic effect w19x. Thus, the difference in effect on PPSOM mRNA expression within the mPFC between amperozide and clozapine might be related to the augmenting effect of amperozide on cortical release of serotonin. Needless to say, differences in affinity for several 5-HT receptors as well as many other receptors may also be significant within this context. In contrast to the present study, in which only a tendency for a decrease in PPSOM mRNA levels was detected after treatment with haloperidol Žsee Fig. 3., a previous study found a significant decrease in the number of neurons containing PPSOM mRNA levels both in the NAC, the frontal cortex and in the medial striatum w52x after chronic haloperidol treatment. Previously, clozapine has also been shown to increase the intensity of labeling per neuron in the NAC, although not the total number of PPSOM mRNA-positive neurons; this was, however, not seen in the CP or the frontal cortex w52x. The discrepancy between the results of the present study and the previous work as regards the effect of haloperidol on PPSOM mRNA in various brain regions, may be attributed to differences in the treatment protocols, such as the duration of drug administration. Nevertheless, our results do not support the notion that APD-induced changes in the genomic expression of SOM in the rat forebrain are generally relevant to their antipsychotic effect. Rather, the findings that amperozide exhibits antidepressant-like actions in animal experiments w22x, and that the number of PPSOM mRNA-positive neurons is significantly enhanced in the prefrontal cortex following repeated electroconvulsive stimulation ŽECS. in rats w59x, might infer that an increased SOM expression is related to an antidepressant effect. This view appears somewhat supported also by clinical data showing consistently reduced levels of SOM in the cerebrospinal fluid ŽCSF. of depressed patients w8,15x, although repeated treatment with various antidepressant drugs, including those that increase serotonergic transmission has either no effect or even decreases tissue levels of SOM in various rat brain regions w25x. Since we have also found that ECS acutely or chronically administered to rats results in a decrease in extracellular concentrations of SOM in the hippocampus and the striatum w34x, an antidepressant effect might involve an altered turnover of SOM, at least in some brain regions. To this end, it remains to be determined, for example, whether antidepressant drugs consistently affect PPSOM mRNA within the mPFC. PPT-A mRNA levels were significantly affected by haloperidol and amperozide in a region selective manner. Specifically, chronic haloperidol decreased PPT-A mRNA levels in the CP and the NAC shell, whereas chronic amperozide decreased these levels in the mPFC. The present findings that haloperidol decreases PPT-A mRNA levels in the basal ganglia and that clozapine has no effect

on PPT-A mRNA expression in the CP, are in accordance with the results of previous histochemical studies w2,3,5,6,24,32x. In addition, our results are in accordance with several biochemical studies, showing decreased tachykinin tissue levels after chronic haloperidol, but not clozapine treatment w5,6,31,30,48x. In the present study, chronic administration of raclopride, which has high affinity for both DA-D 2 and DA-D 3 receptors in contrast to haloperidol, which potently binds to DA-D 2 receptors but not DA-D 3 receptors, did not affect regional brain PPT-A mRNA levels. Also, amperozide, which like clozapine shows high 5-HT2 but low DA-D 2 receptor affinity, did not affect PPT-A mRNA levels in the NAC shell and the CP. Thus, it appears that the inhibitory action of chronic haloperidol on PPT-A mRNA expression may be associated with a high level of DA-D 2 receptor occupancy. If so, the concomitant DA-D 3 receptor antagonism mediated by raclopride may, conceivably, counteract some functional consequences of its potent D 2 receptor antagonistic actions, at least at the level of tachykinin gene expression. In fact, opposing actions of D 2 and D 3 receptor antagonism, mediated by selective ligands or antipsychotics with varying degrees of D 2 relative to D 3 receptor preference, have recently been reported both in behavioral w55,58x and histochemical experiments w14x. Consequently, the results of the present study provide support for the notion that the decrease in the genomic expression and synthesis of tachykinins in the basal ganglia, if anything, may be related to side-effects rather than therapeutic effects of antipsychotic drugs Žsee above.. Thus, of the APDs studied only haloperidol, which is associated with a high prevalence of EPS in clinical experience, decreased PPT-A mRNA levels. On the other hand, clozapine and amperozide, which show very low EPS liability, as well as raclopride, which appears associated with a reduced liability for parkinsonism or dystonia Žsee Introduction., did not significantly affect PPT-A mRNA expression in the basal ganglia. Hence, studies of effects of other antipsychotic drugs andror selective D 3 receptor antagonists on tachykinin gene expression might provide additional means for pre-clinical characterization of these agents as well as prediction of their EPS liability. The present finding that amperozide, but none of the other APDs tested, significantly decreased PPT-A mRNA expression in the mPFC, is interesting in view of the fact, that amperozide differs from the other APDs, such as haloperidol and clozapine, in its selective effect on 5-HT release in the frontal cortex Žsee above.. As discussed, the selective actions of amperozide in the frontal cortex may be relevant to its putative antidepressant effect. In this regard, previous studies with antidepressant drugs have shown altered PPT mRNA levels in other brain regions, i.e. the striatum and the raphe nucleus w49,56,57x. Therefore, it would be worthwhile to study further the effect of antidepressant drugs on PPT-A mRNA expression in the mPFC.

