Plasma homovanillic acid levels and therapeutic outcome in schizophrenics: comparisons of neuroleptic-naive first-episode patients and patients with disease exacerbation due to neuroleptic discontinuance.

Plasma homovanillic acid (pHVA) levels were measured and the Brief Psychiatric Rating Scale (BPRS) scores were evaluated in 26 schizophrenic patients who had either never been medicated (neuroleptic-naive, first-episode subjects) or whose condition had become exacerbated following neuroleptic discontinuance (exacerbated subjects). All the subjects received medication with a fixed dose of a neuroleptic (haloperidol or fluphenazine, both 9 mg/day) for the first week and variable doses for the subsequent 4 weeks. In the neuroleptic-naive subjects, pHVA levels increased significantly 1 week after starting the protocol; this increase correlated significantly with clinical improvement of the BPRS positive symptom scores at week 5. In the neuroleptic-naive subjects, pHVA levels had declined to the baseline level by week 5. In the exacerbated subjects, there were no significant correlations between pHVA level changes at week 1 and later improvements of the BPRS positive symptom scores. These results suggest that the rise in pHVA levels occurring within 1 week after starting a fixed neuroleptic dose may predict a favorable clinical response in neuroleptic-naive schizophrenic patients.

Clozapine- and olanzapine-induced Fos expression in the rat medial prefrontal cortex is mediated by beta-adrenoceptors.

The atypical neuroleptics, clozapine and olanzapine, have superior therapeutic efficacy against the negative symptoms of schizophrenia, compared with the typical neuroleptics. Recently, it has been suggested that the ability of clozapine and olanzapine to induce Fos expression in the medial prefrontal cortex (mPFC), contribute to their therapeutic efficacy. However, the mechanisms underlying the neuropharmacological effects of clozapine and olanzapine in the mPFC remain elusive. In the present study, we demonstrate that clozapine- and olanzapine-induced Fos expression in the mPFC are inhibited by propranolol. We also show that clozapine and olanzapine induce Fos expression in the locus coeruleus. These results suggest that clozapine and olanzapine increase noradrenaline release by stimulating noradrenergic neuronal activity in the locus coeruleus and, consequently, increased noradrenaline induce Fos expression in the mPFC via beta-adrenergic receptors. This postulated sequence may be one of mechanisms by which clozapine-like atypical neuroleptics are more effective for the negative symptoms of schizophrenia.

Carbamazepine suppresses methamphetamine-induced Fos expression in a regionally specific manner in the rat brain. Possible neural substrates responsible for antimanic effects of mood stabilizers.

Carbamazepine (CBZ) has been widely used for treatment of manic states. Because amphetamine produces effects in humans similar to those of idiopathic mania, acute methamphetamine administration could serve as a model of this condition. To elucidate the neurobiological substrates responsible for the antimanic effects of carbamazepine, this study investigated the effects of chronic carbamazepine administration on regional Fos protein expression induced by a single dose of methamphetamine (2mg/kg). Chronic treatment with CBZ (0.25% in food for 7 days, followed by 0.5% for 7 days; final mean serum carbamazepine concentration: 4.09 +/- 0.34 microg/ml) significantly attenuated the number of Fos-like immunoreactivity-positive nuclei induced by methamphetamine administration in the core of the nucleus accumbens and the caudate/putamen. The results indicate these brain regions are involved in the antimanic effects of carbamazepine.

Amphetamine sensitization enhances regional c-fos expression produced by conditioned fear.

Chronically administered amphetamine can result in a paranoid psychosis that can be re-induced in former amphetamine abusers by psychological stressors. In an attempt to investigate the neurobiological correlates of this phenomenon, the present study examined the effects of prior D-amphetamine sensitization on regional c-fos expression induced by a psychological stressor. Rats received intermittent footshock in a distinctive environment for 30 min/day for three days. Three days after the last fear conditioning session, the animals received injections of saline or D-amphetamine (4 mg/kg, i.p.) once every second day for 16 days (eight injections in total). After a 14-day drug abstinent period, the animals were placed in the fear conditioning apparatus but without footshock. The amphetamine sensitization procedure significantly enhanced the effects of conditioned fear on c-fos expression in several brain regions. These included the cingulate cortex area 3, agranular insular cortex (layers 2 and 3), claustrum, piriform cortex, the shell region of the nucleus accumbens, medial striatum, ventral lateral septum, and CA3 and polymorphic layer of the hippocampal formation. These results indicate that D-amphetamine sensitization can have long-lasting effects on the neural circuitries activated by conditioned stressors.

