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Effects of phencyclidine administration on behavior and brain neurotensin-like immunoreactivity in rats
Brain Research, 333 (1985) 393- 396 Elsevier
393
BRE 20777
Effects of phencyclidine administration on behavior and brain neurotensin-like immunoreactivity in rats MANABU WACHI. MASAHIDE OKUDA. SHUNJI TOGASHI. SEIICHI FUWANO and OSAMU MIYASHITA Department of Psychiatry, School of Medicine, and Department of Neurochemistry, Brain Research Institute, Niigata University, Asahimachi 1, Niigata 9.51 (Japan)
(Accepted December 1lth, 1984) Key word~: phencyclidine - - behavioral abnormalities -- frontal cortex -- neurotensin-like immunoreactivity
The effects of acute and chronic phencyclidine (PCP) administration on neurotensin-like immunoreactivity (NTLI) were investigated in discrete regions of rat brain. Both acute and chronic administration of PCP induced high locomotor activity, stereotypy and ataxia. On PCP administration, NTLI decreased significantly in the frontal cortex (Fc) alone. These results suggest that the decrease in NTLI in Fc is related to the behavioral abnormalities produced by PCP.
Phencyclidine [L-(L-phenyicyclohexyl)-piperidine; PCP], a potent psychotomimetic drug, produces psychoses in man and behavioral abnormalities in animals 17. The behavioral abnormalities characterized by a complex behavioral pattern which consists of high locomotor activity, stereotyped behavior and ataxia are similar but not identical to those induced by D-amphetamine 1~. Several studies have suggested that PCP affects a number of neurotransmitter systems such as the 5-hydroxytryptamine (5HT), dopamine ( D A ) , acetylcholine (ACh) and yaminobutyric acid ( G A B A ) systems~. 11, but the neurochemical mechanisms of the behavioral abnormalities induced by PCP have not been well established. Neurotensin (NT), a tridecapeptide, shows a variety of pharmacological properties which are similar to those of neuroleptics ~4. For example, Nemeroff et al. 15 observed that NT intracisternally administered to mice and rats significantly attenuated the behavioral hyperactivity that had been produced by administration of D-amphetamine, methylphenidate or cocaine. Therefore, we have examined the effect of PCP on neurotensin-like immunoreactivity (NTLI) in discrete regions of rat brain. Male Wistar rats, weighing 140-210 g, were used
in the experiment. The rats were group-housed (5 rats per cage) in a temperature-controlled room (22 + 2 °C) with a 12 h light-dark schedule. Oriental Laboratory Chow (Oriental Yeast. Tokyo) and tap water were provided ad libitum. The rats were divided into 3 groups as follows: (1) control group, rats received saline for 10 days; (2) acute PCP group, rats received saline for 9 days and PCP-HCI (1(I mg/kg) on the 10th day; and (3) chronic PCP group, rats received PCP-HCI (10 mg/kg) daily for 10 days. PCP-HCI (Research Triangle Institute, NC, U.S.A.) was dissolved in saline and injected intraperitoneally. The locomotor activity, stereotyped behavior and ataxia were assessed separately by two highly trained observers according to the procedure described by Sturgeon et al.18. This procedure utilizes a rating scale, ranging from 0 to 5, which best describes these behaviors. On the 10th day the rats were rated for 30 s at 10-min intervals for a period of 1 h after drug injection and then killed by decapitation. The brain was removed and discrete regions were dissected out of coronal slices obtained by following the anterior posterior planes of K6nig and Klippel's atlasl0: midbrain (MB), 1610-2790ktm; hypothalamus (HT), 2790-7190 ~m; limbic forebrain (LF) and caudateputamen (CP), 7 8 9 0 - 9 8 2 0 ~ m ; and frontal cortex
Correspondence: M. Wachi. Department of Psychiatry, School of Medicine. Niigata University, Asahimachi 1. Niigata 951, Japan.
