[Implication of spinal catecholaminergic pathways in sympathetic pressor responses].
The dense noradrenergic innervation of the sympathetic cell bodies in the intermediolateral column suggests a role of noradrenergic pathways in cardiovascular control. We have attempted to specifically lesion these pathways by injecting 6-hydroxydopamine (6-OHDA) into the tyrosine-hydroxylase containing bundle of the first cervical segment. We examined the sympathetic vasopressor responses (nasopharyngeal stimulation under methscopolamine and intracisternal graded bolus of angiotensin II) in baro-intact and sino-aortically denervated conscious rabbits, 3-4 weeks after 6-OHDA or vehicle injections into the first cervical segment. At this time spinal cord noradrenaline was markedly reduced, particularly at segments closest to the injection site. Injections caused little non-specific damage and had no effect on spinal cord serotonin levels. The 6-OHDA treated animals demonstrated marked attenuation of the pressor responses to nasopharyngeal stimulation (27 p. 100, p less than 0.001) and to intracisternal angiotensin after sino-aortic denervation (delta ED50 = 3.1 log units, p less than 0.001). We conclude from these studies that the descending catecholamine pathways participate in sympathetic vasoconstriction following nasopharyngeal stimulation or stimulation of central angiotensin II receptors. However these effects are normally inhibited by baro-reflex mechanisms.
D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002946:Cisterna Magna / Q000187:drug effects; D003714:Denervation; D019832:N-Methylscopolamine; D009305:Nasopharynx / Q000187:drug effects; D009638:Norepinephrine / Q000502:physiology*; D011817:Rabbits; D012602:Scopolamine Derivatives / Q000008:administration & dosage / Q000494:pharmacology; D012850:Sinus of Valsalva / Q000294:innervation; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects
D012602:Scopolamine Derivatives; D000804:Angiotensin II; D019832:N-Methylscopolamine; D009638:Norepinephrine
Implication des voies catécholaminergiques spinales dans les réponses pressives sympathiques.