NOXIOUS DISTENSION OF VISCERA RESULTS IN DIFFERENTIAL C-FOS EXPRESSION IN 2ND-ORDER SENSORY NEURONS RECEIVING SYMPATHETIC OR PARASYMPATHETIC INPUT

Visceral organs receive dual innervation from primary afferents common ly referred to as 'sympathetic' and 'parasympathetic' afferents. We ha ve previously reported a significantly greater induction of immediate- early genes in the viscerotopically appropriate spinal cord segments r eceiving 'parasympathetic' afferent innervation (pelvic nerve) compare d with those receiving 'sympathetic' afferent innervation (hypogastric nerve) following noxious colorectal distention. In this study, the nu cleus of the solitary tract (NTS) and viscerotopically appropriate spi nal cord segments were labeled immunocytochemically for c-Fos followin g noxious gastric or esophageal distention to determine if the differe ntial labeling following 'sympathetic' (spinal) and 'parasympathetic' (vagal) visceral afferent input is a general phenomenon of the gastroi ntestinal tract. Gastric distention and esophageal distention induced considerable c-Fos in the NTS and virtually none in the thoracic spina l segments. These data suggest that 'parasympathetic' visceral afferen ts may be different than 'sympathetic' visceral afferents with respect to their ability to induce c-Fos following noxious visceral distentio n.