Effects of gonadectomy and testosterone replacement on growth hormone response to alpha 2 adrenergic stimulation in the male rat.

The growth hormone (GH) response to clonidine in reserpine-pretreated rats is a putative in vivo model to reflect activation of central postsynaptic alpha 2 receptors. In the present study the influence of testosterone on the responsiveness of central alpha 2 receptors was investigated using this method. One week after operation the GH response to clonidine was drastically reduced in gonadectomized adult male rats compared to sham-operated controls. Testosterone replacement completely antagonized the effect. The results suggest an influence of testosterone on central postsynaptic alpha 2 receptors or on structures connected to these receptors.