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Increases in cortical neuropeptide Y and somatostatin concentrations following haloperidol-depot treatment in rats
Neuropeptides (1995) 29, 157-161 © Pearson Professional Ltd 1995
Increases in Cortical Neuropeptide Y and Somatostatin Concentrations Following Haloperidoldepot Treatment in Rats K. SAKAI*, K. MAEDA$, K. CHIHARAt and H. KANEDA*
*Departments of Psychiatry and ?Medicine, Kobe University School of Medicine, Kobe 650, and ¢Hyogo Institute for Aging Brain and Cognitive Disorders, 520 Saisho-koh, Himeji 670, Japan (Reprint requests to KM)
Abstract--The concentrations of neuropeptide Y (NPY) and somatostatin (SS) have been said to be altered in the brain and cerebrospinal fluid of schizophrenic patients. This alteration could result from the neuroleptic treatment. Therefore, it is of interest to evaluate effects of long-term treatment with neuroleptics on the peptide concentrations in the brain. Haloperidol (HPD) is one of the most frequently used neuroleptics for the treatment of schizophrenia. We determined regional brain levels of NPY and SS following HPD administration in the rat. A single intraperitoneal injection of HPD, at a dose of 1 mg/kg, did not affect peptide levels in the brain regions studied. Four weeks after an intramuscular deposit injection of HPD decanoate, 50 mg/kg, NPY concentrations were increased in a number of areas of the cerebral cortex. SS content was also significantly increased in the lateral prefrontal cortex and anterior cingulate cortex. Both peptide levels were decreased in the striatum. These results suggest that the reduction found in these peptides' levels in the cerebral cortex of the brain from schizophrenic patients may not be the consequence of HPD treatment and that these peptides' levels might be increased in the cerebral cortex of the brain of schizophrenic patients following the treatment with HPD.
Introduction Neuropeptide Y (NPY) is one of the most widely distributed peptides in the human brain. A large number of physiological and pharmacological
Date received 21 February 1995 Date accepted 2 March 1995 Correspondence to K. Maeda, Hyogo Institute for Aging Brain and Cognitive Disorders, 520 Saisho-koh, Himeji 670, Japan.
actions of NPY have been suggested. 1 Recent clinical data also suggest the involvement of NPY in schizophrenia. Altered concentrations of NPY in the discrete regions of the brain 2 and in cerebrospinal fluid 3 have been demonstrated in schizophrenic patients. Somatostatin (SS) was originally isolated from the hypothalamus and thereafter found to be distributed widely in the brain. NPY and SS are co-localized in and co-released from neurons in the human and rat cortex. 4 Nemeroff
157
158 et al 5 have found reduced concentrations of SS in discrete areas of schizophrenic brains. Bissette et al 6 have reported that SS is reduced in CSF from patients with schizophrenia. These findings, however, may be secondary to long-term treatment with neuroleptics. Haloperidol (HPD) is a D2 receptor antagonist and one of the most frequently prescribed neuroleptic drugs for treatment of schizophrenia. It is of interest to evaluate effects of HPD on brain NPY and SS concentrations. There have been some studies on effects of HPD on brain NPY or SS in experimental animals. However, in most of these studies, HPD was administered by acute, intraperitoneal (ip) injections. In order to achieve a therapeutic effect with HPD, a one- to two-week treatment period is required in humans. The pharmacokinetics of ip injections, which produce a rapid increase and rapid decrease in drug concentration in the brain, differs from that seen in clinical use following oral administration or intramuscular (im) injection. A daily ip injection may be stressful and could affect peptide concentrations in the brain. In the present study, we determined effects of depot HPD decanoate (HPDDD) on brain NPY and SS content in rats.
