Flexibility of the Map of Brainstem Neurons with Sympathetic Nerve-Related Activity

Abstract

Recent work from this laboratory (Barman and Gebber, 1987, 1989; Gebber and Barman, 1985) supports the view that medullary lateral tegmental field (LTF) neurons are contained in circuits responsible for basal sympathetic nerve discharge (SND). The naturally occurring activity of LTF neurons located in nucleus reticularis parvocellularis (R.pc.) and nucleus reticularis ventralis (R.v.) are correlated to the cardiac-related rhythm in postganglionic SND of baroreceptor-innervated cats anesthetized with diallylbarbiturate-urethane (DU) or its free-running 2-Hz to 6-Hz counter-part after baroreceptor denervation. These neurons fire earlier during the cardiac-related or 2-Hz to 6-Hz burst of SND than bulbospinal sympathoexcitatory neurons located in the rostral ventrolateral medulla (RVLM). Moreover, the axons of the earlier firing LTF neurons project to the region of the RVLM containing sympathoexcitatory neurons that innervate the thoracic spinal intermediolateral nucleus (IML). These observations have led us to propose that bulbospinal sympathoexcitatory neurons of the RVLM receive important driving inputs from the LTF (Barman and Gebber, 1987, 1989).