Neurotransmitters are the key of most neuronal functions; they are synthesized from presynaptic neurons and liberate their effect postsynaptically; not only neuronal functions are affected by neurotransmitters but also the functions of other organs are affected. Here; we try to investigate the effect of excitatory (glutamate and L-Arginine which is precursor of nitric oxide) and inhibitory (gamma amino butyric acid) neurotransmitters on male reproduction. These neurotransmitters were injected intramuscular in adult male rats every three days for two successive months (length of spermatogenic cycle); every 10 days blood samples and pituitaries were collected for hormonal assay (testosterone, gametogenic hormone and interstitial cell stimulating hormone) also, testes were collected for histopathological study. We found that glutamate and prolonged administration of L-Arginine was concomitant with elevation of both pituitary and serum interstitial cell stimulating hormone with decrease level of testosterone. On the contrary; gamma amino butyric acid administration lowered pituitary and serum interstitial cell stimulating hormone level as well as serum testosterone. Disturbance of hormonal level was accompanied by dramatic changes in testicular histology; these changes represented by peritubular edema, necrosis of spermatogenic cells and distortion of seminiferous tubules caused by glutamate. Rats whose testes received L-arginine showed sever necrosis, mild arrest of spermatogenesis while, testes received gamma amino butyric acid showed interstitial edema, degeneration of leydig cells, irregular of spermatogenic cycle and atrophy of some seminiferous tubules.