Effect of 5-HT Receptor Agonists or Antagonists on Hypothalamic 5-HT Release or Colonic Temperature in Rats

Intraperitoneal administration of either l-(3-chlorophenyl)-piperazine (5-HT1 receptor agonist), 8-hydroxy-DPAT (5-HT1A receptor agonist), CGS-12066B (5-HT1B receptor agonist), DOI (5-HT2 receptor agonist) or 2-methyl-serotonin (5-HT3 receptor agonist) produced dose-dependent decrease in both the colonic temperature and the hypothalamic 5-HT release measured by in vivo voltammetry in unanaesthetized rats. On the other hand, intraperitoneal administration of propranolol, S(-) (5-HT1 receptor antagonist)or ketanserine (5-HT2 receptor antagonist) caused dose-dependent increase in both the colonic temperature and the hypothalamic 5-HT release in rats.