Alpha-adrenoceptor influence on plasma levels of neuropeptide Y-like immunoreactivity and catecholamines during rest and sympathoadrenal activation in humans.
Antecubital venous plasma neuropeptide Y-like immunoreactivity (NPY-LI) and catecholamines were analyzed in six healthy volunteers performing a graded bicycle exercise without medication and after acute administration of clonidine, phentolamine, and nifedipine. During the control exercise, plasma noradrenaline (NA), adrenaline (A), and NPY-LI increased to 17-, 7-, and 3-fold the resting values, respectively, at a maximal workload. Clonidine (300 micrograms p.o.) reduced resting and exercising heart rate (HR) and systolic blood pressure (SBP). Plasma NA at rest decreased and NA, A, and NPY-LI were 40-60% lower during the exercise after clonidine compared to the control. Phentolamine (0.07 mg X kg-1 every 10 min i.v.) and nifedipine (20 mg p.o.) increased HR and reduced SBP during the exercise. Plasma NA at rest was elevated threefold and the exercise-induced increases in NA and A were also enhanced after phentolamine. Plasma NPY-LI at rest was unchanged by phentolamine, while it was increased five-fold, as compared to the control, at the highest workload. Nifedipine slightly enhanced plasma NA and NPY-LI but not A during exercise. It is suggested that NPY is released mainly at high levels of sympathetic activity and that blood-pressure-lowering drugs acting on alpha adrenoceptors acutely influence the release of both NA and NPY-LI from sympathetic nerves in humans.
Pernow
J
J
Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Lundberg
J M
JM
Kaijser
L
L
D000311:Adrenal Glands / Q000502:physiology*; D000328:Adult; D002395:Catecholamines / Q000097:blood*; D003000:Clonidine / Q000494:pharmacology; D015444:Exercise; D006801:Humans; D008297:Male; D009478:Neuropeptide Y / Q000097:blood*; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood; D010646:Phentolamine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012146:Rest; D013564:Sympathetic Nervous System / Q000502:physiology*
D002395:Catecholamines; D009478:Neuropeptide Y; D011942:Receptors, Adrenergic, alpha; D009543:Nifedipine; D003000:Clonidine; D009638:Norepinephrine; D010646:Phentolamine