Rat pancreatic serotonergic nerves: morphologic, pharmacologic and physiologic studies

We have previously reported the presence of a specific uptake system for serotonin in the adult rat pancreas. In this report, we extended our findings to demonstrate that this uptake is uniform throughout the pancreas, does not differ between the sexes, and does not represent uptake into platelets. Incubation of tissue fragments in vitro with [³H]serotonin (5-HT) in the presence of fluoxetine, an inhibitor of serotonin uptake, reduced the uptake to non-specific levels. Similarly, co-incubation of pancreatic fragments with parachloroamphetamine and/or 5,7-dihydroxytryptamine, both serotonergic neurotoxic drugs, completely obliterated the specific uptake of [³H]5-HT. Veratridine significantly augmented the pancreatic release of [³H]5-HT during perifusion of pancreatic fragments after uptake. It is concluded that the rat pancreas contains serotonergic nerves.