5-Carboxamidotryptamine is a selective agonist at 5-hydroxytryptamine receptors mediating vasodilatation and tachycardia in anaesthetized cats.

Abstract

We have attempted to characterize the 5-hydroxytryptamine (5-HT) receptors mediating bronchoconstriction, vasodilatation, vasodepression and tachycardia in anaesthetized cats following bilateral vagosympathectomy and beta-adrenoceptor blockade with propranolol. 5-HT (1-100 micrograms/kg-1 i.v.) caused dose-related bronchoconstriction and tachycardia but variable and complex effects on diastolic blood pressure and carotid arterial vascular resistance. In contrast, 5-carboxamidotryptamine (5-CT; 0.01-1 micrograms kg-1 i.v.) caused consistent, dose-related decreases in diastolic blood pressure and carotid arterial vascular resistance and increases in heart rate. 5-CT did not cause bronchoconstriction. The 5-HT-induced bronchoconstriction was dose-dependently antagonized by methiothepin, methysergide and ketanserin (10-100 micrograms kg-1 i.v.). The highest doses used of these antagonists did not antagonize bronchoconstriction induced by prostaglandin F2 alpha. The high potency of all three antagonists indicate a 5-HT2-receptor mediated effect. The 5-HT- and 5-CT-induced tachycardia as well as the 5-CT-induced vasodepressor and carotid arterial vasodilator responses were dose-dependently antagonized by low doses of methiothepin (10-100 micrograms kg-1 i.v.) and by high doses of methysergide (100-1000 micrograms kg-1 i.v.) but were little affected by ketanserin in doses up to 1000 micrograms kg-1 i.v. These selective effects of 5-CT appear to be mediated by '5-HT1-like' receptors.

• Authors: H E Connor, W Feniuk, P P Humphrey, M J Perren
• Journal: British journal of pharmacology (Br J Pharmacol) Vol. 87 Issue 2 Pg. 417-26 (Feb 1986) ISSN: 0007-1188 [Print] England
• PMID: 2937503 (Publication Type: Journal Article)

Chemical References

• Piperidines
• Receptors, Serotonin
• Serotonin Antagonists
• Serotonin
• Methiothepin
• 5-carboxamidotryptamine
• Ketanserin
• Methysergide

Topics

• Animals
• Blood Pressure (drug effects)
• Cats
• Female
• Heart Rate (drug effects)
• Ketanserin
• Male
• Methiothepin (pharmacology)
• Methysergide (pharmacology)
• Piperidines (pharmacology)
• Receptors, Serotonin (drug effects, physiology)
• Serotonin (analogs & derivatives, pharmacology)
• Serotonin Antagonists (pharmacology)
• Vascular Resistance (drug effects)
• Vasodilation (drug effects)