Cat pancreatic neurons: morphology, electrophysiological properties, and responses to 5-HT.

Light and confocal microscopy was used to study the anatomy and morphology of cat pancreatic ganglia. Intracellular microelectrodes were used to examine the electrophysiological properties of neurons in the head, body, and tail regions of the pancreas and to compare their responses to 5-hydroxytryptamine (5-HT). Pancreatic ganglia were oval shaped, joined by interconnecting nerves. Several head to tail gradients were found: (1) ganglion cell numbers decreased from head to tail; (2) the incidence of ongoing synaptic activity was higher for neurons located in the head region; (3) ganglion neurons in the head region received a greater number of converging synaptic inputs; (4) a greater percentage of neurons in the head region responded to 5-HT; (5) a greater percentage of neurons in the head region exhibited depolarizing responses mediated by 5-HT3 receptors; and (6) late slow-excitatory postsynaptic potentials recorded from neurons in the head region were more often antagonized by 5-HT1P receptor antagonists. It was concluded that cat pancreatic ganglia are sites of convergence and integration of synaptic inputs arriving from multiple sources. Serotonergic inputs from enteropancreatic nerves, if they exist in the cat pancreas, would be expected to have a significant influence on the excitability of neurons located in the head region compared to neurons located in the tail region of the pancreas.