Thermally induced peripheral blood flow changes in chickens.

Area of Science:

• Physiology
• Thermoregulation
• Vascular Biology

Background:

• The wattle's role in avian thermoregulation is crucial.
• Understanding wattle vascular responses to thermal stress is important.

Purpose of the Study:

• To investigate changes in wattle blood flow and vascular resistance during local and general heating.
• To identify the specific receptor pathways involved in these vascular responses.

Main Methods:

• Measurements of wattle blood flow (Q) and vascular resistance (R) in unanesthetized chickens.
• Application of local and general heating stimuli.
• Pharmacological interventions including beta-stimulation (isoproterenol), alpha-blockade (phenoxybenzamine), cholinergic blockade (atropine sulfate), and beta-adrenergic blockade (propranolol).

Main Results:

• Both local and general heating increased wattle blood flow (Q) and decreased vascular resistance (R).
• Heating-induced responses were reversed upon termination of heating.
• Beta-stimulation reduced vascular resistance and increased blood flow, indicating beta receptors.
• Alpha-blockade caused vasodilation, suggesting tonic alpha-sympathetic tone.
• Cholinergic and beta-adrenergic blockade did not alter the vascular response to general heating.

Conclusions:

• Wattle vasodilation during heating is primarily mediated by the release of alpha-sympathetic tone.
• The wattle vasculature possesses both beta receptors and tonic alpha-sympathetic innervation.