Abstract
The role of β-adrenergic receptors in regulating cutaneous water evaporation (CWE) in the rock pigeon (Columba livia) is well documented. Here, we studied the involvement of the α2-adrenergic receptors in this cooling mechanism of the heat-acclimated (HAc) pigeon. Systemic α2-adrenergic activation [clonidine, 50 μg kg-1, intramuscular (i.m.)] was found to increase CWE in heat-acclimated pigeons at an ambient temperature (Ta) of 25°C. Subcutaneous administration of the drug had no significant effect. Preinjection of an α2- adrenergic antagonist (yohimbine, 10 mg kg-1, i.m.) completely prevented clonidine-induced CWE and attenuated propranolol-induced CWE by 53%. Pretreatment with a β-adrenergic agonist (isoproterenol, 4 mg kg -1, i.m.) abolished the effect of clonidine. None of the above treatments was found to elicit significant CWE in nonacclimated (NAc) pigeons. These findings, in addition to previously reported data, indicate a complex regulatory pathway of CWE in the heat-acclimated pigeon consisting of α2- and β2-adrenergic receptors. The possible hierarchical pattern of these receptors is discussed.
Original language | English |
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Pages (from-to) | 411-415 |
Number of pages | 5 |
Journal | Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology |
Volume | 139 |
Issue number | 4 |
DOIs | |
State | Published - Dec 2004 |
Externally published | Yes |
Keywords
- Birds
- Clonidine
- Cutaneous water evaporation
- Heat-acclimation
- Pigeon
- Skin
- Thermoregulation
- α-Adrenergic receptors
ASJC Scopus subject areas
- Biochemistry
- Physiology
- Molecular Biology