Serotonin receptors for chloride secretion in hen colon

1. The effect of serotonin on chloride secretion in hen colon was studied under short circuit conditions. 2. Serotonin added to the serosal side induced a short-lived peak increase in Cl(-)-secretion (6.2 +/- 1.0 mumole.cm-2.h-1), in short circuit current (5.4 +/- 0.7 mumole.cm-2.h-1) and in cord conductance (8.1 +/- 0.7 mS.cm-2) with an apparent EC50 around 8 microM, and a more prolonged rise in chloride secretion of around 3.0 mumole.cm-2.h-1. 3. The short circuit current is a reasonable measure of net chloride secretion at the peak. 4. Several specific and non-specific serotonin receptor antagonists were studied for their influence on the serotonin induced peak response in short circuit current and cord conductance. 5. These antagonists covered the whole range of currently defined serotonin receptor types and subtypes: 5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D, 5-HT2, and 5-HT3. 6. Adrenergic, cholinergic and histaminergic receptor antagonists were also tested for an interaction at the serotonin receptor involved in Ca(-)-secretion. 7. None of the antagonists had any influence on the serotonin response in short circuit current or cord conductance.