RESPONSES OF LUMBAR VASOCONSTRICTOR NEURONS SUPPLYING DIFFERENT VASCULAR BEDS TO GRADED BARORECEPTOR STIMULI IN THE CAT

Lumbar sympathetic vasoconstrictor neurons supplying skeletal muscle, hairy skin and pelvic organs were tested for their responses to carotid baroreceptor stimulation in chloralose-anaesthetized cats. Using single- and few-fibre recordings, the responses of the different types of vasoconstrictor neuron to graded steps of non-pulsatile pressure ranging from 110 to 260 mmHg in a vascularly isolated carotid sinus were analyzed quantitatively during the first 10 s of stimulation. The activity in all postganglionic muscle vasoconstrictor (MVC) neurons, preganglionic visceral vasoconstrictor (VVC) neurons and one third of the postganglionic cutaneous vasoconstrictor (CVC1) neurons was strongly depressed by maximal baroreceptor stimulation. Moreover, quantitative analysis revealed no significant differences of the baroreceptor sensitivity of MVC and CVC1 neurons as compared with VVC neurons at all levels of carotid sinus pressure. In contrast, two-thirds of the postganglionic cutaneous vasoconstrictor (CVC2) neurons exhibited a significantly weaker barosensitivity. The functional implications are discussed.