POSSIBLE ROLE OF THE CYTOCHROME P450-LINKED MONOOXYGENASE SYSTEM IN PREVENTING DELTA-(9)-TETRAHYDROCANNABINOL-INDUCED STIMULATION OF TUBEROINFUNDIBULAR DOPAMINERGIC ACTIVITY IN FEMALE RATS

The administration of delta(9)-tetrahydrocannabinol (THC) or related cannabinoids markedly affected neurobehavioral and neuroendocrine indices in male rodents but usually failed to affect those indices in females. We examined whether inhibition of the cytochrome P450-linked monooxygenase system in female rats is able to elicit the effects of THC on one of the most characteristic targets of cannabinoid action, tuberoinfundibular dopaminergic neurons, whose activity is known to increase after cannabinoid exposure in males. It was found that the administration of THC to ovariectomized rats acutely replaced with estradiol (to discard problems derived from differences in the estrogenic status) did not affect either dopamine and L-3,4-dihydroxyphenylacetic acid (DOPAC) contents and tyrosine hydroxylase activity in the medial basal hypothalamus or the density of D2-dopaminergic receptors in the anterior pituitary. However, the administration of THC to estrogen-replaced ovariectomized rats that had been pretreated with two separately administered inhibitors of cytochrome P450, piperonyl butoxide or metyrapone, significantly increased DOPAC content in the medial basal hypothalamus, with no changes in the other parameters. Collectively, these results indicate that the metabolism of THC to inactive compounds might play a protective role in females. counteracting the effects of this cannabinoid on tuberoinfundibular dopaminergic activity because pharmacological inhibition of cytochrome P450-linked monooxygenase system elicited a significant stimulation of these neurons by THC.