Inhibition of tetrahydroisoxazolo-pyridin-3-ol and muscimol and its mechanism on gastrointestinal transit in mice.
The effect of tetrahydroisoxazolo-pyridin-3-ol (THIP) and muscimol on gastrointestinal transit and a possible mechanism for this effect were studied using the charcoal meal test in mice. These agents inhibited transit dose relatedly. The inhibitory effect was completely reversed by yohimbine and phentolamine. A minor degree of antagonism by bicuculline was observed. There were an additive response in morphine-pretreated animals and partial antagonism in naloxone-pretreated animals. Propranolol failed to modify the inhibitory effect. The findings suggest a predominantly alpha 2-receptor-mediated inhibitory effect on gastrointestinal transit for THIP and muscimol which possibly also utilizes opioid pathways. However, it appears that beta-adrenergic and GABAergic systems might not contribute to this effect.
Ramaswamy
S
S
Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India.
Srinivasan
D
D
Bapna
J S
JS
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005772:Gastrointestinal Transit / Q000187:drug effects*; D007555:Isoxazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009118:Muscimol / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D007555:Isoxazoles; D009118:Muscimol; D015016:Yohimbine; D011433:Propranolol; C015542:gaboxadol; D001640:Bicuculline; D010646:Phentolamine