The central anti-serotonin activity of zotepine, a new neuroleptic, in rats

Zotepine-induced catatonia as a precursor in the progression to neuroleptic malignant syndrome

A 39-year-old man with schizophrenia developed severe catatonia, hyperthermia, muscle rigidity, tachycardia, leukocytosis, and elevated muscle enzyme levels while receiving zotepine therapy. Neuroleptic malignant syndrome (NMS) was diagnosed. After withdrawal of zotepine therapy, transfer to a neurologic intensive care unit, provision of supportive care, and administration of adjunctive bromocriptine therapy, the patient's fever and catatonia subsided. Biochemical irregularities spontaneously returned to normal with no complications. Antipsychotic therapy was restarted with risperidone 12 days after the patient's NMS resolved. After more than 1 year of follow-up, he experienced no adverse events. A recent decrease in mortality from NMS is related to increased awareness of this disorder, but not to treatment with specific agents. Clinicians need to recognize NMS early; although rare, it is a potentially fatal complication of antipsychotic treatment.

Two case studies of hypothermia induced by an increased dosage of zotepine in a combination therapy

The purpose of the present paper was to remind physicians that hypothermia is a possible side-effect of combining zotepine, valproate,and benzodiazepine. Two cases of hypothermia occurred after combining the use of zotepine, valproate, and benzodiazepine. The valproate was under therapeutic blood level when zotepine dosage was raised to 200 mg/day, and hypothermia occurred. The dosage of zotepine might constitute a positive correlation with hypothermia. The combination of zotepine, valproate or benzodiazepine may cause hypothermia as a side-effect.

Genetic association analysis of 5-HT(6) receptor gene polymorphism (267C/T) with tardive dyskinesia

Possible involvement of serotonergic (5-hydroxytryptamine: 5-HT) receptors in the pathophysiology of tardive dyskinesia (TD) has been suggested. In the present study, the relationship between the 5-HT(6) receptor gene (HTR6) polymorphisms and TD was studied in 173 Japanese patients with schizophrenia. The 267C/T allele of HTR6 was genotyped using PCR amplification followed by endonuclease digestion. The patients with the three 267C/T genotypes showed no significant difference in gender, age, duration of illness, or current antipsychotic dose. In addition, there were no significant differences in total AIMS scores among patients with the three genotypes. Moreover, no significant differences in genotypes and allele frequencies were observed between subjects with and without TD. These results suggest that the 267C/T polymorphism of HTR6 does not confer increased susceptibility to TD.

Seroquel: electrophysiological profile of a potential atypical antipsychotic

Extracellular single unit recording techniques were employed to compare the effects of seroquel with the reference antipsychotic (AP) agents clozapine and haloperidol in electrophysiological tests that may predict AP activity. Seroquel and clozapine were differentially more active in reversing the inhibitory actions of d-amphetamine on mesolimbic (A10) than nigrostriatal (A9) dopamine (DA)-containing neurons, whereas haloperidol exhibited the opposite selectivity. In cell population studies, acute treatment with seroquel and clozapine selectively increased the number of spontaneously active A10 DA cells, which was found to correlate with the ability of both these drugs to cause depolarization inactivation (DI) of A10 DA cells following repeated (28 day) administration. This profile of activity was unlike that of haloperidol, which acutely caused a nonselective increase in the number of active A9 and A10 DA cells, associated with the ability of this agent to cause DI of both A9 and A10 DA cells after repeated treatment. Since DI of A10 DA cells may be correlated with AP efficacy whereas DI of A9 DA cells may predict the ability of an AP to cause extrapyramidal side effects (EPS) and tardive dyskinesia (TD), seroquel, like clozapine, may be an atypical AP with a reduced likelihood for producing EPS/TD.

