Responses of neurons in caudal solitary nucleus of female rats to stimulation of vagina, cervix, uterine horn and colon.

Neurons in the caudal part of the solitary nucleus (NTS) are known for their processing of information derived from many viscera, including cardiovascular, respiratory and alimentary tract organs. This study characterized responses of NTS neurons in female rats in estrus to mechanical stimulation of four pelvic visceral organs (i.e. the vaginal canal, cervix, uterine horn and colon) as well to gentle mechanical skin stimulation. Of the 90 neurons tested, 31% responded with excitation or inhibition to one (22%) or more (9%) visceral stimuli. Responses included 13% to vaginal distension, 12% to cervix stimulation, 10% to uterine distension and 4% to colon distension. None responded to gentle cutaneous stimuli. These results expand the domain of visceral functions of NTS neurons to include pelvic female reproductive organs. The failure of NTS neurons to respond to gentle cutaneous stimuli contrasts with convergent responses of neurons in the gracile nucleus to skin and pelvic visceral stimuli [13] indicating the two nuclei are involved in different aspects of visceral function.