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Acknowledgements This work was supported by grants from the Swedish Medical Research Council ŽProjects 4747 and 11026., Karolinska Institutet, Fredrik och Ingrid Thurings Stiftelse and AB Leo’s i Helsingborg Stiftelse for ¨ Forskning. We thank Astra Ltd., Sodertalje, for generous support and for ¨ ¨ providing us with raclopride, as well as Pharmacia UpJohn Ltd. and Janssen Pharmaceutica Ltd., Beerse.

References

w17x

w18x

w19x

w20x w21x

w1x Aguilar, M.A., Minarro, J., Perez-Iranzo, N. and Simon, ˜ ´ ´ V.M., Behavioral profile of raclopride in agonistic encounters between male mice, Pharmacol. Biochem. BehaÕ., 47 Ž1994. 753–756. w2x Angulo, J.A., Christoph, G.R., Manning, R.W., Burkhart, B.A. and Davis, L.G., Reduction of dopamine receptor activity differentially alters striatal neuropeptide mRNA levels, AdÕ. Exp. Med. Biol., 221 Ž1987. 385–391. w3x Angulo, J.A., Cadet, J.L. and McEwen, B.S., Effect of typical and atypical neuroleptic treatment on protachykinin mRNA levels in the striatum of the rat, Neurosci. Lett., 113 Ž1990. 217–221. w4x Axelsson, R., Nilsson, A., Christensson, E. and Bjork, ¨ A., Effects of amperozide in schizophrenia, Psychopharmacology, 104 Ž1991. 287–292. w5x Bannon, M.J., Lee, J.-M., Giraud, P., Young, A., Affolfer, H.-U. and Bonner, T.I., Dopamine antagonist haloperidol decreases substance P, substance K, and preprotachykinin mRNAs in rat striatonigral neurons, J. Biol. Chem., 261 Ž1986. 6640–6642. w6x Bannon, M.J., Elliott, P.J. and Bunney, E.B., Striatal tachykinin biosynthesis: regulation of mRNA and peptide levels by dopamine agonists and antagonists, Mol. Brain Res., 3 Ž1987. 31–37. w7x Beal, M.F. and Martin, J.B., Effects of neuroleptic drugs on brain somatostatin-like-immunoreactivity, Neurosci. Lett., 47 Ž1984. 125– 130. w8x Bissette, G. and Myers, B., Minireview: somatostatin in Alzheimer’s disease and depression, Life Sci., 51 Ž1992. 1389–1410. w9x Bjork, ¨ A., Bergman, I. and Gustavsson, G., Amperozide in the treatment of schizophrenic patients. A preliminary report. In H.Y. Meltzer ŽEd.., NoÕel Antipsychotic Drugs, Raven, New York, 1992, pp. 47–57. w10x Conley, R.R., Schulz, S.C., Baker, R.W., Collins, J.F. and Bell, J.A., Clozapine efficacy in schizophrenic nonresponders, Psychopharmacol. Bull., 24 Ž1988. 269–274. w11x Coward, D.M., General pharmacology of clozapine, Br. J. Psychiatry, 160 ŽSuppl. 17. Ž1992., 5–11. w12x Deutch, A.Y., Prefrontal cortical dopamine systems and the elaboration of functional corticostriatal circuits: implications for schizophrenia and Parkinsson’s disease, J. Neural Transm. – Gen. Sect., 91 Ž1993. 197–221. w13x Deutch, A.Y. and Cameron, D.S., Pharmacological characterization of dopamine system in the nucleus accumbens core and shell, Neuroscience, 46, Ž1992. 49–56. w14x Diaz, J., Levesque, D., Griffon, N., Lammers, C.H., Martres, M.-P., ´ Sokoloff, P. and Schwartz, J.-C., Short communication: opposing roles for dopamine D 2 and D 3 receptors on neurotensin mRNA expression in nucleus accumbens, Eur. J. Neurosci., 6 Ž1994. 1384– 1387. w15x Epelbaum, J., Somatostatin in the central nervous system: physiology and pathological modifications, Prog. Neurobiol., 27 Ž1986. 63–100. w16x Farde, L., Wiesel, F.-A., Jansson, P., Uppfeldt, G., Wahlen, A. and Sedvall, G., An open label trial of raclopride in acute schizophrenia.

