Motilin effects on the heart and blood vessels of the pithed rat.
Motilin, a 22 amino acid polypeptide was shown to affect smooth muscle tone in the gastrointestinal tract. However, its widespread distribution in peripheral and central components of the autonomic nervous system suggest a role in other functions such as regulation of vascular tone and hemodynamic variables. Therefore, the effect of motilin on vascular tone, cardiac rhythm and blood vessel response to pressor stimuli was studied in the pithed rat. It is shown that motilin produces a prolonged depressor effect. The depressor responses were dose dependent at the range of 30 - 300 nmol/kg (max. decrease: -22 +/- 4 mmHg). In addition, motilin attenuated pressor responses to vasopressin, leukotriene D4, and the pressor effect evoked by complete spinal cord stimulation. Motilin did not affect the basal heart rate nor did it alter sympathetically induced heart rate acceleration. Motilin did not affect the circulatory level of norepinephrine or epinephrine at resting state or of norepinephrine released by spinal cord stimulation; motilin significantly suppressed epinephrine released by spinal cord stimulation. These data suggest a role for motilin in regulation of blood vessel tone by direct action on the vascular smooth muscle. In addition, motilin might play a role in regulation of epinephrine release from the adrenal medulla.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood; D005768:Gastrointestinal Hormones / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009037:Motilin / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000187:drug effects*
D002395:Catecholamines; D005768:Gastrointestinal Hormones; D009037:Motilin