title: Cardiovascular mediation of clonidine-induced ultrasound production in infant rats.
abstract: In infant rats, administration of the alpha2 adrenoceptor agonist clonidine simultaneously evokes ultrasound production and bradycardia. In this study the authors examined in 8-day-old rats whether these 2 responses to clonidine are causally related. In Experiment 1 pups were pretreated with saline or prenalterol (0.1 or 1.0 mg/kg), a beta1 adrenoceptor agonist that increases cardiac rate, followed by administration of clonidine (1.0 mg/kg). Prenalterol pretreatment suppressed clonidine-induced ultrasound production at both doses. Prenalterol also increased skin temperature, however, suggesting that suppression of ultrasound was modulated in part by increased body temperature. Consistent with this suggestion, in Experiment 2 mild hyperthermia significantly inhibited clonidine-induced ultrasound production. Finally, in Experiment 3 the authors found that the pretreatments used in Experiments 1 and 2 prevent or dampen the effects of clonidine on cardiac rate. These results suggest that clonidine's effect on ultrasound production is mediated by its effects on the cardiovascular system.
authors.affiliation: Department of Psychology, University of Iowa, Iowa City 52242-1407, USA. mark-blumberg@uiowa.edu
authors.forename: M S
authors.initials: MS
authors.lastname: Blumberg
authors.forename: L A
authors.initials: LA
authors.lastname: Kreber
authors.forename: G
authors.initials: G
authors.lastname: Sokoloff
authors.forename: K J
authors.initials: KJ
authors.lastname: Kent
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001143:Arousal / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D011292:Premedication; D011294:Prenalterol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014828:Vocalization, Animal / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011294:Prenalterol; D003000:Clonidine