The electrical activity of phrenic and recurrent laryngeal motoneurons was recorded during activation of urinary bladder afferents in pentobarbital-anesthetized, paralyzed, artificially ventilated cats. Distension or spontaneous neurogenic contraction of the bladder decreased the amplitude and frequency (bursts/min) of the burst activity in these two nerves. The decrease in frequency was due mainly to a prolongation of the interburst interval (duration of expiration). Similar effects were observed during low-frequency electrical stimulation of pelvic nerve afferents with conduction velocities in the A gamma-A delta range. High-frequency stimulation of pelvic nerve afferents increased the amplitude of the burst activity in these two nerves. These results suggest an action of bladder afferents on the brain stem oscillator controlling respiratory frequency and drive. Some of the excitatory and inhibitory effects of bladder afferents on phrenic motoneurons may be mediated through spinal circuits.

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The aim of the present study was to evaluate the organization of neural circuitry responsible for the intersegmental transmission of input from urinary bladder afferents to sympathetic preganglionic neurons (SPNs). The electrical activity of SPNs was recorded from axons of the cervical sympathetic trunk in anesthetized central nervous system (CNS)-intact and in unanesthetized midcollicular-decerebrate or acute C1 spinal cats. In all three preparations, tonically active SPNs were excited or inhibited by 1) electrical stimulation of myelinated afferents of the pelvic or hypogastric nerve, both of which contain bladder afferents, and 2) spontaneous contraction or distension of the urinary bladder. The SPN responses to bladder distension were abolished by pelvic nerve section. A comparison of responses of SPNs in CNS-intact and acute spinal animals to electrical stimulation of pelvic nerve afferents suggests that both propriospinal and supraspinal circuits are involved in the intersegmental transmission of input from bladder afferents to SPNs.

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