Androgen receptors in cranial nerve motor nuclei of male and female rats

This study compared AR proteins in four cranial nerve motor nuclei among ma le and female rats that were intact, gonadectomized, or gonadectomized and given TP by immunohistochemistry. AR-immunoreactive (ir) neurons were found , in descending order of abundance, in the nucleus ambiguus, hypoglossal nu cleus, and the facial and trigeminal motor nuclei of both males and females of intact and gonadectomized plus TP rats. Virtually every neuron of the n ucleus ambiguus was AR-ir. In contrast, AR-ir neurons were either restricte d to a specific area of the hypoglossal nucleus, or randomly distributed in the facial and trigeminal motor nuclei. The predominant AR-ir site shifted front cell nuclei to the cytoplasm, depending upon the presence or absence of ligand. Sex differences in the amount and staining intensity of AR-ir n eurons were discernable in all four motor nuclei of intact rats, and these differences were maintained in gonadectomized plus TP rats, with the except ion of the nucleus ambiguus. The immunostaining results were complemented b y results from AR binding studies. Cytosolic AR binding values for the hypo glossal and facial motor nuclei of females were only similar to 50% of thos e of males despite the absence of a sex difference in neuron number. These results indicate that intrinsic sex differences in AR levels and androgenic regulation of AR exist in cranial nerve motor nuclei, and that there are d ifferences in the abundance and distribution pattern of AR responsive neuro ns in cranial nerve motor nuclei. These results are consistent with the ide a that sex differences in AR could account for sex differences observed in nerve regeneration and neuron loss following cranial nerve injury. (C) 2000 John Wiley & Sons, Inc.