Peptidergic modulation of the sympathetic contraction in the rabbit ear artery: effects of temperature

Abstract

1. The effects of neuropeptide Y, endothelin-1, arginine-vasopressin and angiotensin II on the vascular contraction to sympathetic nerve stimulation were studied in isolated segments, 2 mm long, from the rabbit central ear artery, a cutaneous vessel, during changes in temperature (24°–41°C).

2. Transmural electrical stimulation (1–8 Hz, at supramaximal voltage) produced frequency-dependent contraction, and this response, partially blocked by tetrodotoxin (1 μM) and phentolamine (1 μM), was reduced by cooling (30°C–24°C) and was not modified by warming (41°C), as compared to that recorded at 37°C.

3. Pretreatment with neuropeptide Y (10, 30 and 100 nM) increased in a concentration-dependent manner the vascular contraction to sympathetic stimulation at every temperature studied, but this potentiation was greater during cooling (34°C–24°C) than at 37°C or warming (41°C).

4. Pretreatment with endothelin-1 (3 and 10 nM) or vasopressin (0.1, 0.3 and 1 nM) increased in a concentration-dependent manner the vascular contraction to sympathetic stimulation during cooling (34°C–24°C), but not at 37°C or warming (41°C).

5. Pretreatment with angiotensin II (0.1, 0.3 and 1 μM) did not modify the contraction to sympathetic stimulation at any temperature studied.

6. These results suggest that neuropeptide Y, endothelin-1 and vasopressin, but not angiotensin II, modulate the cutaneous vasoconstriction to sympathetic nerve stimulation by potentiating this vasoconstriction during cooling.

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