Effects of selective D-1 and D-2 dopamine antagonists on development of methamphetamine-induced behavioral sensitization.

The present study examined effects of selective antagonists of D-1 and D-2 dopamine receptors on the development of behavioral sensitization produced by repeated methamphetamine (MAP) administration. Male Sprague-Dawley rats were divided into four groups. Each group received a daily injection of saline (control group), 4 mg/kg MAP (MAP group), 1 mg/kg YM-09151-2 plus 4 mg/kg MAP (YM + MAP group) or 0.5 mg/kg SCH 23390 plus 4 mg/kg MAP (SCH + MAP group) for 14 days. During daily injection for 14 days, the MAP group exhibited a progressive augmentation in locomotor and stereotyped behavior, whereas the progression of such behaviors in the YM + MAP and SCH + MAP group was completely prevented. After an abstinence period of 7 days, all groups received a challenge of 2 mg/kg MAP. The MAP challenge reproduced hyperlocomotion and intense stereotyped behavior only in the MAP group. However, neither the YM + MAP group nor the SCH + MAP group showed stereotypy. The manner in which both groups showed only hyperlocomotion was similar to that observed in the control group. These results indicate that both selective D-1 antagonists and selective D-2 antagonists not only reverse MAP-induced motor effects at each injection but also prevent the development of behavioral sensitization induced by repeated MAP administration.

The effect of lithium on methamphetamine-induced regional Fos protein expression in the rat brain.

Lithium has been used widely for the treatment of manic states. Since amphetamines produce effects in humans similar to the symptoms of idiopathic mania, amphetamine administration to animals has been proposed as a model of this condition. To investigate the neurobiologic substrates of the antimanic effects of chronic lithium administration, we investigated its effects on methamphetamine-induced regional Fos protein expression in the rat brain. Chronic lithium administration (14 days; serum lithium concentration, 0.41+/-0.02 mEq/l) significantly reduced the number of neuronal nuclei showing immunoreactivity induced by methamphetamine (2mg/kg) in the prefrontal cortex, caudate/putamen, nucleus accumbens, and central nucleus of the amygdala. These results indicate the structural basis in CNS which is responsible for the antimanic effect of lithium.

Amphetamine sensitization augments amphetamine-induced Fos expression in the lateral habenula.

Repeated amphetamine (AMPH) administration results in behavioral sensitization. To investigate the neuroanatomical basis of this phenomenon, we examined the effects of AMPH sensitization on AMPH-induced Fos expression in 24 regions of the rat brain. Rats received repeated injections of AMPH (4 mg/kg, intraperitoneally, once every other day, eight times in total) or saline (same schedule as for AMPH). After a 14-day drug abstinence period, rats were challenged with 2 mg/kg AMPH intraperitoneally. As measured by Fos immunohistochemistry, the AMPH sensitization procedure enhanced subsequent AMPH-induced Fos expression in only one structure, the medial part of the lateral habenula. These results indicate that AMPH-induced behavioral sensitization is not accompanied by widespread increases in the ability of AMPH to increase regional Fos expression in the forebrain. The lateral habenula appears to be involved in the possible neural framework that is responsible for the expression of behavioral sensitization.

Ceruletide suppresses endogenous dopamine release via vagal afferent system, studied by in vivo intracerebral dialysis.

Ceruletide, a cholecystokinin-related decapeptide, has been reported to have some therapeutic effects on tardive dyskinesia and other involuntary movement disorders. In order to clarify the effects of ceruletide on dopaminergic activity in the rat striatum, we measured the release of endogenous dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) after intraperitoneal administration of ceruletide (2, 20, 200 micrograms/kg) using in vivo intracerebral dialysis techniques. After administration of ceruletide (200 micrograms/kg), extracellular DA decreased significantly (P less than 0.05) for 0.5-3 h. The maximal reduction of extracellular DA (by 29%) was observed for 2-2.5 h. Extracellular DA was reduced (21%) by 20 but not by 2 micrograms/kg ceruletide. DOPAC and HVA did not change at any dose of ceruletide. We also demonstrated that bilateral subdiaphragmatic vagotomy blocked this inhibitory effect of ceruletide on DA release. These findings indicate that peripherally administered ceruletide suppresses endogenous DA release via the vagal afferent system.

Subchronic cocaine treatment enhances cocaine-induced dopamine efflux, studied by in vivo intracerebral dialysis.

