Somatic afferent regulation of plasma luteinizing hormone and testosterone in anesthetized rats

The effects of cutaneous stimulation on plasma luteinizing hormone (LH) and testosterone were examined in adult male Wistar rats anesthetized with pentobarbital. Under the resting condition without somatic sensory stimulation, plasma LH and testosterone measured every 30 min between 1400 and 1730 h revealed no significant fluctuations. Nociceptive mechanical stimulation of bilateral hindpaws by pinching for 10 min significantly increased plasma LH and testosterone. Plasma LH was increased 30 and 60 min after stimulation, while plasma testosterone was increased 60-150 min after stimulation. However, innocuous mechanical stimulation of bilateral hindlimbs by brushing for 10 min did not significantly change either plasma LH or testosterone. These results indicate that, when emotional factors were eliminated by anesthetization, cutaneous nociceptive information led to the increased secretion of LH from the anterior pituitary, resulting in an increase in testosterone secretion from the testes into the plasma.