Hypothermic effects of intraventricular and intravenous administration of cannabinoids in intact and brainstem transected cats
Schmeling, W.T.; Hosko, M.J.
Neuropharmacology 19(6): 567-573
ISSN/ISBN: 0028-3908 PMID: 7402446 Accession: 005605639
.DELTA.9-Tetrahydrocannabinol (.DELTA.9-THC, 500 .mu.g in 40 .mu.l), and the synthetic cannabinoid Dimethylheptylpuran (DMHP, 75 .mu.g in 6.0 .mu.l) were injected into ventricles III or IV of chronically implanted unanesthetized cats to determine the effect on body temperature. The hypothermia induced by administration of .DELTA.9-THC into ventricle IV was faster in onset and reached a greater maximum than that induced by ventricle III administration. .DELTA.9-THC 500 .mu.g, produced significantly less hypothermia than interventricular microinjection. Administration of .DELTA.9-THC (2 mg/kg i.v.) to animals with a midcollicular transection produced significant decreases in blood pressure, heart rate and body temperature when compared to animals receiving vehicle alone. Cats transected at C-1 were used to determine the rate at which body temperature was lost in animals unable to regulate temperature. .DELTA.9-THC had no effect in these preparations; direct peripheral mechanisms have little or not role in .DELTA.9-THC induced hypothermia. .DELTA.9-THC had little effect on blood pressure or heart rate in C-1 transected animals. The caudal brain stem may be a site of action for the hypothermic effect of the cannabinoids.