Mr. Zarrindast et al., Influence of different adrenoceptor agonists and antagonists on physostigmine-induced yawning in rats, PHARM BIO B, 62(1), 1999, pp. 1-5
In the present study, effects of adrenoceptor agonists and antagonists on p
hysostigmine-induced yawning was investigated. Intraperitoneal (IP) injecti
on of different doses of physostigmine (0.03, 0.05, 0.1, and 0.2 mg/kg) ind
uced yawning in rats. The maximum response was obtained by 0.2 mg/kg of the
drug. The alpha(1)-adrenoceptor agonist, phenylephrine, and the alpha(2)-a
drenoceptor agonist, clonidine, decreased yawning induced by physostigmine.
Prazosin and higher doses of phenoxybenzamine reduced the inhibitory effec
t of phenylephrine. Higher doses of yohimbine also reduced the clonidine re
sponse. The adrenoceptor antagonists, prazosin, phenoxybenzamine, and propr
anolol, did not significantly alter the physostigmine response. However, yo
himbine, or lower doses of prazosin, decreased the physostigmine response.
It may be concluded that alpha(1)- and alpha(2)-adrenoceptor stimulation de
creases the physostigmine-induced yawning behavior in rats. (C) 1998 Elsevi
er Science Inc.