w22x w23x

w24x

w25x

w26x

w27x

w28x

w29x

w30x

w31x

w32x

w33x

w34x

w35x

w36x

281

Confirmation of D 2-dopamine receptor occupancy by PET, Psychopharmacology, 94 Ž1988. 1–7. Farde, L., Nordstrom, ¨ A.L., Wiesel, F.-A., Pauli, S., Halldin, C. and Sedvall, G., Positron emission tomographic analysis of central D1 and D 2 dopamine receptor occupancy in patients treated with classical neuroleptics and clozapine, Arch. Gen. Psychiatry, 49 Ž1992. 538–544. Farde, L., Nordstrom, ¨ A.L., Nyberg, S., Halldin, C. and Sedvall, G., D1 -, D 2 -, and 5HT2-receptor occupancy in clozapine-treated patients, J. Clin. Psychiatry, 55 ŽSuppl. B. Ž1994. 67–69. Ferre, ´ S. and Artigas, F., Clozapine decreases serotonin extracellular levels in the nucleus acumbens by a dopamine receptor-independent mechanism, Neurosci. Lett., 187 Ž1995. 61–64. Goodman, R.H., Aron, D.C. and Roos, B.A., Rat pre-prosomatostatin, J. Biol. Chem., 258 Ž1983. 5570–5573. Gustafsson, B. and Christensson, E., Amperozide – a new putatively antipsychotic drug with a limbic mode of action on dopamine mediated behaviour, Pharmacol. Toxicol. ŽSuppl. 1. Ž1990. 12–17. Gustafsson, B. and Christensson, E., Amperozide and emotional behaviour, Pharmacol. Toxicol., ŽSuppl. 1. Ž1990. 34–39. Hertel, P., Nomikos, G.G., Iurlo, M. and Svensson, T.H., Risperidone: regional effects in vivo on release and metabolism of dopamine and serotonin in the rat brain., Psychopharmacology, 124 Ž1996. 74–86. Humpel, C., Knaus, G.A., Auer, B., Knaus, H.-G., Haring, C., Theodorsson, E. and Saria, A., Effects of haloperidol and clozapine on preprotachykinin-A messenger RNA, tachykinin tissue levels, release and neurokinin–1 receptors in the striato-nigral system, Synapse, 6 Ž1990. 1–9. Kakigi, T., Maeda, K., Kaneda, H. and Chihara, K., Repeated administration of antidepressant drugs reduces regional somatostatin concentrations in rat brain, J. Affect. Disorders, 25 Ž1992. 215–220. Kane, J., Honigfeld, G., Singer, J., Meltzer, H. and the Clozaril Collaborative Study Group, Clozapine for the treatment-resistant schizophrenic, Arch. Gen. Psychiatry, 45 Ž1988. 789–796. ¨ Kohler, C., Hall, H., Ogren, S.-O. and Gawell, L., Specific in vitro ¨ and in vivo binding of 3 H-raclopride. Biochem. Pharmacol., 34 Ž1985. 2251–2259. Krause, J.E., Chirgwin, J.M., Carter, M.S., Xu, Z.S. and Hershey, A.D., Three rat preprotachykinin mRNAs encode the neuropeptides substance P and neurokinin A, Proc. Natl. Acad. Sci. USA, 84 Ž1987. 881–885. Leysen, J.E. and Niemegeers, C.J.E., Neuroleptics. In A. Lajtha ŽEd.., Handbook in Neurochemistry, Vol. 9, Plenum, New York, 1985, pp. 331–361. Li, S.J., Sivam, S.P., McGinty, J.F., Huang, Y.S. and Hong, J.S., Dopaminergic regulation of tachykinin metabolism in the striatonigral pathways., J. Pharmacol. Exp. Ther., 243 Ž1987. 792–798. Lindefors, N., Brodin, E. and Ungerstedt, U., Neuroleptic treatment induces region-specific changes in levels of neurokinin A and substance P in rat brain, Neuropeptides, 7 Ž1986. 265–280. Lindefors, N., Amphetamine and haloperidol modulate preprotachykinin A mRNA expression in rat nucleus accumbens and caudate-putamen, Mol. Brain Res., 13 Ž1992. 151–154. Marcus, M.M., Nomikos, G.G. and Svensson, T.H., Differential actions of typical and atypical antipsychotic drugs on dopamine release in the core and shell of the nucleus accumbens, Eur. Neuropsychopharmacol., 6 Ž1996. 29–38. Mathe, ´ A.A., Nomikos, G.G. and Svensson, T.H., Effects of acute and chronic electroconvulsive treatment on interstitial concentrations of somatostatin in the rat hippocampus and striatum, Prog. NeuroPsychopharmacol. Biol. Psychiatry, 19 Ž1995. 323–332. McCreadie, R.G. and The British Isles Raclopride Study Group, A double-blind comparison of raclopride and haloperidol in the acute phase of schizophrenia, Acta Psychiatry Scand., 86 Ž1992. 391–398. Meltzer, H.Y., Matsubara, S. and Lee, J.C., Classification of typical and atypical antipsychotic drugs on the basis of dopamine D-1, D-2