0006-8993;85/$03.30 © 1985 Elsevier Science Publishers B.V. (Biomedical Division)
394
(Fc), 9820,um. Fc included the cerebral cortex but not the olfactory bulb. I,F, including the nucleus accumbens and olfactory tubercle, was taken out using the anterior commissure and thc rhinal fissure as landmarks. CP dorsal to the anterior commissure was obtained by cutting along the scptal and cortical borders of the slice. HT was dissected out by taking the anterior commissure as a horizontal reference. MB, dissected out using the aqueductus cerebri as a landmark. contained most of the substantia nigra. NT-keyhole limpet haemocyanin conjugate was made by the method of Uhl and Snvder -'~'as follows: 6 mg of NT (Protein Research Foundation. Osaka, Japan) and 20 mg of keyhole limpet hacmocyanin (Calbiochem, CA, U.S.A.) were incubated with 100 mg l-cthyl-3-(3-dimethylammopropyl)carbodiimide-HCl (Sigma) for 30 min at 25 °C. and then the mixture was dialysed overnight. Rabbits received multiplc intradermal injections of the NT-haemocyanin conjugate (2 mg) mixed with complete Freund's adjuvant (Difco) and, subsequently, two booster injections every two weeks each of 0.5 mg of NT-hacmocyanin conjugate mixed with incomplete Freund's adjuvant. The antiserum prepared by this procedure cross-reacted at about 27~?: with NT~.~ and at less than 0.01% with NT~_I~ compared to the reactivity with N'I'~-J3 but failed to cross-react with other peptides, including enkephalins, substance P, thyrotropin-releasing hormone and cholecystokinin-8. l'issucs werc homogenized in 30 vols. of 2 N acetic acid. The supernatants obtained after centrifugation (15(10 rpm. 10 min, 4 ~(') were freeze-dried. The frccze-dried samples werc resuspended in 1 ml of sodium phosphate buffer (50 mM, pH 7.4) containing (I.1:'~ gelatin and 0.()lC~ NaN 3 (assay buffer), and then aliquots of the suspension were taken for N T radioimmunoassay (NT-R1A). N T - R I A was carricd out by the method of Carraway and LecmanL NT was iodinated by the chloraminc T method and purified by Sephadex gel permeation chromatography. The 350/A assay mixtures contained 5(I t~1 of anti-NT scrum diluted 1:14,000. 50.ul of [l-'~I]NI" (approximatcly 10,000 cpm), 50/¢1 of standard synthetic NT or of brain extract, and 200 ill of the assay buffer. Aftcr incubation at 4 °C for 24 h, 1 ml of charcoal-dextran solution was added to each tube, and further incubated for 30 rain at 4 ~C. Then after centrifugation at 300(I rpm for 311 rain. the antibody
bound [I-~51]NTwas measured with a gamma counter. All assays were performed in triplicate and the means were taken. All of the samples v~crc mcasurcd in a single RIA. NTLI of the extracts w~ts calcuhttcd from calibration curve prepared b~ synthetic NI. The sensitivity of the assa~ was 10 pg/tubc. With this technique, the rccovery of NT added as ,m internal standard to tissue extracts was more than ~":~. Student's t-test was used for all statistical analyses. Fig. 1 shows the effects of PCP (10 mg, kg) on behavior. Acute PCP administration (A)induced high locomotor activity, stereotyped behavior and ataxia. PCP-induced locomotor activity was elcw~tcd significantly by' further administration of PCP lot 9 days (P < 0.001). On the othcr hand. after 10 d,lys of PCP administration, both the PCP-induced stereotyped behavior and ataxia ratings decreased significantly (P < I).01) as compared with those in the ~tcute PCP group. In the control group, high locomot~Jr activity. stereotyped behavior and ~taxia were ne',.cr observed. Our N T - R I A study revealed a high level of NTLI in HT. an intermediate level of NTLI in LF and MB. and a low level of NTLI in Fc and CP of the control animals (Table 1). As shown in Fig. 2. NTLI in Fc of "A"P~O.O01 compared to Comrol t ('o J
~, ~ P/~O.OI, :,~-~-.~ P~O.O01 compared to a c u t e P ( ' P
I [ :
")(%-)(T
I
~..l
.
