Effects of delta-9-tetrahydrocannabinol on reproductive neuroendocrine function in the female: animal studies

The rat experimental model has been utilized to demonstrate pronounced suppressive effects of THC on the secretion of both LH and PRL, a point of considerable interest since the tonic secretions of these two hormones are regulated in opposite fashions, that of LH requiring active stimulation, and that of PRL, continued inhibition. Moreover, both the tonic and surge modes of secretion of both hormones are inhibited or completely blocked by THC action even though these different secretory modes are presumed to be governed by different CNS regulatory mechanisms. The most direct explanation for this broad inhibitory capability of THC would be direct inhibitory action on the pituitary cells secreting LH and PRL. However, experimental evidence drawn from the rat model, consistent with that from other species, provides no support for the possibility of direct pituitary inhibition of significant consequence. Instead, the evidence strongly favors the hypothesis that THC exerts its neuroendocrine action centrally and thereby influences pituitary function through alterations in the release of hypothalamic hormones into the hypophysial portal circulation. With the evidence favoring a central neuroendocrine mechanism for THC action, the rat model becomes particularly valuable because of the enormous body of information already available regarding neuroendocrine function in that species. Initial experiments with the rat have failed to provide evidence supporting the possibility of direct THC action on the hypothalamic neurosecretory neurons terminating in the median eminence.(ABSTRACT TRUNCATED AT 250 WORDS)