282

w37x w38x

w39x

w40x

w41x

w42x

w43x

w44x

w45x

w46x

w47x w48x

M.M. Marcus et al.r Molecular Brain Research 45 (1997) 275–282 and serotonin 2 p K i values, J. Pharmacol. Exp. Ther., 251 Ž1989. 238–246. Meltzer, H.Y. and Nash, J.F., VII. Effects of antipsychotic drugs on serotonin receptors, Pharmacol. ReÕ., 43 Ž1991. 587–604. Miller, J.A., The calibration of 35 S or 32 P with 14 C-labeled brain paste or 14 C-plastic standards for quantitative autoradiography using LKB Ultrofilm or Amersham Hyperfilm, Neurosci. Lett., 121 Ž1991. 211–214. Moghaddam, B. and Bunney, B.S., Acute effects of typical and atypical antipsychotic drugs on the release of dopamine from prefrontal cortex, nucleus accumbens, and striatum of the rat: an in vivo microdialysis study, J. Neurochem., 54 Ž1990. 1755–1760. Moghaddam, B. and Bunney, B.S., Utilization of microdialysis for assessing the release of mesotelencephalic dopamine following clozapine and other antipsychotic drugs, Prog. Neuro-Psychopharmacol. Biol. Psychiat., 14 Ž1990. S51–S57. Nawa, H., Kotani, H. and Nakanishi, S., Tissue-specific generation of two preprotachykinin mRNAs from one gene by alternative RNA splicing, Nature, 312 Ž1984. 729-734. Nomikos, G.G., Iurlo, M. Andersson, J.L., Kimura, K. and Svensson, T.H., Systemic administration of amperozide, a new atypical antipsychotic drug, preferentially increases dopamine release in the rat medial prefrontal cortex, Psychopharmacology, 115 Ž1994. 147– 156. Nomikos, G.G., Tham, C.-S., Fibiger, H.C. and Svensson, T.H., The putative antipsychotic drug amperozide preferentially increases c-fos expression in the rat medial prefrontal cortex and the lateral septum, Neuropsychopharmacology, Ž1996. submitted. Nordstrom, ¨ A.-L., Farde, L. and Halldin, C., Time course of D 2dopamine receptor occupancy examined by PET after single oral doses of haloperidol, Psychopharmacology, 106 Ž1992. 433–438. Nordstrom, ¨ A.-L., Farde, L. and Halldin, C., High 5-HT2 receptor occupancy in clozapine treated patients demonstrated by PET, Psychopharmacology, 110 Ž1993. 365–367. ¨ Ogren, S.O., Hall, H., Kohler, C., Magnusson, O. and Sjostrand, ¨ ¨ S.E., The selective dopamine D 2 receptor antagonist raclopride discriminates between dopamine-mediated motor functions, Psychopharmacology, 90 Ž1986. 287–294. Paxinos, G. and Watson, C., The Rat Brain in Stereotaxic Coordinates, 2nd edn., Academic Press, Sydney, Australia, 1986. Radke, J.M., MacLennan, A.J., Vincent, S.R. and Fibiger, H.C.,