3-
i?!i
,liiii I
I
',:.":
2:
~iiiii,
!i!ii
~., ,,
(o
A
Ch
locomotion
o ('o
I!
iiiiil_o ('h
stereotyp~
t'o
A
('h
ataxia
Fig. 1. Effect of administration of PCP (10 mg/kg) once (A) or once a day for 10 days (Cb) on locomotion, stereotypy and ataxia. Each column shows the mean rating of the behavior of 8 rats averaged over a 60-rain observation period: vertical bars; denote S.E.M. *P < 0.05. "*P < 0.(~1 (as comparcd with control values shown in Table I).
395 TABLE I
Neurotensin-like immunore~ctivitv (NTLI) in 5 areas of the brain o]the control group (pg/mg wet weight) Fc, frontal cortex: Cp, caudate-putamen; LF, limbic forebrain; I H , hypothalamus; MB, midbrain.
A rea
Control group (n = 6)
Fc
CP
LF
liT
MB
2.89 +_ 0.07
3.12 +_ 0.20
16.3 _ 1.4
75.0 +_ 3.11
32.6 _+ 2.4
the acute PCP group was significantly lower than that in the control group, and after 10 daily PCP injections almost the same degree of decrease in NTLI was still observed in Fc. In LF, CP, HT and MB in both the acute and chronic groups, NTLI was not significantly different from that in the control group. In the present study, both acute and chronic PCP administration produced high locomotor activity, stereotyped behavior and ataxia in rats, in good agreement with the report of Sturgeon et al.19. It has been shown that PCP pretreatment enhances amphetamine-induced stereotypy in rats, suggesting that PCP has dopaminergic activity similar to amphetamine-L Other workers have demonstrated that ~,11.1
( % of t'ontrol
2O
(
L
h L
.
.
.
~ .
.
.
.
_
)
6O ,__.
I00 t
~
.
CP Ch i ±
1.1: ('h
I i
i ~-"-
i i
(h Fig. 2. Effects of acute (A) and chronic (Ch) administration of PCP on neurotcnsin-like immunoreactivity (NTLI) in discrete areas of rat brain. Each column is thc mean of 6 experiments: vertical bars denote S.E.M. * P < 0.05, ** P < 0.01 (as compared with control values shown in 'Fablc I).
PCP-induced stereotyped behavior was antagonized by neuroleptic agents such as chlorpromazine, haloperidol and pimozide, but not by a- or/~-adrenergic blockers 12. It has also been reported that PCP stimulates the release of [3H]dopamine from slices of the rat striatum I and inhibits the uptake of [3H]dopamine by synaptosome-rich homogcnates of the rat striaturn ~,. All of these reports indicated that PCP enhanced central dopaminergic activity. In our study, NTLI decreased significantly in Fc but not in CP, LF, HT or MB in both the acute and chronic PCP groups. It has been reported that selective lesions of the dopaminergic system in thc prefrontal cortex enhance spontancous motor activity and amphetamine-induced stereotyped behavior, and it has been suggested that the prefrontal cortex has some influence on subcortical dopaminergic transmission 4. Direct injcction of NT into the nucleus accumbens blocks D-amphetaminc-induccd locomotion and rearingL Furthermore, direct injection of NT into the ventral tegmcntal area produces behavioral hyperactivity and increases thc concentration of homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens and olfactory tubercles but not in the striatum v. Moreover, it has been reported that chronic administration of antipsychotic drugs increased the concentration of ncurotensin in nucleus accumbcns and striaturn 7. These behavioral and ncurochemical studies lead to one conclusion that NT is capable of modulating dopamincrgic transmission in the central nervous system. Thus, we suggest that the PCP-induced decrease in NTLI in Fc of rat affects subcortical dopaminergic activities, resulting in behavioral abnormalities such as high locomotor activity and stereotyped behavior. In the present experiment, a significant difference in NTLI was not observed between the acute and chronic PCP groups, although a further incrcase in
31115 l o c o m o t o r activity and d e c r e a s e s m s t e r e o t y p e d be-
related to n e u r o c h e m i c a l m e c h a n i s m s ,~; I ' C P p s }
h a v i o r and ataxia w e r e o b s e r v e d in the c h r o n i c P C P
choses. It may be speculative, but our data seem to
g r o u p c o m p a r e d with the acute P C P group. At pres-
bear s o m e analogy with a p r e v i o u s rcport-'J that a
ent, it is not possible to relate o u r n e u r o c h e m i c a l
s u b p o p u l a t i o n of s c h i z o p h r e n i c s s h o w e d , reduction
findings to the i n c r e a s e d l o c o m o t o r activity and the
of N T in the c e r e b r o s p i n a l fluid (CS[:i and normali-
d e c r e a s e d s t e r e o t y p e d b e h a v i o r and ataxia in the
zation of C S F levels of N [ after n e u r o l e p t i c treat-
chronic P C P group. It has b e e n r e p o r t e d that c h r o n i c
ment.