Materials and methods
Male Wistar rats (390420 g b.w.) were maintained in a light- and temperature- controlled room. In the acute experiment, animals received 1 mg/ml/kg of HPD (Serenace P', Dainippon Pharm. Co., Japan) or the same amount of physiologic saline intraperitoneally and were sacrificed by decapitation 4 h after the injection. In the chronic study HPD-DD (HalomanthR, Dainippon Pharm. Co., Japan), at a dosage of 50 mg/kg of HPD, was injected into the femoral muscle of the rat (n = 8). The control rats (n = 7) received sesame oil injections. After 4 weeks the rats were sacrificed by decapitation. The brain was then sliced into 2 mm sections and dissected according to Palcovits' method 7,s into the following 12 regions: medial prefrontal cortex (mPFC), lateral prefrontal cortex (IPFC), anterior cingulate cortex (aCg), posterior cingulate cortex (pCg), motor areas of the frontal cortex (FC), temporal cortex (TC), parietal cortex (PC), occipital cortex (OC), striatum (St), hippocampus (Hp),
NEUROPEPTIDES amygdala (Am), and hypothalamus (Ht). Tissues containing NPY-like immunoreactivities (LI) and SS-LI were extracted into ice cold 2 N acetic acid, and the peptides were measured by specific radioimmunoassays (RIAs), as reported previous. 9 Briefly, in the NPY RIA, a polyclonal NPY antiserum that recognizes the N-terminal portion of the NPY molecule and does not cross-react with rat pancreatic polypeptide or rat peptide YY was used. The sensitivity of the assay was 0.4 pg/0.1 ml. In the SS RIA, we used an antiserum to SS that recognized the mid portion of the molecule. No crossreactivity was shown with any of the hypothalamic peptides. The minimal detectable concentration was 1.0 pg/0.1 ml. The differences between the sample means were determined by the non-paired Student's t-test.
Results
An acute ip injection of HPD did not alter the concentrations of the peptides in any region (Table). As shown in Figure 1, an im injection of HPD-DD tended to elevate NPY-LI levels in all the regions except the striatum and hippocampus. NPY-LI levels were significantlyhigher in a number of cortical regions, e.g. motor areas of the frontal cortex, anterior cingulate cortex, frontal cortex, temporal cortex and occipital cortex, compared with those in the control. NPY-LI, however, was reduced in the striatum. SS-LI also tended to be high in the cortical regions after HPD-DD treatment, but significant increases were only found in the lateral prefrontal cortex and anterior cingulate cortex. SS-LI in the striatum was significantly lower than that of the control (Fig. 2).
Discussion
We found an elevation in the NPY content of the cerebral cortex, and a reduction in the striatum following HPD-DD administration. The dosage, 50 mg/kg of HPD-DD, is equivalent to a daily oral dose of 2.5 mg/kg of HPD. 1° Smialowska and Legutko 11have found an increase in NPY levels in the locus coeruleus but not in the striatum after injecting HPD every 6 h (2.5 mg/kg, ip) for 24 h in rats. The cortical content of the peptide was not
INCREASE
IN CORTICAL
NPY AND SOMATOSTATIN
159
BY HALOPERIDOL
Table Effect of acute injection of h a l o p e r i d o l o n regional b r a i n n e u r o p e p t i d e Y - a n d somatostatin-like i m m u n o r e a c t i v i t y levels
Reyions
Neuropeptide Y Control Haloperidol
Medial prefrontal cortex Lateral prefrontal cortex Anterior cingulate cortex Posterior cingulate cortex Motor areas of frontal cortex Temporal cortex Parietal cortex Occipital cortex Striatum Hippocampus Amygdala Hypothalamus
0.148___0.023 0.159±0.021 . . 0.116±0.004 0,138±0.015 . 0,175±0.010 0,086 ± 0.002 0.128 ±0.002 0.200 ± 0.043 0.631+_0.040
Somatostatin Control Haloperidol
0.171 ±0.021 1.252±0.126 0.181+__0.023 0.664+0.073 . . . . . . 0.131 ±0.004 1.010±0.040 0.168±0.012 0.978-t-0.164 . . . 0.206±0.012 1.443±0.129 0.088 ± 0.007 0.770 ± 0.100 0.109_+0.005 1.350_+0.050 0.254±0.043 2.620 ± 0.323 0.757___0.050 2.453±0.435
1.505+0.071 0.711 ±0.059 1.160±0.040 1.284-1-0.096 1.642±0.170 0.690 ± 0,050 1.230 ±0.070 2.310+0.155 2.384±0.192
Neuropeptide Y- and somatostatin-like immunoreactivity levels are expressed as pg//~g protein. (Mean_+ SEM). Six animals were used in each experiment, Haloperidol, 1 mg/kg, was administered intraperitoneally 4 b before sacrifice.
