Abstract
Clonidine (150 Μg/kg s. c.) depressed avoidance conditioned reflexes in Long-Evans rats. Some α-adrenoceptor blocking agents piperoxan, tolazoline, phentolamine, dibenamine and phenoxybenzamine also depressed these reflexes. Yohimbine (1–2 mg/kg) was found to have no significant effect. Atropine (10 to 15 mg/kg i. p.) antagonized the depression of conditioned avoidance reflexes induced by α-adrenoceptor blocking agents as well as the depression produced by clonidine.
Yohimbine (1–2 mg/kg) reduced the depressing effects of clonidine on avoidance conditioned reflexes. In rats treated with piperoxan (10 mg/kg) the effects of clonidine were reduced. In these rats the depression of conditioned reflexes was less than in rats treated with clonidine or piperoxan alone.
These experiments suggest that clonidine depressed avoidance conditioned reflexes in rats by activating central α-adrenoceptors. It is proposed that α-adrenoceptor blocking agents might act as partial agonists.
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Delbarre, B., Schmitt, H. Effects of clonidine and some α-adrenoreceptor blocking agents on avoidance conditioned reflexes in rats: Their interactions and antagonism by atropine. Psychopharmacologia 35, 195–202 (1974). https://doi.org/10.1007/BF00437748
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DOI: https://doi.org/10.1007/BF00437748