The effect of testosterone administration on motor nucleus of the trigeminal nerve in immature of castrated male rat

The steroid hormones play a significant role on different target organs including the central and peripheral nervous system. It is known, that the androgens influence on motor neurons of muscles that directly involved in sexual activity. The masticator muscles are not involved directly in sexual activity. The purpose of this study was to evaluate the testosterone administration on trigeminal nerve motor neurons of immature castrated male rats. In this experimental study 40 one-month aged male rats were randomly divided into five groups (immature testectomy, immature testectomy + testosterone injection, immature testectomy + sesame oil injection, sham surgery, control). Testosterone (5mg/kg/day subcutaneously) was injected for one month. Then histological sections were prepared from brain stem at the level of trigeminal nerve. The length, Volume, number and density of motor nucleus neurons were calculated. The number and density of neurons in the motor nucleus of the trigeminal nerve in testectomy without testosterone injection group was significantly lower than those testectomy with testosterone injection (P<0.01). Neuronal density in the testectomy without testosterone injection showed a meaningful decrease in comparison to those of control group (P<0.05). Following injection of testosterone, neuronal density was lower in testectomy group than in the control group and this difference was not statistically significant. It seems testosterone is effective on the number of motor neurons and their density in the nucleus of the trigeminal nerve.