7TH STEVENSON LECTURE - BRAIN AMINES AND PITUITARY GONADOTROPIN-SECRETION

In conclusion it would appear that the brain monoamines may influence pituitary gonadotrophin secretion in a modulatory manner without being absolutely mandatory to the process. In a modulatory sense NE is stimulatory, 5-HT inhibitory, and DA practically neutral in influencing an ovulatory surge of LH in the proestrous or OEP rat. The responsiveness of neurons to either electrical stimulation or treatment with monoamines may be completely reversed with appropriate hormonal treatment such as estrogen after long-term ovariectomy. There are suggestions that the monoaminergic receptors may become supersensitive to their specific neurotransmitters when their presynaptic pathways are destroyed and (or) that much more of the transmitter may ordinarily be present than is needed to modulate the neuroendocrine effects. Reproduction is such an important function that provision for alternative neuroendocrine mechanisms to assure its success should not be a surprising achievement in the bodily economy.