Effects of hypothalamic lesions on the content of dynorphin immunoreactivity in pituitary.

Radiofrequency lesion of medial basal hypothalamus (MBH) caused a approximately 50% depletion of immunoreactive dynorphin (ir-dyn) both in the anterior and neurointermediate lobe of the pituitary, whereas radiofrequency lesions of both supraoptic and paraventricular nuclei (SON, PVN) resulted in an approximately 30% reduction in neurointermediate lobe only. MBH cells and/or fibers contribute, therefore, to adenohypophysis pool of ir-dyn. Moreover, since the loss of ir-dyn in neurohypophysis ascertained after MBH lesion is significantly higher than that obtained with SON and PVN destruction, it may be assumed that MBH also participate to ir-dyn pool in neurohypophysis.