1.0.
0.9 ¸
1"3 control II
HPD
0.8,
0.7 ¸
=
0.6
e
o. 0.5
3 ..i
z
11.4
0.3 ¸
.d
**
~h
--r
2
0.2'
0.1 ¸
0.0 mPFC IPFC aCg pCg
FC
TC
PC
OC
St
Hp
Am
Ht
Fig. 1 Regional brain neuropeptide Y-like immunoreactivities (NPY-LI) following haloperidol decanoate depot (HPD, 50 mg/kg) in rats. Abbreviations used are as follows: mPFC; medial prefrontal cortex, IPFC; lateral prefrontal cortex, aCg; anterior cingulate cortex, pCg; posterior cingulate cortex, FC; motor areas of the frontal cortex, TC; temporal cortex, PC; parietal cortex, OC; occipital cortex, St; striatum, Hp; hippocampus, Am; amygdala, and Ht; hypothalamus. The vertical bars are m e a n ± SEM. *: P < 0.05 and **: P < 0.01.
0
mPFCIPFC aCg pCg
FC
TC
PC
OC
St
Hp
Am
Ht
Fig. 2 Regional brain somatostatin-like immunoreactivities (SS-LI) following haloperidol decanoate depot (HPD, 50 mg/kg) in rats. Abbreviations used are the same as in Figure 1. The vertical bars are mean+_SEM. *: P < 0.05 and **: P < 0.01.
160 determined in their study. Long-term treatment with H P D has been reported to increase NPY staining in the arcuate nucleus. 12 Our results are partly consistent with observations by Miyake et al. 13 They found that the content of NPY is decreased in the caudate-putamen, but increased in lateral prefrontal cortex, and does not change in the other cortical areas examined after repeated ip injections of 5 mg/kg of H P D for 21 days. The differences between our results are a matter of speculation. The route of administration of H P D was different in the two studies however. Stress associated with daily ip injection, may have affected cortical NPY content in their study. Psychological stress has been demonstrated to reduce CSF NPY concentrations in man. 14 An ip injection produces a rapid increase and a rapid decrease in drug concentrations in the circulation and probably in the brain. Plasma H P D levels are remarkably stable following H P D - D D , compared with those during oral or ip administration of the drug.l° Therefore, the different pharmacodynamics due to the different administration route and/or the different formula of the drugs might be responsible for the difference in the results. In the present study, NPY levels in the cortex, including the temporal cortex, were increased after the administration of H P D - D D . Frederiksen et al 2 have shown reduced concentrations of NPY in the temporal cortex but not in the hypothalamus of the brains from schizophrenic patients, although normal tissue concentrations of NPY have also been reported in postmortem amygdala.~5 The temporal lobe seems to be a candidate site for schizophrenia since positron emission tomography studies have shown a lower metabolic rate in the temporal lobe, as well as the frontal lobe. 16 However, N P Y levels in CSF of drug-free chronic schizophrenics were reported to be higher than in controls? Normal N P Y but reduced peptide YY concentrations in CSF were observed in drug-free schizophrenic patients, iv Berrettini et a118 have observed no differences in CSF NPY levels between normal volunteers and 2-week drug-free chronic schizophrenics. No significant differences were found after treating schizophrenic patients for 4 weeks with fluphenazine either. These findings suggest that if N P Y is involved in the pathogenesis of schizophrenia, an abnormality is not detectable in the CSF. In the present study we found that acutely
