The nitric oxide synthase inhibitor L-NAME reduces inhibitory components of somato-vesical parasympathetic reflexes in the rat

Excitatory and inhibitory A- and C-reflexes in pelvic parasympathetic efferent nerves elicited by single shock to A and C afferent fibers of perineal and limb somatic nerves in anesthetized rats

The effects of single electrical shocks to myelinated A and unmyelinated C afferent fibers of perineal and limb somatic nerves on the reflex discharges in pelvic parasympathetic (L6/S1) efferent nerves to the bladder were examined in anesthetized central nervous system (CNS)-intact and acute spinal rats. When the bladder was empty, stimulation of perineal somatic inputs to the L6 and S1 segments from the perineo-femoral branch of a pudendal nerve produced excitatory A- and C-reflex discharge components in postganglionic parasympathetic efferent nerve branches on the bladder surface. When the bladder was expanded and pelvic efferent neurons were rhythmically active, additional inhibitory A- and C-reflex components could be seen. After acute spinal transection, the same stimuli elicited excitatory A- and C-reflex discharges of similar latency as those observed before the spinal transection, but were of larger amplitude and longer duration; resting activity in the pelvic nerve was low, and no evoked inhibitory reflex components could be observed. Electrical stimulation of afferents in the tibial nerve had no effect when the bladder pressure was low, but when the bladder was distended, early and late components of reflex inhibition and excitation of parasympathetic activity were visible in CNS-intact rats; these reflex responses were abolished following spinalization.

Single electrical shock of a somatic afferent nerve elicits A- and C-reflex discharges in gastric vagal efferent nerves in anesthetized rats

The possibility that single electrical shock stimulation of somatic afferent nerves could evoke a reflex response in vagal efferent nerves innervating the stomach was examined using anesthetized, artificially-ventilated rats. A single shock to a hindlimb afferent nerve (tibial nerve) produced two distinct reflex components in gastric vagal efferent nerves; namely (1) A-reflex discharges with a latency of about 120 ms and a duration of about 200 ms elicited by stimulation of myelinated A afferent fibers, and (2) C-reflex discharges with a latency of about 360 ms and a duration of about 200 ms elicited by stimulation of unmyelinated C afferent fibers. A single shock to a first lumbar spinal afferent nerve produced only a week reflex component with a latency of about 120 ms and a duration of about 190 ms in gastric vagal efferent nerves. Limb afferents appear to have stronger central pathways functionally connecting to gastric vagal efferent preganglionic neurons in the brainstem, than do abdominal afferents.