The effect of callosotomy on testicular steroidogenesis in hemiorchidectomized rats: a pituitary-independent regulatory mechanism

In recent years, increasing number of data indicate that cerebral structures exert a direct, pituitary-independent, neural regulatory action on the endocrine glands. In addition, both experimental and clinical observations indicate functional asymmetry of the control system. Therefore, the objective of the present study was to study the effect of callosotomy on testicular steroidogenesis and serum gonadotrop concentrations in rats subjected to left- or right-sided orchidectomy. In animals underwent callosotomy plus left-sided orchidectomy the basal testosterone secretion in vitro of the remaining (right) testis was significantly higher than that of intact controls, and of rats subjected to sham surgery plus left orchidectomy. In contrast, either sham operation or callosotomy plus right-sided orchidectomy did not interfere with testicular steroidogenesis. Sham surgery or callosotomy plus left orchidectomy induced a significant rise in serum follicle-stimulating hormone concentration while right orchidectomy combined either with sham surgery or callosotomy did not alter this parameter. There was no statistically significant difference between experimental groups in serum testosterone and luteinizing hormone concentrations. The results indicate the involvement of the corpus callosum in a pituitary-independent neural control of testicular steroidogenesis. The data further suggest a different response in steroidogenesis of the left and the right testis following hemicastration and callosotomy.