NEUROPEPTIDES injected H P D was without effect on NPY or SS concentrations in rats. In general, 2 or more weeks are necessary to obtain the therapeutic effect of H P D in the treatment of schizophrenia. Thus, the treatment with H P D of schizophrenic patients could elevate or normalize reduced NPY levels in the cerebral cortex of the brain. In the present study, the effect of H P D - D D on N P Y concentrations in the striatum was different from that in the cortex. Striatal NPY content was reduced and cortical NPY was elevated following treatment with HPD. The effects of dopaminergic transmission on NPY levels seem to be region-specific. We have shown a statistically-significant reduction in striatal N P Y concentrations following 6-hydroxydopamine, a dopamine neurotoxin, or sulpiride, a selective D2 antagonist. 19 An opposite role of D2 receptors in the striatum from that in the cortex is suggested in the regulation by dopamine of N P Y metabolism? ° SS concentrations were also decreased in the striatum following H P D - D D administration in the present study. Beal and Martin 2I administered H P D at a dose of 2.5 mg/kg, ip for 3 weeks to rats and observed a reduction of SS levels in the striatum. This finding is replicated by Radke et a122who have demonstrated a reduction in SS concentrations in the caudate-putamen and nucleus accumbens in the rats given with H P D for 3 weeks in the drinking water. We found an increase in SS content in a limited number of cortical areas in this study. Beal and Martin 21 found an insignificant reduction of SS levels by H P D in prefrontal cortex, and they examined no other cortical areas. Radke et a122 found that SS content in the cortex was unaltered after 3 weeks or 8 months of H P D treatment. There has been no other report describing HPD-induced changes in SS context in the cortex. The effect of H P D on cortical SS seems to be limited, compared to NPY. Reduced concentrations of SS have been found in discrete areas of schizophrenic brains. 5 Bissette et al 6 have reported that SS is reduced in CSF from patients with schizophrenia. Reduced SS levels could also be increased in the cerebral cortex of the brains of schizophrenic patients following treatment with HPD. References 1. Heilig, M. and Widerl6v, E. Neuropeptide Y: an overview
INCREASE IN CORTICAL NPY AND SOMATOSTATIN BY HALOPERIDOL
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4.
5. 6.
7. 8. 9.
10.
11. 12.
of central distribution, functional aspects, and possible involvement in neuropsychiatric illness. Acta Psychiatr. Scand. 1990; 82: 95-114. Frederiksen, S. O., Ekman, R., Gottfries, C. G., Widerlov, E. and Jonsson, S. Reduced concentrations of galanin, arginine vasopressin, neuropeptide Y and peptide YY in the temporal cortex but not in the hypothalamus of brains from schizophrenics. Acta Psychiatr. Scand. 1991; 83:273 277. Peters, J., Van Kammen, D. P., Gelernter, J., Yao, J. and Shaw, D. Neuropeptide Y-like immunoreactivity in schizophrenia, relationships with clinical measures. Schizophrenia Res. 1990; 3: 287-294. Vincent, S. R., Skirball, L., H6kfelt, T. et al. Coexistence of somatostatin- and avian pancreatic polypeptide (APP)-like immunoreactivity in some forebrain neurons. Neuroscience 1982; 7: 439-466. Nemeroff, C. B. and Bissette, G. Neuropeptides, dopamine, and schizophrenia. Ann. NY Acad. Sci. 1988; 537:273 291. Bissette, G., Widerl6v, E., Walleu H. Alterations in cerebrospinal fluid concentrations of somatostatin-like immunoreactivity in neuropsychiatric disorders. Arch. Gen. Psychiatry 1986; 43:1148-1151. Palkovits, M. and Brownstein, M. J. Maps and guide to microdissection of the rat brain. New York: Elsevier, 1988. Kaneda, H. and Maeda, K. Alteration in regional brain neuropeptides following intracerebroventricular infusion of excitotoxins in rats. Biol. Psychiatry 1994; 36:103 109. Maeda, K., Yasuda, M., Kanada, H., Maeda, S. and Yamadori, A. Cerebrospinal fluid (CSF) neuropeptide Y- and somatostatin-like immunoreactivities in man. Neuropeptides 1994; 27: 323-332. Deberdt, R., Elens, P., Berghmans, W. et al. Intramuscular haloperidol decanoate for neuroleptic maintenance therapy: Efficacy, dosage schedule and plasma levels, an open multicenter study. Acta Psychiatr. Scand. 1980; 62: 356-363. Smialowska, M. and Legutko, B. HaloperidoMnduced increase in neuropeptide Y immunoreactivity in the locus coeruleus of the rat brain. Neuroscience. 1992; 47: 351-355. Li, S. and Pelletier, G. The role of dopamine in the control of neuropeptide Y neurons in the rat arcuate nucleus. Neurosci. Lett. 1986; 69: 74-77.
