Unilateral paramedian-sagittal brain cut extending from the level of the anterior commissure to the midlevel of the third ventricle above the amygdala affects gonadal function in male rat: a lateralized effect.

The aim of the present investigations was to study involvement of fiber systems to and from the insular cortex above the amygdala in the neural control of the hypophysio-testicular axis in male rats. Animals were subjected to a unilateral paramedian-sagittal brain cut above the amygdala, extending from the level of the anterior commissure to the midlevel of the third ventricle and causing among others partial deafferentation of the insular cortex. Right-sided cut induced a significant rise in basal testosterone secretion in vitro of both testes as compared to intact or sham-operated controls without affecting serum testosterone level. By contrast, left-sided cut slightly suppressed testicular steroidogenesis and significantly decreased serum testosterone concentration. In animals underwent sham or actual cut on either side, serum luteinizing hormone levels were similar, but significantly lower than those in intact controls. No change was observed in serum FSH concentration of any experimental group. The results indicate that afferent and efferent connections of the partially deafferented cortical regions including among others the insular cortex are involved in the control of testosterone secretion. The data further suggest functional laterality of the interrupted structures.