Study on the mechanism of the long-lasting antagonistic effect of caerulein on amphetamine-induced hyperactivity in rats

Effect of ceruletide on discriminated avoidance behavior in rats

To clarify the central action of peripherally administered ceruletide, we examined the effects of ceruletide and four different classes of neuroleptics, i.e. haloperidol, chlorpromazine, oxypertine and sulpiride, on the discriminated avoidance response (DAR) in rats. Ceruletide and sulpiride did not suppress the DAR over a broad range of doses, whereas other three neuroleptics caused a dose-related decrease in both avoidance and response rates. In addition, the combined administration of ceruletide (100 micrograms/kg s.c.) and neuroleptics at critical doses that suppress the DAR caused a significant reduction in the avoidance rate without affecting the response rate, compared with neuroleptics alone. These findings suggest that ceruletide influences the central dopaminergic system, potentiating the central effects of neuroleptics and producing the favorable therapeutic effects observed in the clinical trials.

Endogenous opiates: 1986

This is the ninth installment of our annual review of research involving the endogenous opiate peptides. It is restricted to the non-analgesic and behavioral studies of the opiate peptides published in 1986. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic processes; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; activity; sex, pregnancy, and development; and some other behaviors.

Bilateral subdiaphragmatic vagotomy does not prevent the behavioral effects of systematically administered ceruletide in mice

To clarify the vagal mediation of behavioral changes following systematically administered CCK-like peptides, we examined the effects of subcutaneously injected ceruletide on several behavioral parameters. Ceruletide at a dose of 100 micrograms/kg reduced the rates of spontaneous locomotor activity and rearing, and also inhibited methylphenidate- and methamphetamine-induced hyperactivity in both sham-operated and vagotomized mice to same extent, whereas bilateral subdiaphragmatic vagotomy attenuated these behavioral parameters. These results indicate that the ascending sensory pathway mediating a peripheral CCK-elicited signal may not be responsible for producing the behavioral effects of systematically administered CCK-like peptides.

A neuroendocrinological study of responders and non-responders to ceruletide treatment in chronic neuroleptic-resistant schizophrenia

To define the characteristics of chronic schizophrenic patients who had responded poorly to treatment with ceruletide, several neuroendocrinological tests were carried out in 5 responders and 5 non-responders. Both thyroid-stimulating hormone and prolactin responses to thyrotropin-releasing hormone stimulation were within normal ranges in all subjects. The luteinizing hormone response to luteinizing hormone-releasing hormone, was slightly weaker in non-responders. There were no differences in the insulin tolerance test between responders and non-responders. Unusually delayed or prolonged growth hormone response to arginine infusion was observed in non-responders. These findings suggest dysfunction of the hypothalamo-pituitary system, especially of the arcuate nucleus and its functionally related areas, in non-responders.