161
13. Miyake, M., Iguchi, K., Okamura, H. et al. Effect of haloperidol on immunoreactive neuropeptide Y in rat cerebral cortex and basal ganglia. Brain Res. Bull. 1990; 25: 263269. 14. Widerl6v, E., Heilig, M., Ekman, R. and Wahlestedt, C. Neuropeptide Y - possible involvement in depression and anxiety. In: Mutt, V., Fuxe, K., Hokfelt, T., Lundberg, J. M. (eds), Nobel Conference on NPY. New York: Raven Press, 1989: 331-342. 15. Beal, F. M., Svendsen, C. N., Bird, E. D. and Martin, J. B. Somatostatin and neuropeptide Y are altered in the amygdala in schizophrenia. Neurochem. Pathol. 1987; 6: 169176. 16. Buchsbaum, M. S. The frontal lobes, basal ganglia, and temporal lobes as sites for schizophrenia. Schizophr. Bull. 1990; 16: 379-389. 17. WiderlSv, E., Lindstr6m, L. H., Wahlestedt, C. and Ekman, R. Neuropeptide Y and peptide YY as possible cerebrospinal fluid markers for major depression and schizophrenia, respectively. J. Psychiat. Res. 1988; 22: 69-79. 18. Berrettini, W. H., Doran, A. R., Kelsoe, J., Roy, A. and Pickar, D. Cerebrospinal fluid neuropeptide Y in depression and schizophrenia. Neuropsychopharmacology 1987; 1:8183. 19. Maeda, K., Kawata, E., Sakai, K. and Chihara, K. Effects of putative cognitive function-enhancing drugs and dopaminergic agents on somatostatin and neuropeptide Y in rat brain. Eur, J. Pharmacol. 1993; 233: 227-235. 20. Engber, T. M., Boldry, R. C., Kuo, S. and Chase, T. N. Dopaminergic modulation of striatal neuropeptides: differential effects of D1 and D2 receptor stimulation on somatostatin, neuropeptide Y, neurotensin, dynorphin and enkephalin. Brain Res. 1992; 581: 261-272. 21. Beal, F. M. and Martin, J. B. Effects ofneuroleptic drugs on brain somatostatin-like immunoreactivity. Neurosci. Lett. 1984; 47: 125-130. 22. Radke, J. M., MacLennan, A. J., Vincent, S. R. and Fibiger, H. C. Comparison between short- and long-term haloperidol administration on somatostatin and substance P concentrations in the rat brain. Brain Res. 1988; 445: 55~50.
Increases in Cortical Neuropeptide Y and Somatostatin Concentrations Following Haloperidoldepot Treatment in Rats K. SAKAI*, K. MAEDA$, K. CHIHARAt and H. KANEDA*
*Departments of Psychiatry and ?Medicine, Kobe University School of Medicine, Kobe 650, and ¢Hyogo Institute for Aging Brain and Cognitive Disorders, 520 Saisho-koh, Himeji 670, Japan (Reprint requests to KM)
Abstract--The concentrations of neuropeptide Y (NPY) and somatostatin (SS) have been said to be altered in the brain and cerebrospinal fluid of schizophrenic patients. This alteration could result from the neuroleptic treatment. Therefore, it is of interest to evaluate effects of long-term treatment with neuroleptics on the peptide concentrations in the brain. Haloperidol (HPD) is one of the most frequently used neuroleptics for the treatment of schizophrenia. We determined regional brain levels of NPY and SS following HPD administration in the rat. A single intraperitoneal injection of HPD, at a dose of 1 mg/kg, did not affect peptide levels in the brain regions studied. Four weeks after an intramuscular deposit injection of HPD decanoate, 50 mg/kg, NPY concentrations were increased in a number of areas of the cerebral cortex. SS content was also significantly increased in the lateral prefrontal cortex and anterior cingulate cortex. Both peptide levels were decreased in the striatum. These results suggest that the reduction found in these peptides' levels in the cerebral cortex of the brain from schizophrenic patients may not be the consequence of HPD treatment and that these peptides' levels might be increased in the cerebral cortex of the brain of schizophrenic patients following the treatment with HPD.
