GABAB receptor-mediated mechanisms in human intestine in vitro.
The spontaneous motility of longitudinal muscle of human jejunum was recorded and the effect of gamma-aminobutyric acid-ergic (GABAergic) drugs was tested. GABA and (-)-baclofen (10(-6)-10(-4) M) dose dependently reduced the amplitude and frequency of the spontaneous contractions; muscimol and 3-aminopropanesulfonic acid (3 x 10(-5) M) were ineffective. The effect of 3 x 10(-5) M GABA was reduced by 3 x 10(-3) M 5-aminovaleric acid but not by 3 x 10(-5) M picrotoxin. The dose-response curve for GABA was shifted to the right by 3 x 10(-3) M 3-aminopropanesulfonic acid. Tetrodotoxin 3 x 10(-7) M prevented the GABAergic action, whereas various receptor antagonists tested did not affect it. GABAergic drugs did not influence the spontaneous motility of either circular or longitudinal muscles of human colon. It is suggested that GABAB receptor activation induces the inhibition of human jejunum longitudinal muscle motility by a neurogenic mechanism. The possible involvement of postganglionic cholinergic neurons is to be evaluated by other techniques.
Gentilini
G
G
Department of Preclinical and Clinical Pharmacology Mario Aiazzi Mancini, University of Florence, Firenze, Italy.
Franchi-Micheli
S
S
Pantalone
D
D
Cortesini
C
C
Zilletti
L
L
D003106:Colon / Q000187:drug effects / Q000502:physiology*; D005260:Female; D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D007583:Jejunum / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D011963:Receptors, GABA-A / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid