Involvement of pedal neurons in cardio-renal regulation and their connections with identified visceral cells in Helix pomatia L.

Abstract

Involvement of the cells of pedal ganglia in the regulation of heart activity and their connections with visceral neurons was studied in the central nervous system of Helix pomatia L. It was found that (1) numerous cells of pedal ganglia receive inputs from the heart. The reaction of the pedal cells to heart afferents was characteristic: initial high frequency increase of firing followed by inhibition, then a secondary tonic increase occurred in activity. Some of the pedal cells were activated after a brief delay; (2) many of the cells of the visceral and right parietal ganglia were activated simultaneously with pedal neurons during tactile stimulation of the heart. In different ganglia the answer to heart afferents can be observed to the same or opposite directions but its duration was identical in every cell; (3) one cell of the left pedal ganglion (LP3) formed monosynaptic connections with several cells of the visceral ganglion. The axons of the visceral cells, connected monosynaptically to the neurons LP3, runs into the intestinal nerve. LP3 caused EPSPs on the visceral cells; (4) the heart excitatory motoneuron V41, simultaneously with a number of pedal cells, receives excitatory inputs from the heart. The heart excitatory motoneuron is involved in the afferent and efferent pathways of heart regulatory network; (5) a motoneuron (V43) was identified to cause relaxation of the heart, giving branches into the intestinal nerve and similarly to other motoneurons activated by heart afferents.