Neuroleptics and neuroendocrine function.

Neuroleptics have been developed primarily to treat psychoses, but they have become invaluable research tools. Because of their selective action on DA receptors, neuroleptics are commonly employed to study the function and regulation of DA neurotransmission. The relationship between the antipsychotic efficacy and the DA receptor affinity of the various neuroleptic drugs has lead to the development of new DA antagonists in hopes of discovering novel antipsychotic agents. This approach has produced interesting new compounds selective for the DA receptor subtypes. The use of DA receptor antagonism as a measure of the potential antipsychotic efficacy of a compound will undoubtedly change as the mechanisms behind the antipsychotic actions of neuroleptics become better understood. Although endocrine side effects of neuroleptic administration are undesired in the clinic, they have provided insight into the neuroendocrine regulation of pituitary hormones. Through the use of neuroleptics, DA neurons in the hypothalamus have been shown to play a role in the regulation of prolactin, GH, and TSH secretion. The ability of DA to act at the pituitary and thereby inhibit the secretion of these three hormones suggests that other regulatory factors must provide the specificity needed for the differential secretion of the individual hormones during varying physiological states. Future research will certainly explore the interactions of DA and these regulatory factors at the pituitary. The role of DA in neuroendocrine regulation is not limited to the pituitary. The presence of DA neurons within the hypothalamus offers the possibility of DA regulation of hypothalamic neurosecretory activity.