Neuroendocrine regulation of pulsatile luteinizing hormone release in the rat.

This review considers some of the neuroendocrine factors influencing pulsatile LH secretion. Such release is apparently due to the pulsatile discharge of LHRH from brain peptidergic neurons. This is a physiologically important event since a periodic rather than continuous input signal to the pituitary gland prevents it from becoming refractory to LHRH stimulation. Pulsatile secretion of LH, in the rat at least, does not appear to be regulated sloely by the medial basal hypothalamus. Central noradrenergic, cholinergic, dopaminergic, and serotoninergic systems are involved in influencing episodic LH release, presumably by affecting pulsatile LHRH secretion. Moreover, several hypothalamic as well as extrahypothalamic areas appear to play integral parts in controlling the rhythmic alterations in blood LH levels. These regions include the arcuate and suprachiasmatic nuclei, perisuprachiasmatic area, medial preoptic area, and midbrain dorsal raphe nucleus. Ovarian steroids also exert important influences on pulsatile LH relase, and greatly modify the response of this secretory system to neurotransmitters and stimuli from certain brain regions.