piperidines and setoperone

Topics: Brain; Butyrophenones; Humans; Isoxazoles; Piperidines; Pyrimidinones; Randomized Controlled Trials as Topic; Receptors, Serotonin; Risperidone; Ritanserin; Schizophrenia; Schizophrenic Psychology; Serotonin Antagonists

In vivo occupancy by typical or atypical antipsychotic drugs of dopamine D-1, D-2 and serotonin (5-HT)2 receptors in the membranes and slices of the rat brain was measured using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), an irreversible antagonist at these receptor sites. In the membranes, the occupancy of D-1 receptors in the striatum by all tested drugs except cis-flupenthixol was minimal. Typical antipsychotic drugs such as chlorpromazine (10 mg/kg), haloperidol (1 mg/kg), cis-flupenthixol (1 mg/kg) and zotepine (5 mg/kg) occupied predominantly D-2 receptors in the striatum. Among atypical antipsychotic drugs, sulpiride (30 mg/kg) and amperozide (1 mg/kg) had no effect on the EEDQ-induced reduction in D-1, D-2 or 5-HT2 receptors, whereas clozapine (10 mg/kg), fluperlapine (10 mg/kg), risperidone (1 mg/kg), setoperone (0.25 mg/kg) and ORG 5222 (0.25 mg/kg) occupied mainly 5-HT2 receptors in the frontal cortex. In the slices, the occupancy by all tested drugs of D-1 receptors in the striatum, nucleus accumbens and substantia nigra was minimal with the exception of clozapine which showed about 30% occupancy in the substantia nigra. Typical antipsychotic drugs, chlorpomazine (10 mg/kg) and haloperidol (1 mg/kg) occupied predominantly D-2 receptors in the striatum and the nucleus accumbens. On the other hand, atypical antipsychotic drugs, clozapine (10 mg/kg) and risperidone (1 mg/kg), occupied mainly 5-HT2 receptors in the frontal cortex. These results suggest that there is a certain group of atypical antipsychotic drugs characterized by high occupancy of 5-HT2 receptors and low or minimum occupancy of D-2 receptors. These characteristics may be relevant to their weak potency in producing extrapyramidal side effects in man or catalepsy in rodents. Although we could find no clear regional differences in receptor occupancies by these antipsychotic drugs, further study are needed to elucidate this issue.

Topics: Animals; Antipsychotic Agents; Autoradiography; Brain; Chlorpromazine; Clozapine; Dibenzothiepins; Flupenthixol; Haloperidol; In Vitro Techniques; Isoxazoles; Male; Piperidines; Pyrimidinones; Rats; Rats, Wistar; Receptors, Dopamine; Receptors, Serotonin; Risperidone

LY53857, spiperone, ketanserin, and setoperone were potent and competitive 5-HT2-receptor antagonists in the rat jugular vein with equivalent affinities at 5-HT2 receptors. In the rat jugular vein, ritanserin blocked 5-HT2-mediated contractile responses with a depression of the maximum response in concentrations greater than 3 X 10(-10) M. Ketanserin, spiperone, ritanserin, and setoperone were also alpha 1-adrenergic receptor antagonists, although affinity at alpha 1-adrenergic receptors was less for ritanserin and setoperone than for ketanserin or spiperone. Of the 5-HT2-receptor antagonists examined, LY53857 was the most selective with respect to alpha 1-adrenergic receptor affinity, showing 250,000-fold selectivity as an antagonist at 5-HT2 receptors. The possibility that the dual properties of 5-HT2- and alpha 1-receptor blockade confer greater antihypertensive efficacy than alpha 1-receptor blockade alone was also examined in vivo. However, acute administration of LY53857 at doses sufficient to abolish 5-HT2-receptor activation did not enhance blood pressure reduction produced by the alpha-adrenergic receptor antagonist phentolamine in normotensive or spontaneously hypertensive rats. These data argue against an important role for 5-HT2 receptors in blood pressure regulation even in combination with alpha-adrenergic receptor blockade.

