Effect of H2 receptor blockade upon hypothermic, cataleptogenic and antinociceptive action of prostacyclin (PGI)2 administered into the lateral rat brain ventricle.

Prostacyclin (PGI2) administered i.c.v. into the lateral rat brain ventricle in a dose of 1 and 10 micrograms causes hypothermia, catalepsy as well as a mild analgesic effect. Joint administration of PGI2 along with chloropromazine or morphine produces a greater cataleptic effect than that observed after application of neuroleptics and morphine alone. Cimetidine (CMT) (2 g/kg p.o.) administered 60 min before intraventricular PGI2 injection inhibits hypothermic and cataleptogenic action of the investigated prostaglandin. CMT blocks cataleptogenic effect of chloropromazine and morphine as well as the combination of these two substances with PGI2. CMT inhibits the cataleptogenic effect of haloperidol, but it does not block the catalepsy induced by joint administration of haloperidol and PGI2. CMT does not modify the analgesic action of PGI2. The results indicate that H2 receptors take part in some central pharmacological effects of PGI2 in rats.