Susceptibility to Adenosine Agonists of Giant Migrating Contractions Induced by Glycerol Enema in Anesthetized Rats

Abstract

The present study examined whether adenosine agonists influence the occurrence of giant migrating contractions (GMCs) induced by glycerol enema (65%, 2 ml/kg) in rats. Catheter pressure transducers were used to measure the colonic luminal manometric alterations. The adenosine A₁ agonists (2S)-N⁶-(2-endo-norbornyl)adenosine ((S)-ENBA) (10 μg/kg, i.v.) and N⁶-cyclohexyladenosine (30 μg/kg, i.v.) abolished the GMCs, whereas the adenosine A₂ agonist 2-[p-(2-carboxyethyl)phenethylamino]-5''-N-ethylcarboxamidoadenosine (CGS 21680) (30-300 pg/kg, i.v.) failed to influence the GMCs. The suppressive action of (S)-ENBA on the GMCs was entirely counteracted by the peripheral adenosine antagonist 8-(p-sulfophenyl)theophylline (10 mg/kg, i.v.). The present observations suggest that the adenosine A₁ agonist suppresses the GMCs via peripheral adenosine receptors.