Characterization of in vitro metabolites of the antipsychotic drug tiospirone by mass spectrometry

Metabolism of the antipsychotic drug tiospirone was studied in vitro with phenobarbital-induced rat liver microsomes. Metabolites were isolated and purified to homogeneity by high-performance liquid chromatography. It was possible to characterize the metabolites as trimethylsilyl (TMS) derivatives by gas chromatography/electron impact mass specrometry (GC/EIMS) so long as the sulfur was present in the reduced form. However, sulfoxide and sulfone analogs of tiospirone underwent reductive decomposition on the GC column. In addition, no molecular ions were observed in the EI spectra of these analogs. Desorption chemical ionization/mass spectrometry (DCI/MS) in the positive ion mode with methane as reagent gas successfully distinguished sulfoxides and sulfones from their parent sulfides. Protonated molecular ions were observed together with structurally significant fragment ions. Five microsomal metabolites of tiospirone were characterized by a combination of GC/EIMS and DCI/MS. From the structures of the metabolites three major pathways of metabolism were identified: N-dealkylation of the butyl side chain at the piperazinyl nitrogen, hydroxylation alpha to the glutarimidyl carbonyl at C-6 on the azaspirodecanedione ring, and sulfoxide formation on the benzisothiazole moiety.

Selective breeding for increased cholinergic function: increased serotonergic sensitivity

The effects of the serotonergic antagonist cyproheptadine and the agonist 1(m-chlorophenyl) piperazine (mCPP) on core body temperature, locomotor activity and operant responding for a water reward were determined in two lines of Sprague-Dawley rats selectively bred for differences in sensitivity to the anticholinesterase, diisopropyl fluorophosphate (DFP). Both cyproheptadine and mCPP induced a dose-dependent hypothermia that was significantly greater in the line of rat more sensitive to DFP (the Flinders Sensitive Line--FSL). On the other hand, the mild stimulant effects of cyproheptadine on operant responding and locomotor activity were similar in the two lines, whereas the marked inhibitory effects of mCPP on these two measures were significantly greater in the FSL rats. This study also confirmed that the FSL rats were significantly more sensitive to the hypothermic effects of oxotremorine, a muscarinic agonist, and showed that pretreatment with cyproheptadine reduced the hypothermic effects of oxotremorine to a similar extent in the two lines. These findings indicate that rats selectively bred for increased cholinergic function (FSL) also differ in their sensitivity to serotonergic agonists and antagonists, thereby extending the evidence for cholinergic-serotonergic interactions in the rat.

Acute effect of TRH, flunarizine, lithium and zotepine on amygdaloid kindled seizures induced with low-frequency stimulation

We assessed the acute effects of various drugs on amygdaloid kindled seizures induced with low-frequency stimulations. We used the number of stimulating pulses required for the induction of epileptic afterdischarge (pulse-number threshold; PNT) as an indicator of the seizure generating threshold and the duration of induced seizures (AD duration; ADD) as an indicator of the seizures. TRH increased the PNT without affecting the ADD at a high dose (1.2 mg/kg). Flunarizine decreased the PNT and ADD simultaneously at a high dose (50 mg/kg). Lithium increased the PNT without affecting the ADD at two doses (100 mg/kg, 200 mg/kg). Zotepine decreased the PNT without affecting the ADD at two doses (8 mg/kg, 16 mg/kg). We propose that the technique of low-frequency kindling is a useful experimental model in assessing the effects of antipsychotic or antiepileptic drugs on the excitability of the limbic regions.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Neuroleptic drugs and 5HT1 receptor: different potencies of various neuroleptic drugs on 5HT1 receptors in discrete regions of the rat brain

The potencies of various neuroleptic drugs (zotepine, chlorpromazine-HCl, haloperidol and spiperone) on serotonin1 (5HT1) receptors were examined in discrete rat brain regions using the radio receptor assay. The potencies of the neuroleptic drugs on 5HT1 receptors were clearly differentiated in the discrete brain regions: zotepine was the most potent in the frontal cortex, striatum and brain stem; spiperone was the most potent in the hippocampus. Furthermore, zotepine and chlorpromazine-HCl produced no great differences among the various regional 5HT1 receptors, while butyrophenones, haloperidol and spiperone showed remarkable differences. These findings demonstrate that the neuroleptic drugs can be differentiated according to their different affinities for regionally discrete 5HT1 receptors in the brain. This suggests that 5HT1 receptors may be able to be classified into two subtypes: the zotepine and chlorpromazine-HCl group having a high affinity for one subtype and butyrophenones a high affinity for the other.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents: II

This survey begins a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1978, but data from many earlier papers are also tabulated.