Topics: Adrenergic alpha-Antagonists; Animals; Blood Pressure; Ergolines; Ketanserin; Male; Muscle Contraction; Muscle, Smooth, Vascular; Phentolamine; Piperidines; Pyrimidinones; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Receptors, Adrenergic, alpha; Receptors, Serotonin; Ritanserin; Serotonin Antagonists; Spiperone

Topics: Animals; Brain; Corpus Striatum; Frontal Lobe; Male; Piperidines; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Dopamine D2; Receptors, Serotonin; Ritanserin; Serotonin Antagonists

Rats were chronically treated with setoperone, a mixed serotonin and dopamine antagonist. Alterations in serotonin-S2 and dopamine-D2 receptors in the brain and changes in behavioural responses to tryptamine and apomorphine were studied along with duration of treatment and drug withdrawal. As with neuroleptics, behavioural supersensitivity to apomorphine and increase in the number of striatal dopamine-D2 receptor sites were apparent after 2 days setoperone treatment, both effects were maximal with 14 days treatment and were maintained over more than 20 days drug withdrawal. In contrast to the changes in the dopaminergic system, the rats showed a decreased response to tryptamine and serotonin-S2 receptor sites in the frontal cortex were significantly reduced in numbers. Both effects developed in parallel over 14 days treatment and extinguished over 10 days drug withdrawal. KD-values of radioligand binding to dopamine-D2 and serotonin-S2 receptor sites were unchanged by the setoperone treatment. The concomitant development and extinction of the in vivo and in vitro effects suggests a causal relationship between them. Chronic treatment with a selective histamine-H1 antagonist (levocabastine) or the tranquilizer diazepam did not affect dopamine-D2 or serotonin-S2 receptor sites. These observations demonstrate that in contrast to the receptor regulation theory, serotonin-S2 receptors are down regulated following persistent receptor blockade. Implications for the clinical use of serotonin antagonists and possible molecular mechanisms involved in the receptor regulation have been discussed.

Topics: Animals; Apomorphine; Behavior, Animal; Corpus Striatum; Diazepam; Dopamine Antagonists; Frontal Lobe; Gene Expression Regulation; Ketanserin; Male; Models, Biological; Piperidines; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Serotonin; Serotonin Antagonists; Tryptamines

Ritanserin is a potent and selective serotonin-S2 antagonist which slowly dissociates from the receptor sites, while setoperone has potent serotonin and moderate dopamine antagonistic properties and dissociates rapidly from the receptor sites. Acute administration of ritanserin (1-10 mg/kg) produced a non-competitive inhibition of 3H-ketanserin binding, measured ex vivo in washed frontal cortex membranes, which lasted for 12 h. This is in accordance with the slow dissociation of the drug from the receptor sites. Setoperone (1-10 mg/kg orally) also produced a partially non-competitive inhibition of 3H-ketanserin binding in washed membranes, which is unlike its rapid dissociation. In contrast, there was no inhibition of dopamine receptor binding in washed striatal membranes. Chronic oral administration of 10 mg/kg X day of the drugs significantly reduced the Bmax values of 3H-ketanserin, without changing the KD value when drug-free periods were longer than 1 day. The maximum reduction following 25 days' treatment with 14 mg/kg ritanserin was 50% at 1 day drug-free; the Bmax values gradually returned to the control value in about 12 days. The receptor half-life was calculated to be 3.5 days and the receptor synthesis rate 4 fmoles/mg tissue X day. Ritanserin treatment did not alter radioligand binding to serotonin-S1, alpha 1-, alpha 2- and beta-adrenergic, dopamine-D2, benzodiazepine and substance P sites. Chronic treatment with setoperone at 10 mg/kg X day, orally, significantly reduced the Bmax value of 3H-ketanserin binding in frontal cortex but treatment with 1 mg/kg X day did not. In contrast, a dose-dependent increase in the number of striatal dopamine-D2 sites was observed, in accordance with the moderate dopamine-antagonistic properties of setoperone. Dopamine-D2 receptor up regulation up to 150% of control values, was maintained at the same level for 9 days, it started to decline 12 days after stopping drug treatment. Following chronic treatment and drug withdrawal for more than 1 day, ritanserin and setoperone levels in whole brain homogenates were below detection level (less than 1 ng/g). The similar reduction in the Bmax values of 3H-ketanserin binding following chronic treatment with the rapidly dissociating setoperone and the slowly dissociating ritanserin, the absence of effect on the KD value, the slow reappearance of the receptor sites and the opposite effect on serotonin-S2 and dopamine-D2 receptors with setoperone suggest that real seroto

Topics: Animals; Brain; Corpus Striatum; Frontal Lobe; Ketanserin; Male; Piperidines; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Dopamine D2; Receptors, Neurotransmitter; Receptors, Serotonin; Ritanserin