w49x

w50x

w51x

w52x

w53x w54x w55x

w56x

w57x

w58x

w59x

Comparison between short- and long-term haloperidol administration on somatostatin and substance P concentrations in the rat brain, Brain Res., 445 Ž1988. 55–60. Riley, L.A., Jonakait, G.M. and Hart, R.P., Serotonin modulates the levels of mRNAS coding for thyrotropin-releasing hormone and preprotachykinin by different mechanisms in medullary raphe neurons, Mol. Brain Res., 17 Ž1993. 251–257. Robertson, G.S. and Fibiger, H.C., Neuroleptics increase c-fos expression in the forebrain: contrasting effects of haloperidol and clozapine, Neuroscience, 46 Ž2. Ž1992. 315–328. Robertson, G.S., Matsumura, H. and Fibiger, H.C., Induction patterns of Fos-like immunoreactivity in the forebrain as predictors of atypical antipsychotic activity, J. Pharmacol. Exp. Ther., 271 Ž1994. 1058–1066. Salin, P., Mercugliano, M. and Chesselet, M.F., Differential effects of chronic treatment with haloperidol and clozapine on the level of preprosomatostatin mRNA in the striatum, nucleus accumbens, and frontal cortex of the rat, Cell. Mol. Neurobiol., 10 Ž1990. 127–144. Seeman, P., Brain dopamine receptors, Pharmacol. ReÕ., 32 Ž1980. 229–313. Svartengren, J. and Simonsson, P., Receptor binding properties of amperozide, Pharmacol. Toxicol. ŽSuppl. 1. Ž1990. 8–11. Svensson, K., Carlsson, A., Huff, R.M., Kling-Petersen, T. and Waters, N., Behavioral and neurochemical data suggest functional differences between dopamine D 2 and D 3 receptors, Eur. J. Pharmacol., 263 Ž1994. 235–243. Walker, P.D., Riley, L.A., Hart, R.P. and Jonakait, G.M., Serotonin regulation of tachykinin biosynthesis in the rat neostriatum, Brain Res., 546 Ž1991. 33–39. Walker, P.D., Riley, L.A., Hart, R.P. and Jonakait, G.M., Serotonin regulation of neostriatal tachykinins following neonatal 6-hydroxydopamine lesions, Brain Res., 557 Ž1991. 31–36. Waters, N., Svensson, K., Haadsma-Svensson, S.R., Smith, M.W. and Carlsson, A., The dopamine D 3-receptor: a postsynaptic receptor inhibitory on rat locomotor activity, J. Neural Transm. – Gen. Sect., 94 Ž1993. 11–19. Zachrisson, O., Mathe, ´ A.A., Stenfors, C. and Lindefors, N., Limbic effects of repeated electroconvulsive stimulation on neuropeptide Y and somatostatin mRNA expression in the rat brain, Mol. Brain Res., 31 Ž1995. 71–85.