Effect of substance P on venous tone in conscious rats.
Substance P is an undecapeptide that belongs to the mammalian tachykinin family. We investigated the effects of substance P on venous tone in conscious rats through measurement of mean circulatory filling pressure. The effects of substance P (10 and 30 nmol/kg, IV) and the vehicle (0.9% NaCl) on mean arterial pressure, heart rate, and mean circulatory filling pressure were examined in 2 groups each of conscious rats: rats without or with ganglionic blockade through pretreatment with mecamylamine (10 mg/kg, IV) and norepinephrine (4 microg/kg/min, IV). In the unblocked rats, both doses of substance P reduced mean arterial pressure (-19 +/- 1 and -35 +/- 2 mm Hg) and increased heart rate (+113 +/- 14 and +115 +/- 23 beats/min). The high dose of substance P also decreased mean circulatory filling pressure (-1.7 +/- 0.3 mm Hg). In the ganglionic-blocked rats, both doses of substance P decreased mean arterial pressure (-48 +/- 6 and -73 +/- 6 mm Hg) and mean circulatory filling pressure (-2.9 +/- 0.4 and -4.2 +/- 0.8 mm Hg) but did not affect HR. In conclusion, substance P is a vasodilator peptide that has a prominent venodilator action.
Abdelrahman
Aly Mohamed
AM
Department of Pharmacology, College of Medicine and Health Sciences, Sultan Qaboos University, Sultanate of Oman.
Pang
Catherine Cheuk Ying
CC
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D003243:Consciousness; D004305:Dose-Response Relationship, Drug; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000494:pharmacology / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014680:Veins / Q000187:drug effects / Q000502:physiology*
D005730:Ganglionic Blockers; D014662:Vasoconstrictor Agents; D013373:Substance P; D008464:Mecamylamine; D009638:Norepinephrine