Nerve growth factor, tyrosine hydroxylase and apoptotic regulators in the testis of socially isolated mice: modulation by low-frequency electro-acupuncture.

Stress plays a detrimental role on male fertility, deregulating spermatogenesis and leading to poor sperm quality. Nerve growth factor (NGF), a major modulator of the stress response, the neuro-endocrine axis and sympathetic nervous system, is also an important auto/paracrine regulator of spermatogenesis. We previously demonstrated that modulation of NGF by sensory stimulation through low-frequency electroacupuncture (EA) could have a therapeutic value in female infertility, normalizing ovarian responsiveness to sympathetic input. In the present work we verify the hypothesis that EA could affect testis NGF system as well as regulators of spermatogenesis in a social isolation stress model. Adult male CD-1 mice were housed singularly for 60 days inducing impaired response of the HPA axis and the sympathetic nervous system. Control and isolated mice were then treated twice a week for four weeks with low-frequency EA at the acupoint St36. Testis NGF content was increased by EA in control and decreased in isolated mice. EA augment the phosphorilation of NGF receptor tyrosine-kinase-A and increased testicular content of the p75 neurotrophin receptor in isolated mice. The catecholamine rate-limiting enzyme tyrosine hydroxylase was increased by social isolation and diminished by EA in the testis of isolated mice, suggesting normalization of catecholaminergic activity. Concomitant to the NGF system modulation, EA counteract the isolation-induced testicular down-regulation of the anti-apoptotic protein Bcl-2, suggesting an action on spermatogenesis. Our data indicate that EA, most probably affecting the neuro-endocrine axis activity and/or the sympathetic tone, could affect the testicular homeostasis, counteracting the effect of stress on male fertility.