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THE EFFECT OF SOME α 2 ‐ADRENOCEPTOR AGONISTS AND ANTAGONISTS ON GASTROINTESTINAL TRANSIT IN MICE: INFLUENCE OF MORPHINE, CASTOR OIL AND GLUCOSE
Author(s) -
Ali B. H.,
Bashir A. A.
Publication year - 1993
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1993.tb01495.x
Subject(s) - yohimbine , idazoxan , clonidine , gastrointestinal transit , chemistry , tizanidine , endocrinology , pharmacology , medicine , morphine , antagonist , prazosin , anesthesia , receptor , spasticity
SUMMARY 1. The effects of graded doses of the α 2 ‐adrenoceptor agonists clonidine, tizanidine and BHT‐920, and the α 2 ‐adrenoceptor antagonists yohimbine and idazoxan, on gastrointestinal transit were investigated in mice using the charcoal meal test. 2. The agonists produced significant and dose‐dependent decreases in gastrointestinal transit, and the antagonists produced the opposite effect. In affecting the gastrointestinal transit, clonidine (1 mg/kg) was as effective as tizanidine (12 mg/kg) and BHT‐920 (40 mg/kg), while yohimbine (2 mg/kg) was as effective as idazoxan (1 mg/kg). 3. Morphine (2, 4 and 8 mg/kg) significantly inhibited gastrointestinal transit. This effect was significantly reversed by the co‐administration of yohimbine (2 mg/kg) and idazoxan (1 mg/kg). 4. The acute administration of glucose (5.04 g/kg, i.p.) potentiated the inhibition of gastrointestinal transit produced by clonidine (1 mg/kg) and BHT‐920 (40 mg/kg). Glucose treatment, however, had no significant effect on the increase in gastrointestinal transit induced by yohimbine (2 mg/kg) or idazoxan (1 mg/kg). 5. Castor oil (0.25 mL/mouse, orally) induced diarrhoea in saline‐treated animals within about 45 min. Clonidine (1 mg/kg), tizanidine (12 mg/kg) and BHT‐920 (40 mg/kg) delayed the occurrence of diarrhoea to 2.1, 1.2 and 1.4 h, respectively.