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Cardiovascular mediation of clonidine-induced ultrasound production in infant rats
M S Blumberg1, L A Kreber, G Sokoloff
1Department of Psychology, University of Iowa, Iowa City 52242-1407, USA. mark-blumberg@uiowa.edu
Insights
Clonidine, an alpha2 adrenoceptor agonist, triggers ultrasound production and bradycardia in infant rats. This study suggests clonidine
Area of Science:
- Neuropharmacology
- Developmental Neuroscience
- Cardiovascular Physiology
Background:
- Alpha2 adrenoceptor agonist clonidine induces both ultrasound vocalizations and bradycardia in infant rats.
- The causal relationship between these two clonidine-induced responses in early development remains unclear.
Purpose of the Study:
- To investigate the causal link between clonidine-induced ultrasound production and bradycardia in 8-day-old rat pups.
Main Methods:
- Experiment 1: Prenalterol (beta1 adrenoceptor agonist) pretreatment to alter cardiac rate, followed by clonidine administration.
- Experiment 2: Induction of mild hyperthermia to assess its effect on clonidine-induced ultrasound.
- Experiment 3: Evaluation of clonidine's cardiovascular effects after pretreatments from Experiments 1 and 2.
Main Results:
- Prenalterol pretreatment significantly suppressed clonidine-induced ultrasound production, an effect potentially modulated by increased body temperature.
- Mild hyperthermia also inhibited clonidine-induced ultrasound production.
- The applied pretreatments attenuated clonidine's effects on cardiac rate.
Conclusions:
- Clonidine's impact on ultrasound production in infant rats appears to be mediated through its effects on the cardiovascular system.
- This suggests a potential link between cardiovascular regulation and vocalization behavior during early development.
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.