Effects of alpha-adrenoceptor agonists and antagonists in a maze-exploration model of 'fear'-motivated behaviour.
An elevated X-maze with alternating open and enclosed arms was investigated as a model for the study of fear-induced behaviour. As predicted, the anxiolytics diazepam and amylobarbitone increased, and the putative anxiogenics ACTH and picrotoxin decreased the proportion of open arm entries. The alpha 1-adrenoceptor agonists phenylephrine and ST587, and the alpha 2-adrenoceptor antagonists idazoxan, piperoxane, RS-21361 and yohimbine decreased relative open-arm entries, thus resembling the putative anxiogenics. On the other hand, azepexole, clonidine and guanabenz, agonists at alpha 2-adrenoceptors, and the alpha 1-adrenoceptor antagonists prazosin and thymoxamine, enhanced the proportion of open arm entries at low doses, suggesting anxiolytic-like properties. A paradoxical fall in open arm entries occurred with these agents at higher doses. These results provide further evidence for the involvement of noradrenergic systems in 'fear'-motivated behaviour.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000654:Amobarbital / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology; D005106:Exploratory Behavior / Q000187:drug effects*; D005239:Fear; D008297:Male; D008960:Models, Psychological; D010852:Picrotoxin / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000324:Adrenocorticotropic Hormone; D000654:Amobarbital; D003000:Clonidine; D003975:Diazepam; D010852:Picrotoxin; D011224:Prazosin