Evidence that neurotensin mediates postprandial intestinal hyperemia in the python, Python regius.
Digestion of large meals in pythons produces substantial increases in heart rate and cardiac output, as well as a dilation of the mesenteric vascular bed leading to intestinal hyperemia, but the mediators of these effects are unknown. Bolus intra-arterial injections of python neurotensin ([His(3), Val(4), Ala(7)]NT) (1 - 1,000 pmol/kg) into the anesthetized ball python Python regius (n = 7) produced a dose-dependent vasodilation that was associated with a decrease in systemic pressure (P(sys)) and increase in systemic blood flow (Q(sys)). There was no effect on pulmonary pressure and conductance. A significant (P < 0.05) increase in heart rate (f(H)) and total cardiac output (Q(tot)) was seen only at high doses (>30 pmol/kg). The systemic vasodilation and increase in Q(tot) persisted after beta-adrenergic blockade with propranolol, but the rise in f(H) was abolished. Also, the systemic vasodilation persisted after histamine H(2)-receptor blockade. In unanesthetized pythons (n = 4), bolus injection of python NT in a dose as low as 1 pmol/kg produced a significant increase in blood flow to the mesenteric artery (177% +/- 54%; mean +/- SE) and mesenteric conductance (219% +/- 74%) without any increase in Q(sys), systemic conductance, P(sys), and f(H). The data provide evidence that NT is an important hormonal mediator of postprandial intestinal hyperemia in the python, but its involvement in mediating the cardiac responses to digestion may be relatively minor.
Skovgaard
Nini
N
Zoophysiology, Department of Biological Sciences, Aarhus University, 8000 Aarhus C, Denmark. nini.jensen@biology.au.dk
Conlon
J Michael
JM
Wang
Tobias
T
D000758:Anesthesia; D000818:Animals; D005075:Biological Evolution; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects; D006940:Hyperemia / Q000503:physiopathology*; D007422:Intestines / Q000098:blood supply* / Q000187:drug effects / Q000502:physiology*; D009496:Neurotensin / Q000494:pharmacology / Q000502:physiology*; D019518:Postprandial Period / Q000187:drug effects / Q000502:physiology*; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology; D012911:Snakes / Q000502:physiology*; D013152:Splanchnic Circulation / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects
D009496:Neurotensin