Repeated administration of cocaine in animals results in behavioral sensitization. In order to investigate the neurochemical mechanism underlying such behavioral sensitization, we designed the following two experiments. In both experiments, rats were pretreated with cocaine (20 mg/kg i.p.) or saline, once daily for 14 consecutive days. Exp. 1: 7 days after withdrawal from the drug, the stereotyped behavioral response to a challenge of cocaine (20 mg/kg i.p.) was measured. Exp. 2: 7 days after withdrawal from the drug, we measured extracellular dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) after the challenge administration of cocaine using an in vivo intracerebral dialysis technique. The rats pretreated with cocaine (20 mg/kg i.p.) exhibited behavioral augmentation in response to a challenge of cocaine. The challenge administration of cocaine caused an increase in DA and a decrease in DOPAC. The DA level in the striatal perfusates of the cocaine-pretreated rats was significantly greater than that in the saline-pretreated rats. These results suggest that the increased extracellular DA concentration in the striatum plays an important role in the cocaine-induced behavioral sensitization.

Effect of MK-801 on endogenous dopamine release in vivo.

The effect of MK-801 on striatal dopamine (DA) release was investigated by using an in vivo microdialysis technique in the freely moving rat. Systemic injection of MK-801 (0.25, 0.5, 1, 2 mg/kg, i.p.) reduced the extracellular level of DA significantly and produced no change in the level of 3,4-dihydroxyphenylacetic acid. The behavioral observation, recorded simultaneously, revealed that MK-801, with smaller doses, produced ipsilateral circling toward the side with the dialysis probe. At larger doses, MK-801 predominantly evoked ataxia. These findings indicate that the behavioral effect of MK-801 may not be mediated via the release of DA.

Serotonin1A receptor agonists induce Fos protein expression in the locus coeruleus of the conscious rat.

The azapirones, which are partial agonists of the serotonin (5-HT)1A receptor, possess anxiolytic activity. These agents may act at the pre- or postsynaptic 5-HT1A receptors, and involve the noradrenergic system. To determine whether these drugs activate noradrenergic neurons via 5-HT1A receptors, we have evaluated the expression of the immediate early gene c-fos in the locus coeruleus. Tandospirone and ipsapirone each induced expression of Fos protein in the noradrenergic neurons of the locus coeruleus of conscious rats. This effect was reversed by pretreatment with (+)-WAY100135, a specific 5-HT1A antagonist. These results clearly demonstrate that azapirones activate noradrenergic neurons via 5-HT1A receptors.

Enhanced extracellular dopamine level may be the fundamental neuropharmacological basis of cross-behavioral sensitization between methamphetamine and cocaine--an in vivo dialysis study in freely moving rats.

Intracerebral dialysis was used to study the mechanism underlying cross-behavioral sensitization between methamphetamine (MAP) and cocaine. The challenge injection of cocaine caused a significantly greater increase in striatal perfusate dopamine (DA) levels in MAP-pretreated rats than in saline-pretreated rats. Similarly, the challenge injection of MAP caused a significantly greater increase in extracellular DA levels in cocaine-pretreated rats than in control rats. These results suggest that an enhancement in striatal DA efflux may play an important role in cross-behavioral sensitization between MAP and cocaine.

Propranolol attenuates haloperidol-induced Fos expression in discrete regions of rat brain: possible brain regions responsible for akathisia.

Neuroleptics induce several extra-pyramidal side effects, such as akathisia, acute dystonia and parkinsonism. Although recently developed atypical neuroleptics ameliorate some of these side effects, akathisia remains a common and severely distressing adverse reaction. Several drugs are reported to be of clinical use for the pharmacological treatment of akathisia. In particular, the beta-adrenoceptor blocker, propranolol, has been widely used for the treatment of akathisia, but it does not ameliorate other extra-pyramidal side effects. To identify the neural substrates of akathisia, we investigated the effects of propranolol on haloperidol-induced Fos expression in rat brain. Haloperidol (1 mg/kg) induced Fos-positive nuclei in several regions of the brain, including the cingulate cortex area 3, piriform cortex nucleus accumbens, caudate-putamen, ventral lateral septum and parietal cortex. Pretreatment with propranolol (5 mg/kg) reduced the number of Fos-positive nuclei in the cingulate cortex area 3, the piriform cortex and area 1 of the parietal cortex. Injection of vehicle by itself tended to increase Fos expression in the cingulate cortex area 3 and the piriform cortex. Considering the functions of these brain regions, we speculate that the most plausible neural framework for haloperidol-induced akathisia involves area I of the parietal cortex, but possible roles for the cingulate cortex area 3 and the piriform cortex cannot be ruled out.

Co-administration of either a selective D1 or D2 dopamine antagonist with methamphetamine prevents methamphetamine-induced behavioral sensitization and neurochemical change, studied by in vivo intracerebral dialysis.