Introduction Neuropeptide Y (NPY) is one of the most widely distributed peptides in the human brain. A large number of physiological and pharmacological
Date received 21 February 1995 Date accepted 2 March 1995 Correspondence to K. Maeda, Hyogo Institute for Aging Brain and Cognitive Disorders, 520 Saisho-koh, Himeji 670, Japan.
actions of NPY have been suggested. 1 Recent clinical data also suggest the involvement of NPY in schizophrenia. Altered concentrations of NPY in the discrete regions of the brain 2 and in cerebrospinal fluid 3 have been demonstrated in schizophrenic patients. Somatostatin (SS) was originally isolated from the hypothalamus and thereafter found to be distributed widely in the brain. NPY and SS are co-localized in and co-released from neurons in the human and rat cortex. 4 Nemeroff
157
158 et al 5 have found reduced concentrations of SS in discrete areas of schizophrenic brains. Bissette et al 6 have reported that SS is reduced in CSF from patients with schizophrenia. These findings, however, may be secondary to long-term treatment with neuroleptics. Haloperidol (HPD) is a D2 receptor antagonist and one of the most frequently prescribed neuroleptic drugs for treatment of schizophrenia. It is of interest to evaluate effects of HPD on brain NPY and SS concentrations. There have been some studies on effects of HPD on brain NPY or SS in experimental animals. However, in most of these studies, HPD was administered by acute, intraperitoneal (ip) injections. In order to achieve a therapeutic effect with HPD, a one- to two-week treatment period is required in humans. The pharmacokinetics of ip injections, which produce a rapid increase and rapid decrease in drug concentration in the brain, differs from that seen in clinical use following oral administration or intramuscular (im) injection. A daily ip injection may be stressful and could affect peptide concentrations in the brain. In the present study, we determined effects of depot HPD decanoate (HPDDD) on brain NPY and SS content in rats.
Materials and methods
Male Wistar rats (390420 g b.w.) were maintained in a light- and temperature- controlled room. In the acute experiment, animals received 1 mg/ml/kg of HPD (Serenace P', Dainippon Pharm. Co., Japan) or the same amount of physiologic saline intraperitoneally and were sacrificed by decapitation 4 h after the injection. In the chronic study HPD-DD (HalomanthR, Dainippon Pharm. Co., Japan), at a dosage of 50 mg/kg of HPD, was injected into the femoral muscle of the rat (n = 8). The control rats (n = 7) received sesame oil injections. After 4 weeks the rats were sacrificed by decapitation. The brain was then sliced into 2 mm sections and dissected according to Palcovits' method 7,s into the following 12 regions: medial prefrontal cortex (mPFC), lateral prefrontal cortex (IPFC), anterior cingulate cortex (aCg), posterior cingulate cortex (pCg), motor areas of the frontal cortex (FC), temporal cortex (TC), parietal cortex (PC), occipital cortex (OC), striatum (St), hippocampus (Hp),
NEUROPEPTIDES amygdala (Am), and hypothalamus (Ht). Tissues containing NPY-like immunoreactivities (LI) and SS-LI were extracted into ice cold 2 N acetic acid, and the peptides were measured by specific radioimmunoassays (RIAs), as reported previous. 9 Briefly, in the NPY RIA, a polyclonal NPY antiserum that recognizes the N-terminal portion of the NPY molecule and does not cross-react with rat pancreatic polypeptide or rat peptide YY was used. The sensitivity of the assay was 0.4 pg/0.1 ml. In the SS RIA, we used an antiserum to SS that recognized the mid portion of the molecule. No crossreactivity was shown with any of the hypothalamic peptides. The minimal detectable concentration was 1.0 pg/0.1 ml. The differences between the sample means were determined by the non-paired Student's t-test.