PCP a d m i n i s t r a t i o n leads to the d e v e l o p m e n t of tole r a n c e as to the s t e r e o t y p e d b e h a v i o r and ataxia, and
C o m m e n t s on the m a n u s c r i p t by Dr. M. Satakc,
a p p a r e n t supersensitivity as to the l o c o m o t o r activ-
Dr. S. l h d a and Dr. H. N a i t o are gratefully a c k n o w -
ity v~. and that the d e v e l o p m e n t of t o l e r a n c e as to
ledged. T h e a u t h o r s are greatly i n d e b t e d to Mr. K.
P C P - i n d u c e d m o t o r i n c o o r d i n a t i o n is r e l a t e d to the
H. Davis, Jr. ( R e s e a r c h T r i a n g l e Institute) for gifts
e n k e p h a l i n e r g i c n e u r o n a l system 13.
of p h e n c y c l i d i n e and to Dr. N. Y a n a i h a r a ( S h i z u o k a
As for P C P psychosis, it might be a s s u m e d that the
C o l l e g e of P h a r m a c y ) ff)r gifts of N T I s.
r e d u c t i o n of N T L I i n d u c e d by P C P a d m i n i s t r a t i o n is
1 Ary, T. E. and Kimiskey, H. L.. Phencyclidine-induced rclease of [3H]dopamine from chopped striatal tissue, Neuropharmacology, 21 (1982)639-645. 2 Balstcr, R. L. and Chait. L. I)., Thc effects of phencyclidine on amphetamine stereotypy in rats. Europ. J. Pharmacol.. 48 (1978) 445-450. 3 Carraway, R. and Leeman, S. E., Radioimmunoassay for neurotensin, a hypothalamic peptide. J. bioL ('hem.. 251 (1976) 71135-71144. 4 Carter, C. J. and Pycock. C. J.. Behavioral and biochemical effects of dopaminc and noradrenaline depletion within the medial prefrontal cortex of the rat. Brain Research. 192 (1980) 163- 176. 5 Ervin, G. N., Birkcmo, L. S.. Ncmeroff, C. B. and Prange, A. J., Jr., Neurotensin blocks certain amphetamine-induced behaviours, Nature (Lond.). 291 (1981) 73-76. 6 Garey, R. E. and Heath, R. G., The effect of phencyclidine on the uptake of ~H-catccholamines by rat striatal and hypothalamic synaptosomcs, Life Sci.. 18 (1976) 1105- I 1ltl. 7 Govoni. S., Hong. J. S.. Yang, H.-Y. T. and Costa, E., Increase of neurotensin content elicited by neurolcptics in nucleus accumbens, J. Pharmacol. exp. Ther.. 215 (198111 413--417. 8 Hsu, L. L., Smith, R. C., Rolsten, C and Leelavathi, D. E.. Effects of acute and chronic phencyclidine on neurotransmitter enzymes in rat. Biochem. Pharmacol., 29 (1980) 2524-2526. 9 Kalivas. P. W.. Burgess, S. K., Nemcroff, ( . B. and Prange, A. J., Jr., Behavioral and neurochemical effects of ncurotensin microinjection into the ventral tegmental area of the rat, Neuroscience, 8 (1983) 495-5115. 111 K,3nig, J. F. R. and Klippel, R. A., The Rat Brain. Robert E. Krieger Publishing, New York, 1963. 11 Martin, J. R., Berman, M. H., Krcusun, I. and Small, S. F., Phencyclidine-induced stereotyped behavior and serotonergic syndrome in rat. Life Sci.. 24 (1979) 1699-17113.
