Sympathetic control of nasal blood flow in the rat mediated by alpha(1)-adrenoceptors.
Experiments were undertaken, using laser-Doppler flowmetry, to determine the nature of adrenoceptors mediating sympathetic nerve evoked nasal vasoconstrictor responses in anesthetized rats. Presence of sympathetic tone was confirmed by a large (330%) increase of nasal blood flow following section of the ipsilateral preganglionic cervical sympathetic nerve. Electrical nerve stimulation produced reproducible, frequency-related nasal vasoconstrictor responses with near maximal response, observed at less than 10 Hz. Evoked nasal vasoconstrictor responses were largely blocked with intravenous treatment with the non-selective alpha-adrenoceptor antagonists, phentolamine (5 mg kg(-1)) and phenoxybenzamine (2 mg kg(-1)), as well as with the selective alpha(1)-adrenoceptor antagonist, prazosin (300 microg kg(-1)). alpha(2)-Adrenoceptor antagonism with rauwolscine (500 microg kg(-1)) potentiated neurally evoked nasal vasoconstriction. Neither atropine (1 mg kg(-1)) nor propranolol (1 mg kg(-1)) altered the evoked responses. Rats with intact cervical sympathetic nerves responded to rauwolscine with a modest constriction. Subsequent prazosin administration produced an increase of nasal blood flow of approximately 275%. These results suggest that the nasal vasculature of the rat is under intense sympathetic tone and that the resulting neurogenic vasoconstriction is mediated exclusively by activation of alpha(1)-adrenoceptors.
Department of Biosciences, Teikyo University of Science and Technology, Yamanashi, Japan
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Kawarai
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Koss
D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005728:Ganglia, Sympathetic / Q000187:drug effects / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D008297:Male; D009296:Nasal Cavity / Q000187:drug effects / Q000502:physiology; D009297:Nasal Mucosa / Q000098:blood supply / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism*; D010643:Phenoxybenzamine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D010643:Phenoxybenzamine; D015016:Yohimbine; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine