SYMPATHETIC AND PARASYMPATHETIC INTERACTION IN VASCULAR CONTROL OF THE NASAL-MUCOSA IN ANESTHETIZED CATS

1. In cats anaesthetized with pentobarbitone sodium (45 mg kg(-1)), el ectrical stimulation of the parasympathetic nerve fibres to the nasal mucosa evoked frequency-dependent increases in nasal arterial blood fl ow whereas stimulation of the superior cervical sympathetic nerve indu ced marked vasoconstriction. 2. Sympathetic nerve stimulation for 3 mi n at 10 Hz evoked significant (P < 0.05) and prolonged (> 30 min) atte nuation of the vasodilatory response to subsequent parasympathetic sti mulation. 3. Combined pretreatment with adrenergic and cholinergic blo ckers reduced the vasoconstrictory effect of sympathetic stimulation b y 28 +/- 4% (mean +/- S.E.M.) and the parasympathetically evoked vasod ilatation by 20 +/- 5%. 4. The vasodilatory effects of exogenous vasoa ctive intestinal polypeptide, peptide histidine isoleucine and galanin , and the vasoconstrictory effects of exogenous neuropeptide Y (NPY) a nd alpha,beta-methylene adenosine 5'-triphosphate were not altered by adrenoceptor antagonists and atropine whereas the effects of exogenous noradrenaline and acetylcholine mere virtually abolished. 5. The atro pine-resistant parasympathetic vasodilatation remained significantly a ttenuated for more than 30 min after the non-adrenergic sympatheticall y evoked vasoconstriction. 6. Exogenous NPY (25 x 10(-9) mol) mimicked the effect of sympathetic stimulation in attenuating subsequent paras ympathetically evoked vasodilatation.