Results
An acute ip injection of HPD did not alter the concentrations of the peptides in any region (Table). As shown in Figure 1, an im injection of HPD-DD tended to elevate NPY-LI levels in all the regions except the striatum and hippocampus. NPY-LI levels were significantlyhigher in a number of cortical regions, e.g. motor areas of the frontal cortex, anterior cingulate cortex, frontal cortex, temporal cortex and occipital cortex, compared with those in the control. NPY-LI, however, was reduced in the striatum. SS-LI also tended to be high in the cortical regions after HPD-DD treatment, but significant increases were only found in the lateral prefrontal cortex and anterior cingulate cortex. SS-LI in the striatum was significantly lower than that of the control (Fig. 2).
Discussion
We found an elevation in the NPY content of the cerebral cortex, and a reduction in the striatum following HPD-DD administration. The dosage, 50 mg/kg of HPD-DD, is equivalent to a daily oral dose of 2.5 mg/kg of HPD. 1° Smialowska and Legutko 11have found an increase in NPY levels in the locus coeruleus but not in the striatum after injecting HPD every 6 h (2.5 mg/kg, ip) for 24 h in rats. The cortical content of the peptide was not
INCREASE
IN CORTICAL
NPY AND SOMATOSTATIN
159
BY HALOPERIDOL
Table Effect of acute injection of h a l o p e r i d o l o n regional b r a i n n e u r o p e p t i d e Y - a n d somatostatin-like i m m u n o r e a c t i v i t y levels
Reyions
Neuropeptide Y Control Haloperidol
Medial prefrontal cortex Lateral prefrontal cortex Anterior cingulate cortex Posterior cingulate cortex Motor areas of frontal cortex Temporal cortex Parietal cortex Occipital cortex Striatum Hippocampus Amygdala Hypothalamus
0.148___0.023 0.159±0.021 . . 0.116±0.004 0,138±0.015 . 0,175±0.010 0,086 ± 0.002 0.128 ±0.002 0.200 ± 0.043 0.631+_0.040
Somatostatin Control Haloperidol
0.171 ±0.021 1.252±0.126 0.181+__0.023 0.664+0.073 . . . . . . 0.131 ±0.004 1.010±0.040 0.168±0.012 0.978-t-0.164 . . . 0.206±0.012 1.443±0.129 0.088 ± 0.007 0.770 ± 0.100 0.109_+0.005 1.350_+0.050 0.254±0.043 2.620 ± 0.323 0.757___0.050 2.453±0.435
1.505+0.071 0.711 ±0.059 1.160±0.040 1.284-1-0.096 1.642±0.170 0.690 ± 0,050 1.230 ±0.070 2.310+0.155 2.384±0.192
Neuropeptide Y- and somatostatin-like immunoreactivity levels are expressed as pg//~g protein. (Mean_+ SEM). Six animals were used in each experiment, Haloperidol, 1 mg/kg, was administered intraperitoneally 4 b before sacrifice.
1.0.
0.9 ¸
1"3 control II
HPD
0.8,
0.7 ¸
=
0.6
e
o. 0.5
3 ..i
z
11.4
0.3 ¸
.d
**
~h
--r
2
0.2'
0.1 ¸
0.0 mPFC IPFC aCg pCg
FC
TC
PC
OC
St
Hp
Am
Ht
Fig. 1 Regional brain neuropeptide Y-like immunoreactivities (NPY-LI) following haloperidol decanoate depot (HPD, 50 mg/kg) in rats. Abbreviations used are as follows: mPFC; medial prefrontal cortex, IPFC; lateral prefrontal cortex, aCg; anterior cingulate cortex, pCg; posterior cingulate cortex, FC; motor areas of the frontal cortex, TC; temporal cortex, PC; parietal cortex, OC; occipital cortex, St; striatum, Hp; hippocampus, Am; amygdala, and Ht; hypothalamus. The vertical bars are m e a n ± SEM. *: P < 0.05 and **: P < 0.01.
0
mPFCIPFC aCg pCg
FC
TC
PC
OC
St
Hp
Am
Ht
Fig. 2 Regional brain somatostatin-like immunoreactivities (SS-LI) following haloperidol decanoate depot (HPD, 50 mg/kg) in rats. Abbreviations used are the same as in Figure 1. The vertical bars are mean+_SEM. *: P < 0.05 and **: P < 0.01.