12 Murry, T. F. and Horita, A., Phencyclidine-induced stereotyped behavior in rats: dose response effects and antagonism by neuroleptics, Life Sci.. 24 (1979) 2217-2226. 13 Nabeshima, "I., Hiramatsu, M., Amano, M.. Furukawa, H. and Kameyama, T., Chronic phencyclidine increases methionine-enkephaline level in mouse striatum, Neurosci. Lett.. 37 (1983) 69-74. 14 Nemeroff, C. B., Neurotensin: perchance an endogenous neuroleptic?, Biol. Psychiat.. 15 ( 19801 283-3112. 15 Nemeroff, C. B., Hernandez, D.. Luttingcr. D.. Kalivas. P. W. and Prange, A. J., Jr., Interactions of neurotensin with brain dopamine systems. Attn. N.Y. Acad. Sci., 400 (1982) 33()- 344. 16 Robertson, H. A.. Chronic D-amphetamine and phencyclidine: effects on dopamine agonist and antagonist binding sites in the extrapyramidal and mesolimbic systcms, Brain Research, 267 (1983) 179-182, 17 Snyder, S. H., Phencyclidine. Nature (Lond.~. 285 (19801 355-356. 18 Sturgeon, R. D., Fessler, R. G. and Meltzcr, H. Y.. Behavioral rating scales for assessing phencyclidine-induced locomotor activity, stereotyped behavior and ataxia in rats, Europ. J. PharmacoL , 59(1979) 169-179. 19 Sturgeon. R. D., Fessler, R. G., London, S. 1- and Meltzer, H. Y., Behavioral effects of chronic phencyclidine administration in rats, Psychopharmacology, 76 (19821 52-56. 20 Uhl, G. R. and Snydcr, S. !-I., Rcgional and subcellular distribution of brain neurotensin, l,ifi, Sci.. 19 (1076) 1827-1832. 21 Widerl6v. E.. Lindstrom, L. H.. Besev, G., Manbcrg. P. J., Ncmeroff, C. B., Breese, G. R.. Kizer, J. S. and Prange, A. J., Jr., Subnormal CSF levels of neurotensin in u subgroup of schizophrenic patients: normalization after neuroleptic treatment, Amer. J. Psychiat.. 139 (19821 1122.- 1126.
393
BRE 20777
Effects of phencyclidine administration on behavior and brain neurotensin-like immunoreactivity in rats MANABU WACHI. MASAHIDE OKUDA. SHUNJI TOGASHI. SEIICHI FUWANO and OSAMU MIYASHITA Department of Psychiatry, School of Medicine, and Department of Neurochemistry, Brain Research Institute, Niigata University, Asahimachi 1, Niigata 9.51 (Japan)
(Accepted December 1lth, 1984) Key word~: phencyclidine - - behavioral abnormalities -- frontal cortex -- neurotensin-like immunoreactivity
The effects of acute and chronic phencyclidine (PCP) administration on neurotensin-like immunoreactivity (NTLI) were investigated in discrete regions of rat brain. Both acute and chronic administration of PCP induced high locomotor activity, stereotypy and ataxia. On PCP administration, NTLI decreased significantly in the frontal cortex (Fc) alone. These results suggest that the decrease in NTLI in Fc is related to the behavioral abnormalities produced by PCP.
