Excitatory and inhibitory effects of prolactin release activated by nerve stimulation in rat anterior pituitary.
BACKGROUND
A series of studies showed the presence of substantial amount of nerve fibers and their close relationship with the anterior pituitary gland cells. Our previous studies have suggested that aside from the classical theory of humoral regulation, the rat anterior pituitary has direct neural regulation on adrenocorticotropic hormone release. In rat anterior pituitary, typical synapses are found on every type of the hormone-secreting cells, many on lactotrophs. The present study was aimed at investigating the physiological significance of this synaptic relationship on prolactin release.


METHODS
The anterior pituitary of rat was sliced and stimulated with electrical field in a self-designed perfusion chamber. The perfusate was continuously collected in aliquots and measured by radioimmunoassay for prolactin levels. After statistic analysis, differences of prolactin concentrations within and between groups were outlined.


RESULTS
The results showed that stimulation at frequency of 2 Hz caused a quick enhancement of prolactin release, when stimulated at 10 Hz, prolactin release was found to be inhibited which came slower and lasted longer. The effect of nerve stimulation on prolactin release is diphasic and frequency dependent.


CONCLUSIONS
The present in vitro study offers the first physiological evidence that stimulation of nerve fibers can affect prolactin release in rat anterior pituitary. Low frequency stimulation enhances prolactin release and high frequency mainly inhibits it.
Zhang
Ping
P
Institute of Neurosciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China. appleping@sjtu.edu.cn
Liu
Ling
L
Xie
Cong-Jun
CJ
Wang
Kai-Hu
KH
Gao
Li-Zhi
LZ
Ju
Gong
G
D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D010903:Pituitary Gland, Anterior / Q000294:innervation / Q000378:metabolism* / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology
D013779:Tetrodotoxin; D011388:Prolactin