160 determined in their study. Long-term treatment with H P D has been reported to increase NPY staining in the arcuate nucleus. 12 Our results are partly consistent with observations by Miyake et al. 13 They found that the content of NPY is decreased in the caudate-putamen, but increased in lateral prefrontal cortex, and does not change in the other cortical areas examined after repeated ip injections of 5 mg/kg of H P D for 21 days. The differences between our results are a matter of speculation. The route of administration of H P D was different in the two studies however. Stress associated with daily ip injection, may have affected cortical NPY content in their study. Psychological stress has been demonstrated to reduce CSF NPY concentrations in man. 14 An ip injection produces a rapid increase and a rapid decrease in drug concentrations in the circulation and probably in the brain. Plasma H P D levels are remarkably stable following H P D - D D , compared with those during oral or ip administration of the drug.l° Therefore, the different pharmacodynamics due to the different administration route and/or the different formula of the drugs might be responsible for the difference in the results. In the present study, NPY levels in the cortex, including the temporal cortex, were increased after the administration of H P D - D D . Frederiksen et al 2 have shown reduced concentrations of NPY in the temporal cortex but not in the hypothalamus of the brains from schizophrenic patients, although normal tissue concentrations of NPY have also been reported in postmortem amygdala.~5 The temporal lobe seems to be a candidate site for schizophrenia since positron emission tomography studies have shown a lower metabolic rate in the temporal lobe, as well as the frontal lobe. 16 However, N P Y levels in CSF of drug-free chronic schizophrenics were reported to be higher than in controls? Normal N P Y but reduced peptide YY concentrations in CSF were observed in drug-free schizophrenic patients, iv Berrettini et a118 have observed no differences in CSF NPY levels between normal volunteers and 2-week drug-free chronic schizophrenics. No significant differences were found after treating schizophrenic patients for 4 weeks with fluphenazine either. These findings suggest that if N P Y is involved in the pathogenesis of schizophrenia, an abnormality is not detectable in the CSF. In the present study we found that acutely
NEUROPEPTIDES injected H P D was without effect on NPY or SS concentrations in rats. In general, 2 or more weeks are necessary to obtain the therapeutic effect of H P D in the treatment of schizophrenia. Thus, the treatment with H P D of schizophrenic patients could elevate or normalize reduced NPY levels in the cerebral cortex of the brain. In the present study, the effect of H P D - D D on N P Y concentrations in the striatum was different from that in the cortex. Striatal NPY content was reduced and cortical NPY was elevated following treatment with HPD. The effects of dopaminergic transmission on NPY levels seem to be region-specific. We have shown a statistically-significant reduction in striatal N P Y concentrations following 6-hydroxydopamine, a dopamine neurotoxin, or sulpiride, a selective D2 antagonist. 19 An opposite role of D2 receptors in the striatum from that in the cortex is suggested in the regulation by dopamine of N P Y metabolism? ° SS concentrations were also decreased in the striatum following H P D - D D administration in the present study. Beal and Martin 2I administered H P D at a dose of 2.5 mg/kg, ip for 3 weeks to rats and observed a reduction of SS levels in the striatum. This finding is replicated by Radke et a122who have demonstrated a reduction in SS concentrations in the caudate-putamen and nucleus accumbens in the rats given with H P D for 3 weeks in the drinking water. We found an increase in SS content in a limited number of cortical areas in this study. Beal and Martin 21 found an insignificant reduction of SS levels by H P D in prefrontal cortex, and they examined no other cortical areas. Radke et a122 found that SS content in the cortex was unaltered after 3 weeks or 8 months of H P D treatment. There has been no other report describing HPD-induced changes in SS context in the cortex. The effect of H P D on cortical SS seems to be limited, compared to NPY. Reduced concentrations of SS have been found in discrete areas of schizophrenic brains. 5 Bissette et al 6 have reported that SS is reduced in CSF from patients with schizophrenia. Reduced SS levels could also be increased in the cerebral cortex of the brains of schizophrenic patients following treatment with HPD. References 1. Heilig, M. and Widerl6v, E. Neuropeptide Y: an overview
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