Cardiac nerve stimulation elicited more pronounced reflex renal vessel responses than muscle vessel and heart rate responses, whereas sinus pressure elevations induced equal renal and muscle responses.
The study demonstrates that ventricular receptor afferents preferentially target renal vasomotor neurons, whereas arterial baroreceptors equally affect renal and muscle vessels in cats.
The possible central integrative mechanisms, responsible for the earlier reported, differentiated reflex engagement of the renal and muscle vessels and the heart from cardiac ventricular receptors and arterial baroreceptors, respectively, were analyzed in atropinized cats. The reflux renal vessel, muscle vessel and heart rate responses, expressed as per cent of maximum, to graded activations of arterial baroreceptors (sinus pressure variations) and stimulations of ventricular receptor afferents in the cardiac nerve were systematically compared. Cardiac nerve stimulation with low frequencies was found to elicit more pronounced reflex renal vessel responses than muscle vessel and heart rate responses. In contrast, elevations of sinus pressure induced equally pronounced renal and muscle vessel responses. High frequency cardiac nerve stimulation elicited maximal reflex renal vessel responses, but only submaximal effects on muscle vessels and heart rate, while intense baroreceptor stimulation induced maximal reflex effector responses throughout. The submaximal heart rate response to cardiac nerve stimulation is probably due to a simultaneous activation of excitatory afferents. On the other hand, the less pronounced muscle than renal vessel responses when the cardiac nerve was stimulated probably reflect a relatively sparse innervation of muscle vasomotor neurons by ventricular receptor afferents, which seem instead to be preferentially oriented towards renal vasomotor and, possibly, cardiac motor neurons.
Little et al. (1975) studied this question. Activation of arterial baroreceptors and stimulation of ventricular receptor afferents was evaluated on Reflex renal vessel, muscle vessel and heart rate responses. Cardiac nerve stimulation elicited more pronounced reflex renal vessel responses than muscle vessel and heart rate responses, whereas sinus pressure elevations induced equal renal and muscle responses.