Plasticity in the myenteric plexus of the rat ileum after long-term sympathectomy.
To investigate the effect of chronic sympathectomy on the innervation of a tissue with an extensive intrinsic component, 1-week-old rat pups were treated with 50 mg/kg guanethidine for 3 weeks, a treatment shown to produce complete and long-lasting sympathectomy, and the ileum examined. Changes in the levels of noradrenaline, neuropeptide Y, calcitonin gene-related peptide, substance P and vasoactive intestinal polypeptide in the external muscle layers containing the myenteric plexus of the ileum were determined between 6 and 20 weeks of age. After sympathectomy, noradrenaline levels were initially depleted (3% of age-matched controls at 6 weeks, P < 0.001, and 18% of age-matched controls at 12 weeks, P < 0.001), but were not significantly reduced at 20 weeks (67% of age-matched controls). Such increases in noradrenaline content with time after sympathectomy did not occur in the mesenteric vein (levels in 20-week-old sympathectomized rats were 2% of the control values (P < 0.001). In the myenteric plexus, catecholamine fluorescent nerve fibers were seen in the 12-week-old sympathectomized rats, although tyrosine hydroxylase-immunoreactivity was absent. Guanethidine sympathectomy had no effect on the neuropeptide levels in 6-week-old rat ileum but there was a selective increase at 20 weeks; the levels of calcitonin gene-related peptide and substance P were increased (X3, P < 0.001 and X1.6, P < 0.05, respectively) while vasoactive intestinal polypeptide and neuropeptide Y levels were unchanged. Short-term sympathectomy (destruction of sympathetic nerve terminals by acute 6-hydroxydopamine treatment) had no affect on noradrenaline or peptide levels in this tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
D000320:Adrenergic Fibers / Q000201:enzymology; D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D006145:Guanethidine; D007082:Ileum / Q000201:enzymology / Q000294:innervation* / Q000378:metabolism; D007150:Immunohistochemistry; D009130:Muscle, Smooth / Q000201:enzymology / Q000294:innervation / Q000378:metabolism; D009197:Myenteric Plexus / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine; D051381:Rats; D017207:Rats, Sprague-Dawley; D013563:Sympathectomy, Chemical; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D009479:Neuropeptides; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase; D009638:Norepinephrine; D006145:Guanethidine