Phencyclidine [L-(L-phenyicyclohexyl)-piperidine; PCP], a potent psychotomimetic drug, produces psychoses in man and behavioral abnormalities in animals 17. The behavioral abnormalities characterized by a complex behavioral pattern which consists of high locomotor activity, stereotyped behavior and ataxia are similar but not identical to those induced by D-amphetamine 1~. Several studies have suggested that PCP affects a number of neurotransmitter systems such as the 5-hydroxytryptamine (5HT), dopamine ( D A ) , acetylcholine (ACh) and yaminobutyric acid ( G A B A ) systems~. 11, but the neurochemical mechanisms of the behavioral abnormalities induced by PCP have not been well established. Neurotensin (NT), a tridecapeptide, shows a variety of pharmacological properties which are similar to those of neuroleptics ~4. For example, Nemeroff et al. 15 observed that NT intracisternally administered to mice and rats significantly attenuated the behavioral hyperactivity that had been produced by administration of D-amphetamine, methylphenidate or cocaine. Therefore, we have examined the effect of PCP on neurotensin-like immunoreactivity (NTLI) in discrete regions of rat brain. Male Wistar rats, weighing 140-210 g, were used
in the experiment. The rats were group-housed (5 rats per cage) in a temperature-controlled room (22 + 2 °C) with a 12 h light-dark schedule. Oriental Laboratory Chow (Oriental Yeast. Tokyo) and tap water were provided ad libitum. The rats were divided into 3 groups as follows: (1) control group, rats received saline for 10 days; (2) acute PCP group, rats received saline for 9 days and PCP-HCI (1(I mg/kg) on the 10th day; and (3) chronic PCP group, rats received PCP-HCI (10 mg/kg) daily for 10 days. PCP-HCI (Research Triangle Institute, NC, U.S.A.) was dissolved in saline and injected intraperitoneally. The locomotor activity, stereotyped behavior and ataxia were assessed separately by two highly trained observers according to the procedure described by Sturgeon et al.18. This procedure utilizes a rating scale, ranging from 0 to 5, which best describes these behaviors. On the 10th day the rats were rated for 30 s at 10-min intervals for a period of 1 h after drug injection and then killed by decapitation. The brain was removed and discrete regions were dissected out of coronal slices obtained by following the anterior posterior planes of K6nig and Klippel's atlasl0: midbrain (MB), 1610-2790ktm; hypothalamus (HT), 2790-7190 ~m; limbic forebrain (LF) and caudateputamen (CP), 7 8 9 0 - 9 8 2 0 ~ m ; and frontal cortex
Correspondence: M. Wachi. Department of Psychiatry, School of Medicine. Niigata University, Asahimachi 1. Niigata 951, Japan.
0006-8993;85/$03.30 © 1985 Elsevier Science Publishers B.V. (Biomedical Division)
394
(Fc), 9820,um. Fc included the cerebral cortex but not the olfactory bulb. I,F, including the nucleus accumbens and olfactory tubercle, was taken out using the anterior commissure and thc rhinal fissure as landmarks. CP dorsal to the anterior commissure was obtained by cutting along the scptal and cortical borders of the slice. HT was dissected out by taking the anterior commissure as a horizontal reference. MB, dissected out using the aqueductus cerebri as a landmark. contained most of the substantia nigra. NT-keyhole limpet haemocyanin conjugate was made by the method of Uhl and Snvder -'~'as follows: 6 mg of NT (Protein Research Foundation. Osaka, Japan) and 20 mg of keyhole limpet hacmocyanin (Calbiochem, CA, U.S.A.) were incubated with 100 mg l-cthyl-3-(3-dimethylammopropyl)carbodiimide-HCl (Sigma) for 30 min at 25 °C. and then the mixture was dialysed overnight. Rabbits received multiplc intradermal injections of the NT-haemocyanin conjugate (2 mg) mixed with complete Freund's adjuvant (Difco) and, subsequently, two booster injections every two weeks each of 0.5 mg of NT-hacmocyanin conjugate mixed with incomplete Freund's adjuvant. The antiserum prepared by this procedure cross-reacted at about 27~?: with NT~.