enkephalin--ala(2)-mephe(4)-gly(5)- and Tachycardia

1. The cardiovascular effects of bilateral injection into the hypothalamic paraventricular nuclei of selective mu-, delta-, and kappa-opioid receptor agonists were investigated in conscious, unrestrained Wistar Kyoto rats, chronically instrumented with pulsed Doppler flow probes for measurement of regional haemodynamics. 2. The selective mu-agonist [D-Ala2,MePhe4,Gly5ol]enkephalin (DAMGO), injected bilaterally into the hypothalamic paraventricular nuclei (0.01-1.0 nmol), caused increases in blood pressure, tachycardias, vasoconstriction in renal and superior mesenteric vascular beds and substantial vasodilatation in the hindquarter vascular bed. 3. The administration of increasing doses (0.01-5.0 nmol) of the selective delta-agonist [D-Phe2,5]enkephalin (DPDPE) or the selective kappa-agonist, U50488H into the paraventricular nuclei (PVN) had no significant effect on blood pressure, heart rate, or regional haemodynamics. 4. Together, the present results are further evidence of a role for opioid peptides, especially acting at mu-receptors in the PVN, in the central regulation of the cardiovascular system, whereas a role for opioid peptides, acting at delta- and kappa-receptors in the PVN, seems less obvious from the present results.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Antihypertensive Agents; Blood Pressure; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Heart Rate; Hemodynamics; Hindlimb; Laser-Doppler Flowmetry; Male; Mesenteric Arteries; Microinjections; Paraventricular Hypothalamic Nucleus; Pyrrolidines; Rats; Rats, Inbred WKY; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Renal Artery; Tachycardia; Vasoconstriction; Vasodilation