Activation of peripheral cardiovascular receptors altered the firing frequency of 49 of 81 single units in the ventrolateral medulla, suggesting they are components of bulbospinal pathways.
Does selective activation of peripheral chemoreceptors and baroreceptors alter the firing frequency of ventrolateral medullary neurons in cats?
Neurons in the ventrolateral medulla are components of bulbospinal pathways that receive cardiovascular afferent information and influence autonomic outflow.
Recording experiments were done in chloralose-anesthetized, paralyzed, and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) projecting directly to the region of the intermediolateral nucleus of the spinal cord (T2) and responding to selective activation of peripheral chemoreceptors (sodium cyanide, 20-60 micrograms in 0.1-0.3 ml saline into medial thyroid artery) and baroreceptors (phenylephrine, 2 micrograms/kg iv). The firing frequency of 49 of the 81 antidromically identified single units was altered by activation of the peripheral cardiovascular receptors. Of these responsive units, 25 responded only to activation of chemoreceptors (17 excited and 8 inhibited), 20 responded in various combinations to activation of both chemo- and baroreceptors, and 4 responded only to activation of baroreceptors. In addition, units that altered their firing frequency during baroreceptor activation (n = 24) responded in the opposite direction to baroreceptor unloading (carotid arterial occlusion). These results suggest that neurons in the VLM are components of bulbospinal sympathoexcitatory and -inhibitory pathways that receive cardiovascular afferent information and in turn influence vasoconstrictor and cardioacceleratory neurons in the intermediolateral nucleus of the upper thoracic cord.
Caverson et al. (Thu,) reported a other. Selective activation of peripheral chemoreceptors and baroreceptors was evaluated on Firing frequency alteration of antidromically identified single units. Activation of peripheral cardiovascular receptors altered the firing frequency of 49 of 81 single units in the ventrolateral medulla, suggesting they are components of bulbospinal pathways.