Mode of action of neurotensin on the spontaneous and electrically-induced contractions of gastric smooth muscle.
Mechanical activity was recorded from muscle preparations isolated from the guinea-pig stomach. Neurotensin (10(-11) M to 10(-7) M) produced dose-dependent tonic contractions and showed a higher affinity but lower efficiency compared to acetylcholine (ACH). Atropine and tetrodotoxin had no effect on the neurotensin responses. Blockade of prostaglandin (PG) synthesis by indomethacin or cortisone (5 X 10(-6) M) shifted to the right the dose-response curve for neurotensin (NT) and significantly reduced the NT maximum responses. The data suggest the involvement of PG-mechanisms in the myogenic effect of neurotensin. The electrically-induced, atropine-sensitive contractions (5 to 10 Hz, 0.3 to 0.5 ms) of the muscle strips were inhibited by NT (10(-11) M to 10(-9) M). This inhibition was overcome by yohimbine (10(-6) M) or prostaglandin F2a. It is concluded that NT modulates cholinergic neurotransmission in gastric smooth muscle probably via presynaptically located adrenoceptors.
Institute of Physiology, Bulgarian Academy of Sciences.
K
K
Milenov
A
A
Rakovska
A
A
Bocheva
M
M
Vassileva
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009496:Neurotensin / Q000494:pharmacology*; D011453:Prostaglandins / Q000502:physiology; D013270:Stomach / Q000187:drug effects
D011453:Prostaglandins; D009496:Neurotensin; D000109:Acetylcholine