Modulatory effect of serotonin on the acetylcholine sensitivity of identified neurons in the brain of Helix pomatia L.

Excitatory effect of acetylcholine (ACh) was modified by serotonin (5-HT) on identified neurons of intact brain with partially preserved functional connections at Helix pomatia L. Depolarization caused by ACh on neuron LPa3 and on several spontaneously active cells of the visceral ganglion was enhanced by brief application of 5-HT to the soma of these neurons. Guanosine triphosphate (GTP) and theophylline caused similar effects to the serotonin changes in ACh sensitivity of these cells. ACh sensitivity of neurons RPa3 and RPa2 was reduced following application of 5-HT, GTP and theophylline. Similarly, the effect of 5-HT tactile stimulation of the heart caused decrease in ACh sensitivity of neuron RPa2.