~ and at less than 0.01% with NT~_I~ compared to the reactivity with N'I'~-J3 but failed to cross-react with other peptides, including enkephalins, substance P, thyrotropin-releasing hormone and cholecystokinin-8. l'issucs werc homogenized in 30 vols. of 2 N acetic acid. The supernatants obtained after centrifugation (15(10 rpm. 10 min, 4 ~(') were freeze-dried. The frccze-dried samples werc resuspended in 1 ml of sodium phosphate buffer (50 mM, pH 7.4) containing (I.1:'~ gelatin and 0.()lC~ NaN 3 (assay buffer), and then aliquots of the suspension were taken for N T radioimmunoassay (NT-R1A). N T - R I A was carricd out by the method of Carraway and LecmanL NT was iodinated by the chloraminc T method and purified by Sephadex gel permeation chromatography. The 350/A assay mixtures contained 5(I t~1 of anti-NT scrum diluted 1:14,000. 50.ul of [l-'~I]NI" (approximatcly 10,000 cpm), 50/¢1 of standard synthetic NT or of brain extract, and 200 ill of the assay buffer. Aftcr incubation at 4 °C for 24 h, 1 ml of charcoal-dextran solution was added to each tube, and further incubated for 30 rain at 4 ~C. Then after centrifugation at 300(I rpm for 311 rain. the antibody
bound [I-~51]NTwas measured with a gamma counter. All assays were performed in triplicate and the means were taken. All of the samples v~crc mcasurcd in a single RIA. NTLI of the extracts w~ts calcuhttcd from calibration curve prepared b~ synthetic NI. The sensitivity of the assa~ was 10 pg/tubc. With this technique, the rccovery of NT added as ,m internal standard to tissue extracts was more than ~":~. Student's t-test was used for all statistical analyses. Fig. 1 shows the effects of PCP (10 mg, kg) on behavior. Acute PCP administration (A)induced high locomotor activity, stereotyped behavior and ataxia. PCP-induced locomotor activity was elcw~tcd significantly by' further administration of PCP lot 9 days (P < 0.001). On the othcr hand. after 10 d,lys of PCP administration, both the PCP-induced stereotyped behavior and ataxia ratings decreased significantly (P < I).01) as compared with those in the ~tcute PCP group. In the control group, high locomot~Jr activity. stereotyped behavior and ~taxia were ne',.cr observed. Our N T - R I A study revealed a high level of NTLI in HT. an intermediate level of NTLI in LF and MB. and a low level of NTLI in Fc and CP of the control animals (Table 1). As shown in Fig. 2. NTLI in Fc of "A"P~O.O01 compared to Comrol t ('o J
~, ~ P/~O.OI, :,~-~-.~ P~O.O01 compared to a c u t e P ( ' P
I [ :
")(%-)(T
I
~..l
.
3-
i?!i
,liiii I
I
',:.":
2:
~iiiii,
!i!ii
~., ,,
(o
A
Ch
locomotion
o ('o
I!
iiiiil_o ('h
stereotyp~
t'o
A
('h
ataxia
Fig. 1. Effect of administration of PCP (10 mg/kg) once (A) or once a day for 10 days (Cb) on locomotion, stereotypy and ataxia. Each column shows the mean rating of the behavior of 8 rats averaged over a 60-rain observation period: vertical bars; denote S.E.M. *P < 0.05. "*P < 0.(~1 (as comparcd with control values shown in Table I).
395 TABLE I
Neurotensin-like immunore~ctivitv (NTLI) in 5 areas of the brain o]the control group (pg/mg wet weight) Fc, frontal cortex: Cp, caudate-putamen; LF, limbic forebrain; I H , hypothalamus; MB, midbrain.
A rea
Control group (n = 6)
Fc
CP
LF
liT
MB
2.89 +_ 0.07
3.12 +_ 0.20
16.3 _ 1.4
75.0 +_ 3.11
32.6 _+ 2.4
the acute PCP group was significantly lower than that in the control group, and after 10 daily PCP injections almost the same degree of decrease in NTLI was still observed in Fc. In LF, CP, HT and MB in both the acute and chronic groups, NTLI was not significantly different from that in the control group. In the present study, both acute and chronic PCP administration produced high locomotor activity, stereotyped behavior and ataxia in rats, in good agreement with the report of Sturgeon et al.19. It has been shown that PCP pretreatment enhances amphetamine-induced stereotypy in rats, suggesting that PCP has dopaminergic activity similar to amphetamine-L Other workers have demonstrated that ~,11.1
( % of t'ontrol
2O
(
L
h L
.
.
.
~ .
.
.
.
_
)
6O ,__.
I00 t
~
.
