Stimulation by serotonin of vasoactive intestinal polypeptide release into rat hypophysial portal blood.
The effect of serotonin (5-HT) on plasma vasoactive intestinal polypeptide (VIP) levels in hypophysial portal blood was studied in urethane-anesthetized rats. Portal blood was collected by the parapharyngeal approach and plasma VIP was determined by radioimmunoassay. Mean (+/- SE) basal plasma VIP level was 1799 +/- 232 pg/ml, which was slightly decreased during the control experiments in which physiological saline was injected either intraventricularly or intravenously. Intraventricular injection of 5-HT (2 and 10 micrograms/rat) resulted in a significant increase in plasma VIP concentrations within 20 min. Intravenous injection of L-5-hydroxytryptophan (5-HTP, 1 mg/100 g BW), a precursor of 5-HT, also caused an increase in VIP concentrations in hypophysial portal plasma. The flow rate of hypophysial portal blood did not change throughout the experiments. These findings suggest that 5-HT stimulates VIP release from the median eminence into the hypophysial portal vessels in the rat.
D000818:Animals; D005768:Gastrointestinal Hormones / Q000097:blood*; D007276:Injections, Intraventricular; D008297:Male; D010902:Pituitary Gland / Q000098:blood supply*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000097:blood*
D005768:Gastrointestinal Hormones; D012701:Serotonin; D014660:Vasoactive Intestinal Peptide