Gamma-aminobutyric acid controls the mouse hypothalamic-pituitary-testicular response to the presence of female.

The role of gamma-aminobutyric acid (GABA) in the control of plasma testosterone was studied on male mice of inbred strains (CBA/Lac, A/He and BALB/c) exposed to a sexually receptive female in the same cage but separated by a partition. Within 40 minutes, testosterone levels in plasma increased 1.5-3.5 times depending upon the mouse genotype. This process could be completely blocked if GABA accumulation was induced by pretreatment with the GABA transaminase inhibitor, aminooxyacetic acid (AOAA), or by emotional stress induced by 40 min of restraint. Neither bicuculline-induced blockade of GABA receptors nor a decrease of GABA concentration induced by prior administration of thiosemicarbazide (an inhibitor of glutamate decarboxylase), affected the increase of plasma testosterone that occurred in response to presentation of a receptive female. However, at sexual arousal, the bicuculline blockade of GABA receptors significantly reduced the inhibitory effects of both AOAA administration and emotional stress on plasma testosterone levels. We conclude that the inhibitory effect of emotional stress on female-induced activation of testicular endocrine function is mediated, at least in part, via activation of bicuculline-sensitive receptors.