CP Ch i ±
1.1: ('h
I i
i ~-"-
i i
(h Fig. 2. Effects of acute (A) and chronic (Ch) administration of PCP on neurotcnsin-like immunoreactivity (NTLI) in discrete areas of rat brain. Each column is thc mean of 6 experiments: vertical bars denote S.E.M. * P < 0.05, ** P < 0.01 (as compared with control values shown in 'Fablc I).
PCP-induced stereotyped behavior was antagonized by neuroleptic agents such as chlorpromazine, haloperidol and pimozide, but not by a- or/~-adrenergic blockers 12. It has also been reported that PCP stimulates the release of [3H]dopamine from slices of the rat striatum I and inhibits the uptake of [3H]dopamine by synaptosome-rich homogcnates of the rat striaturn ~,. All of these reports indicated that PCP enhanced central dopaminergic activity. In our study, NTLI decreased significantly in Fc but not in CP, LF, HT or MB in both the acute and chronic PCP groups. It has been reported that selective lesions of the dopaminergic system in thc prefrontal cortex enhance spontancous motor activity and amphetamine-induced stereotyped behavior, and it has been suggested that the prefrontal cortex has some influence on subcortical dopaminergic transmission 4. Direct injcction of NT into the nucleus accumbens blocks D-amphetaminc-induccd locomotion and rearingL Furthermore, direct injection of NT into the ventral tegmcntal area produces behavioral hyperactivity and increases thc concentration of homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens and olfactory tubercles but not in the striatum v. Moreover, it has been reported that chronic administration of antipsychotic drugs increased the concentration of ncurotensin in nucleus accumbcns and striaturn 7. These behavioral and ncurochemical studies lead to one conclusion that NT is capable of modulating dopamincrgic transmission in the central nervous system. Thus, we suggest that the PCP-induced decrease in NTLI in Fc of rat affects subcortical dopaminergic activities, resulting in behavioral abnormalities such as high locomotor activity and stereotyped behavior. In the present experiment, a significant difference in NTLI was not observed between the acute and chronic PCP groups, although a further incrcase in
31115 l o c o m o t o r activity and d e c r e a s e s m s t e r e o t y p e d be-
related to n e u r o c h e m i c a l m e c h a n i s m s ,~; I ' C P p s }
h a v i o r and ataxia w e r e o b s e r v e d in the c h r o n i c P C P
choses. It may be speculative, but our data seem to
g r o u p c o m p a r e d with the acute P C P group. At pres-
bear s o m e analogy with a p r e v i o u s rcport-'J that a
ent, it is not possible to relate o u r n e u r o c h e m i c a l
s u b p o p u l a t i o n of s c h i z o p h r e n i c s s h o w e d , reduction
findings to the i n c r e a s e d l o c o m o t o r activity and the
of N T in the c e r e b r o s p i n a l fluid (CS[:i and normali-
d e c r e a s e d s t e r e o t y p e d b e h a v i o r and ataxia in the
zation of C S F levels of N [ after n e u r o l e p t i c treat-
chronic P C P group. It has b e e n r e p o r t e d that c h r o n i c
ment.
PCP a d m i n i s t r a t i o n leads to the d e v e l o p m e n t of tole r a n c e as to the s t e r e o t y p e d b e h a v i o r and ataxia, and
C o m m e n t s on the m a n u s c r i p t by Dr. M. Satakc,
a p p a r e n t supersensitivity as to the l o c o m o t o r activ-
Dr. S. l h d a and Dr. H. N a i t o are gratefully a c k n o w -
ity v~. and that the d e v e l o p m e n t of t o l e r a n c e as to
ledged. T h e a u t h o r s are greatly i n d e b t e d to Mr. K.
P C P - i n d u c e d m o t o r i n c o o r d i n a t i o n is r e l a t e d to the
H. Davis, Jr. ( R e s e a r c h T r i a n g l e Institute) for gifts
e n k e p h a l i n e r g i c n e u r o n a l system 13.
of p h e n c y c l i d i n e and to Dr. N. Y a n a i h a r a ( S h i z u o k a
As for P C P psychosis, it might be a s s u m e d that the
C o l l e g e of P h a r m a c y ) ff)r gifts of N T I s.
r e d u c t i o n of N T L I i n d u c e d by P C P a d m i n i s t r a t i o n is
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