Repeated administration of amphetamine or methamphetamine (MAP) causes behavioral sensitization in animals. Recently, several studies have revealed that in vivo release of dopamine from presynaptic nerve terminals of mesotelencephalic dopamine neurons is enhanced when sensitized animals are rechallenged with a psychostimulant. The present study investigated the effect of co-administration of SCH 23390 (a selective D1 dopamine receptor antagonist) or YM-09151-2 (a selective D2 dopamine receptor antagonist) prior to each MAP injection for 14 days on dopamine efflux in the striatal perfusates using in vivo dialysis. After 3 months drug abstinence, MAP challenge alone produced augmented stereotypy in the MAP group, but not in the control, the SCH 23390 + MAP or the YM-09151-2 + MAP group. In parallel with this behavioral observation, the degree to which dopamine efflux increased following the MAP challenge was significantly greater in the MAP group than that in the control, SCH 23390 + MAP group and the YM-09151-2 + MAP groups. While dopamine efflux after MAP challenge did not differ between the control and the YM-09151-2 + MAP group, it was greater in the SCH 23390 + MAP group than the control group. These results indicate that both D1 and D2 dopamine receptors play a role in the formation of behavioral sensitization, but with different mechanisms.

Alterations of calmodulin and its mRNA in rat brain after acute and chronic administration of methamphetamine.

The effect of acute and chronic administration of methamphetamine (METH) on the levels of calmodulin (CaM) and its mRNAs has been investigated in rat brain using antisense oligonucleotides to three distinct rat CaM genes (CaM I, CaM II, CaM III). CaM I mRNA was reduced in the striatum and nucleus accumbens within 2 h of acute administration of 4 mg/kg METH, but returned to the control level by 6 h. The CaM content in both the cytosolic and membrane fractions of the striatum was reduced 0.5, 2, and 6 h after acute administration of METH. In the chronic experiments, rats were treated with either 4 mg/kg METH or saline once daily for 14 days. This was followed by a withdrawal period of 28 days, and thereafter, the animals were challenged with either METH (4 mg/kg, i.p.) or saline. All the animals were decapitated 6 h after this injection. There were four treatment groups: METH-METH (MM); METH-saline (MS); saline-METH (SM); and saline-saline (SS). There was a significant decrease in the mRNA for CaM I and CaM II in the striatum, and CaM II and CaM III in the nucleus accumbens in the MS group and the MS and MM groups, respectively, when compared to the SS group. The CaM content in the striatal membrane fraction decreased in both the SM and MS groups but not in the MM group. In contrast, the CaM content in the membrane fraction of the mesolimbic area showed a significant increase in the MM group. The CaM content in the cytosolic fraction of these brain areas decreased in both the SM and MM groups. The total CaM decreased significantly in the SM and MM groups of the striatum, but increased significantly in the MM group of the mesolimbic area. The mRNA for CaM I and CaM III decreased significantly in the MM group, and in the SM and MM groups, in the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA), respectively. The CaM content in both the cytosolic and membrane fractions and total CaM content of the SN/VTA decreased significantly in the SM, MS and MM group as compared with the SS group. In the medial prefrontal cortex and hippocampus the significant increase of CaM content in the membrane fraction of the MM group was also found, but neither the CaM content in the cytosol fraction nor total CaM content changed. These results suggest that chronic METH administration leads to a translocation of CaM from the cytosolic to membrane fractions; these may underlie METH-induced behavioral sensitization.

Enhanced stress-induced dopamine release in the prefrontal cortex of amphetamine-sensitized rats.

This study examined the extent to which chronic d-amphetamine administration sensitizes animals to some behavioral and neurochemical effects of foot shock stress. Rats received daily injections of saline for 14 days or d-amphetamine (2 mg/kg 7 days and 4 mg/kg 7 days). After a 7 day drug abstinent period, extracellular dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid concentrations were measured in the medial prefrontal cortex using in vivo microdialysis in freely moving rats. The behavioral responses to mild foot shock stress were enhanced in the d-amphetamine-pretreated subjects. Concomitant with this behavioral sensitization, d-amphetamine-pretreated subjects showed greater stress-induced increases in extracellular dopamine in the medial prefrontal cortex than in controls. d-Amphetamine (2 mg/kg)-induced stereotyped behavior was also enhanced in the amphetamine-pretreated animals compared to controls; however, d-amphetamine-induced increases in extracellular dopamine in the medial prefrontal cortex were not enhanced in the amphetamine-pretreated group. These results suggest that the mesocortical dopaminergic system is involved in cross-sensitization between d-amphetamine and stress, but not in d-amphetamine-induced behavioral sensitization.

