In vitro alteration of the subcellular distribution of 3H-reserpine in the rat forebrain by delta 9-tetrahydrocannabinol.
delta 9-Tetrahydrocannabinol (delta 9-THC) has been reported to attenuate both reserpine-induced serotonin depletion and reserpine-induced hypothermia. We have observed that delta 9-THC preincubation led to a dose-responsive increase in the amount of 3H-reserpine bound to a crude mitochondrial fraction of rat forebrain. The experiments reported here further characterize this phenomenon. Preincubation with delta 9-THC produced a shift in the localization of 3H-reserpine from the incubation medium and the microsomal supernatant (decrease of 66%) to the crude mitochondrial (CM) pellet (increase of 154%). The CM pellet was subfractionated both by differential centrifugation after osmotic shock and by layering on a five-step discontinuous sucrose gradient and centrifuging at 80,000 x g. Osmotic shock with 0.032 M sucrose and centrifugation revealed that the delta 9-THC-induced increase in 3H-reserpine was contained in both the synaptic vesicle fraction (247%) and the fraction containing myelin, ruptured synaptosomes and mitochondria (324%). Separating the CM fraction into five component parts showed that delta 9-THC increased the 3H-reserpine bound by about 275% in the three fractions containing myelin, membrane fragments or mitochondria. Even more dramatic increases (greater than 1000%) were observed in the two fractions containing cholinergic and non-cholinergic nerve endings. In addition, we have determined that many other drugs which are believed to have membrane mediated mechanisms have no effect on the amount of 3H-reserpine bound to the crude mitochondrial fraction. Although other possibilities exist, these data support the hypothesis that delta 9-THC retards the action of reserpine by altering the normal distribution of reserpine in various membrane components of the rat brain.
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002186:Cannabinoids / Q000494:pharmacology; D013759:Dronabinol / Q000378:metabolism / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012110:Reserpine / Q000378:metabolism* / Q000494:pharmacology
D002186:Cannabinoids; D013759:Dronabinol; D012110:Reserpine