Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of pube rty. However, the mechanism controlling the pubertal increase in LHRH relea se is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state i n the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Re cent studies suggest that during the prepubertal period an inhibitory neuro nal system suppresses LHRH release and that during the subsequent maturatio n of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, gamma -aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restric ting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, wh ich contributes to the increase in pubertal LHRH release. In this review, d evelopmental changes in several neurotransmitter systems controlling pulsat ile LHRH release are extensively reviewed.