M100907, a selective 5-HT(2A) receptor antagonist, attenuates phencyclidine-induced Fos expression in discrete regions of rat brain.

5-HT and dopamine receptor antagonists have become widely used as atypical antipsychotics. Although 5-HT(2A) receptor antagonistic activity is thought to contribute to the atypical aspects of these agents, the precise mechanism remains unknown. M100907 (R(+)-alpha(2,3-dimethoxyphenyl)-1-[2(4-fluorophenyl)ethyl)]-4-piperidine -methanol), a selective 5-HT(2A) receptor antagonist, is reported to attenuate phencyclidine (PCP)-induced locomotion in rodents. For the purpose of identifying regions in which M100907 exerts its effect, we investigated the effects of M100907 on PCP-induced Fos expression in rat brain. PCP (5 mg/kg, subcutaneously, s.c.) induced Fos expression in the cingulate cortex area 3, the agranular insular cortex, the piriform cortex, the nucleus accumbens, the anterior paraventricular thalamic nucleus and the ventral lateral septal nucleus. Pretreatment with M100907 (0.5 mg/kg, s.c.) attenuated Fos expression induced by PCP in the nucleus accumbens core, the shell, the agranular insular cortex and the piriform cortex. M100907 did not induce Fos expression in any of the regions investigated including the dorsolateral caudate/putamen when given alone. These results indicate that 5-HT(2A) receptor antagonism attenuates Fos expression in a regionally specific manner in rat brain in the PCP model of psychosis.

Effects of subchronic lithium chloride treatment on G-protein subunits (Golf, Ggamma7) and adenylyl cyclase expressed specifically in the rat striatum.

Lithium salt has been widely used as a treatment for mania, but the mechanism of its effect remains unknown. Previously, by studying c-fos expression, we showed that the striatum was a possible target region for the antimanic effects of lithium salt. The present study focused on the effect of subchronic lithium chloride treatment on G-proteins (Golf, Ggamma7) and adenylyl cyclase type V, which are expressed specifically in the rat striatum. Subchronic lithium chloride treatment significantly increased the level of Golf protein, a stimulant alpha-subunit of G-protein, by 53.5% (P<0.01), but the levels of Ggamma7 and adenylyl cyclase type V did not change. This increased level of Golf protein was found after 2 weeks of lithium chloride treatment, but not after 1 week, and the level returned to the basal level 1 week after withdrawal of lithium chloride. This result suggests that the level of Golf protein increases to compensate for the suppression of the adenylyl cyclase system by lithium, and that this increase may account for the "rebound" phenomenon, which is the relapse observed after abrupt discontinuation of lithium salt treatment.

Relapse of paranoid psychotic state in methamphetamine model of schizophrenia.

The study of the clinical course of methamphetamine (MAP) psychosis yields insights into the biological aspect of the relapse of the paranoid psychotic state with hallucination in schizophrenia. A series of MAP psychosis studies in Japan conducted over a period of more than four decades revealed three types of clinical courses of MAP psychosis after discontinuation of MAP: transient type, prolonged type, and persistent type. Identification of the latter two indicates a lasting change in the brain that produces and maintains a schizophrenia-like paranoid psychotic state without MAP. The characteristic course seen in the transient type is acute recurrence of the psychotic state after a long remission period, almost identical to the initial episode, due to reuse of MAP or to psychological stressors. Such lasting vulnerability of the brain to schizophrenia-like psychotic symptoms may be caused by a lasting sensitization of the brain to the psychotogenic action of MAP resulting from its chronic abuse. Experimental studies using animals sensitized to MAP-induced stereotypy suggest that lasting enhancement of MAP-induced dopamine release in the striatum and nucleus accumbens is related to the development and expression of brain vulnerability to schizophrenic symptoms.

A low dose of lithium chloride selectively induces Fos protein in the central nucleus of the amygdala of rat brain.

1. Lithium is a very effective treatment for mood disorders. To elucidate the neural substrates of the mood stabilizing actions of lithium, in the present study the authors investigated the effects of a low dose of lithium on regional expression of Fos protein. 2. The administrations of a high dose of lithium chloride (100 mg/kg) induced Fos in widespread areas of the rat brain. In contrast, administration of a low dose of lithium chloride, equivalent to a therapeutic dose in humans, induced Fos only in the central nucleus of the amygdala. 3. These results demonstrate that the central nucleus of the amygdala plays important role in the neural framework that is responsible for the mood-stabilizing effect of lithium.