AXOTOMY ALTERS PUTATIVE NEUROTRANSMITTERS IN VISCERAL SENSORY NEURONS OF THE NODOSE AND PETROSAL GANGLIA

Acute peripheral axotomy of the visceral sensory neurons of the vagus and glossopharyngeal nerves removes peripheral depolarizing and trophic influences to their sensory ganglia. To study axotomy-induced changes in the putative neurotransmitters of visceral sensory neurons, rats were sacrificed 1, 3, 7 or 14 days after transection of either the cervical vagus and superior laryngeal nerves (to affect peripheral axotomy of the nodose ganglion) or the glossopharyngeal and carotid sinus nerves (to affect peripheral axotomy of the petrosal ganglion). The numbers of tyrosine hydroxylase (TH)-immunoreactive (ir), vasoactive intestinal peptide (VIP)-ir, calcitonin-gene-related peptide (CGRP)-ir, and substance P (SP)-ir neurons in the respective ganglia were analyzed in axotomized and control ganglia. In the nodose ganglion, axotomy of the cervical vagus resulted in a rapid (by 1 day) reduction in the number of TH-ir cells, whereas VIP-ir neurons were dramatically increased in number by 3 days. CGRP- and SP-ir cells in the nodose ganglion were relatively unaffected by axotomy. In the petrosal ganglion, axotomy of the glossopharyngeal and carotid sinus nerves greatly reduced the number of TH-ir cells but did not alter the number VIP-ir neurons. CGRP- and SP-ir neurons in the petrosal ganglion were reduced in number by axotomy. Thus, axotomy of visceral sensory neurons differentially changed the content and perhaps the expression of putative transmitters. Differential changes were seen among transmitters in a single ganglia and between ganglia. These data demonstrate the plasticity of putative neurotransmitter systems in visceral afferent systems of adult rats.