A study of peripheral input to and its control by post‐ganglionic neurones of the inferior mesenteric ganglion.

Abstract

SUMMARY1. Intracellular recordings were made, in vitro, from neurones of guinea-pig inferior mesenteric ganglia (IMG) attached, via the lumbar colonic nerves, to segments of distal colon.2. 'Spontaneous' synaptic input from colonic afferent fibres was observed in 79% of the neurones tested. In any given preparation, the level and pattern of this synaptic input to different neurones varied considerably. 3. Superfusion of colonic segments with drugs (papaverine, isoprenaline, and adenosine triphosphate) which reduce colonic motility decreased colonic afferent input to IMG neurones. 4. Superfusion of colonic segments with acetylcholine or stimulation of pelvic nerves, both of which increase colonic motility, increased colonic afferent input to 1MG neurones.5. Superfusion of colonic segments with either atropine or tubocurarine reduced the level of 'spontaneous', colonic afferent input. However, distension of these relaxed segments increased the colonic afferent input.6. Repetitive stimulation of preganglionic inputs to the IMG inhibited afferent input from drug relaxed segments of colon that were moderately distended by the injection of air into the lumen. Superfusion of the colon with phentolamine blocked this inhibition.7. The results of this study suggest that IMG neurones receive afferent input from mechanoreceptors located in the distal colon and that the mechanosensitivity of this afferent pathway is in part controlled by efferent noradrenergic neurones of the IMG. The IMG-colon neural circuitry can therefore be considered to form a feed-back control system which participates in the regulation of colonic motility.

A study of renal‐efferent neurones and their neural connexions within cat renal ganglia using intracellular electrodes.

“…The concept that neurones within prevertebral ganglia receive direct sensory input from visceral organs is not new (Kuntz, 1938(Kuntz, , 1940Szurszewski & Weems, 1976b). Neurones within the inferior mesenteric, superior mesenteric and coeliac ganglia directly receive afferent input from mechanoreceptors located in the colon (Szurszewski & Weems, 1976a;Kreulen & Szurszewski, 1979a, b). Direct, renal-afferent input to renal ganglia neurones may be another example of a prevertebral ganglion receiving sensory input from an organ that is innervated by axons originating in that ganglion.…”

Neuronal regulation of cochlear blood flow in the guinea‐pig.

“…Several studies have shown that, in certain organs, stimulation of either preganglionic efferent fibres or the afferent limb of an autonomic nervous system reflex loop results in an inhibitory effect in the target organ (Porszasz, Such & Porszasz-Gibiszer, 1972;Such, Porszasz & Gibiszer, 1972;Flock & Russell, 1976;Szurszewski & Weems, 1976).…”

Fast and slow synaptic potentials produced in a mammalian sympathetic ganglion by colon distension.

“…The fibers activated by stimulation of the latter could be of two kinds: (i) branches of primary sensory neurons that traverse the ganglia (8,9) and (ii) afferent neurons located in the gastrointestinal tract that project to the ganglia (8,(10)(11)(12). A cholinergic mechanosensory pathway to the prevertebral ganglia from the colon of the guinea pig has been described (13)(14)(15)(16)(17). Activation ofthis pathway by distension of the colon results in an increase in the frequency and amplitude of cholinergic EPSPs in ganglionic neurons.…”