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

Abstract

1 The e ects 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 (248 ± 418C). 2 Transmural electrical stimulation (1 ± 8 Hz, at supramaximal voltage) produced frequency-dependent contraction, and this response, partially blocked by tetrodotoxin (1 mM) and phentolamine (1 mM), was reduced by cooling (308C ± 248C) and was not modi®ed by warming (418C), as compared to that recorded at 378C. 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 (348C ± 248C) than at 378C or warming (418C). 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 (348C ± 248C), but not at 378C or warming (418C). 5 Pretreatment with angiotensin II (0.1, 0.3 and 1 mM) 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.

Effect of neuropeptide Y on the sympathetic contraction of the rabbit central ear artery during cooling

“…At 37°C, we found that NPY potentiates the contraction of rabbit ear arteries evoked by sympathetic stimulation, confirming previous observations made in our laboratory [24]. This agrees with other studies showing that NPY potentiates the sympathetic response in guinea-pig saphenous artery [4], rat femoral and mesenteric arteries [26] and rabbit ear and saphenous vein [18].…”

“…The present results show that, during cooling, NPY potentiates the contraction of rabbit ear arteries in response to electrical stimulation more at 30°C than at 37°C, and confirm previous results from our laboratory [24]. This difference between the effects at 30°C and 37°C is not probably due to the lower initial contractions produced by electrical stimulation at 30°C, because the greater effect of NPY at 30°C persists when stimuli producing similar initial contractions are compared.…”

“…The temperature of the bath was adjusted from the beginning of the experiment to 37°C or 30°C (cooling), and the arteries remained at the chosen temperature for the duration of the experiment. This temperature of 30°C was chosen to study the effects of cooling, because previous studies have shown that it produces clear differences in the vascular response compared with 37°C [24], and it is a temperature that may occur in the skin of the rabbit ear in physiological conditions [11].…”

“…This issue is interesting because the cutaneous circulation is mainly regulated by sympathetic adrenoceptor mechanisms and is involved in body temperature regulation [19]. In a previous study from our laboratory, using the rabbit central ear artery as a model of cutaneous arteries, we found that NPY potentiates the in vitro response to electrical stimulation to a greater extent during moderate cooling (30°C) than at normal temperatures [24]. Some cutaneous arteries, such as the rabbit central ear artery [20,28] and the rat tail artery [32], have a dense sympathetic innervation and these nerves contain noradrenaline and ATP as neurotransmitters, together with a relatively large quantity of NPY.…”

Cold-acclimation leads to differential regulation of the steelhead trout (Oncorhynchus mykiss) coronary microcirculation

“…Increased potency of ET-1 with cold exposure has also been shown in mammals. Low temperature increased the concentration-dependent constriction of rabbit ear vessels by ET-1 (81).…”