Effects of clonidine on operant behavior and electric shock titration in the squirrel monkey: effects of alpha 2-adrenoreceptor antagonism.
Squirrel monkeys were studied under fixed-interval schedules in which responding was maintained either by food presentation or by termination of stimuli correlated with electric shock delivery, or under a schedule in which responses decreased the intensity of electric shock, which periodically increased in intensity (shock titration). Clonidine-HCl (0.01-1.7 mg/kg) decreased responding under the fixed-interval schedules and increased the intensity at which shock was maintained under the titration schedule. Pretreatment with the alpha 2-adrenoreceptor antagonist yohimbine-HCl (0.1-1.0 mg/kg) resulted in a 3-10-fold shift to the right in the clonidine dose-response curve. Similar antagonism was seen after pretreatment with small doses of the less selective alpha-adrenoreceptor antagonist, tolazoline-HCl (3.0, 5.6 mg/kg), but not with the alpha 1 antagonist prazosin (0.1, 0.3 mg/kg). The effects of clonidine on behavior under these conditions were apparently due to actions at alpha 2-adrenoreceptor sites.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D008297:Male; D011224:Prazosin / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012453:Saimiri; D014043:Tolazoline / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D014043:Tolazoline; D003000:Clonidine; D011224:Prazosin