RESPONSES OF NEURONS IN THALAMIC VENTROBASAL COMPLEX OF RATS TO GRADED DISTENSION OF UTERUS AND VAGINA AND TO UTERINE SUPRAFUSION WITH BRADYKININ AND PROSTAGLANDIN-F2-ALPHA

This study examined the responses of somatic-responsive neurons in and near the ventrobasal complex (VB) of halothane/nitrous oxide-anesthet ized and paralyzed estrous virgin rats to increasing levels of distens ion of the uterine horn and vaginal canal and to uterine suprafusion w ith PGF2alpha and bradykinin (BK). While individual responses of singl e neurons to uterine and vaginal distensions were idiosyncratic, as a group the neurons responded in a graded fashion to graded distensions, producing stimulus-responses functions nearly identical to those prod uced by conscious rats making escape responses to the same stimuli [Be rkley and Wood, Soc. Neurosci. Abstr., 15 (1989) 979; Berkley et al., Soc. Neurosci. Abstr., 16 (1990) 416]. In addition, most neurons respo nded vigorously to PGF2alpha and BK, with responses to BK but not PGF2 alpha, reliably preceding the 'giant' uterine contractions that were a lso produced by these algogenic agents. These results indicate that ce rtain neurons in and near VB may as a group be involved in some aspect of pain arising from female reproductive organs. The responses of the se neurons to somatic and possibly other visceral stimuli, however, po int to their potential additional involvement in other aspects of visc eral and somatic nociception.