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Mechanisms contributing to the regional haemodynamic effects of neurotensin in conscious, unrestrained Long Evans rats
Author(s) -
Bachelard Hélène,
Gardiner Sheila M.,
Kemp Philip A.,
Bennett Terence
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14234.x
Subject(s) - phentolamine , neurotensin , medicine , bradycardia , endocrinology , tachycardia , propranolol , mesenteric arteries , heart rate , anesthesia , blood pressure , neuropeptide , artery , receptor
1 The regional haemodynamic effects of i.v. bolus doses of neurotensin (10–1000 ng) were assessed in conscious, unrestrained Long Evans rats chronically instrumented with miniaturized, pulsed Doppler probes. 2 Neurotensin caused increases in blood pressure, together with dose‐related tachycardias and constrictions in the renal, superior mesenteric and hindquarters vascular beds. The tachycardia elicited by the 1000 ng dose of neurotensin was preceded by a transient bradycardia. 3 In the presence of phentolamine, the pressor effect of neurotensin (1000 ng) was converted into a hypotensive effect, accompanied by reduced tachycardic and constrictor responses in the renal, superior mesenteric and hindquarters vascular beds. The tachycardia was not preceded by a bradycardia. 4 In the presence of phentolamine and propranolol, the pressor and bradycardic responses to neurotensin were unaffected, whereas the tachycardia was abolished. The renal vasconstrictor effect was smaller, while the constrictions in the superior mesenteric and hindquarters vasculars beds were not different from those in untreated rats. 5 In rats neonatally treated with capsaicin (50 mg kg −1 , s.c.), the pressor effects elicited by neurotensin (300 and 1000 ng) were reduced as were the constrictor responses in the renal (at the dose of 300 ng), superior mesenteric (at the dose of 300 ng) and hindquarters (at both doses) vascular beds. The bradycardia elicited by neurotensin (1000 ng) was absent, whereas the tachycardia was potentiated. 6 The results indicate that in conscious, intact rats neurotensin appears to exert cardiovascular influences through activation of sympathoadrenal mechanisms and also through non‐adrenergic effects on the heart, renal, superior mesenteric and hindquarters vascular beds. The latter effects appear to involve capsaicin‐sensitive nerves.