Tyrosine hydroxylase activity in the sympathoadrenal system under basal and stressful conditions: effect of 6-hydroxydopamine.
Subtotal destruction of central noradrenergic neurons with the neurotoxin, 6-hydroxydopamine, is known to increase tyrosine hydroxylase (TH) activity within surviving nerve terminals. The present report demonstrates a similar, dose-related elevation of TH activity in the adrenal medulla and sympathetic nerves after systemic 6-hydroxydopamine treatment. Two temporally distinct processes were observed in the sympathetic nerves: a rapid activation of TH, present during the first few days after the lesion, and a more gradual increase in maximal TH activity, most probably due to enzyme induction. In this regard, the stimulatory effect on catecholamine biosynthesis of cyclic AMP-dependent phosphorylation was attenuated substantially within cardiac sympathetic nerves 3 days after the lesion, but by 3 weeks the efficacy of cyclic AMP-dependent phosphorylation was restored completely. Similarly, the normal activation of cardiac TH activity elicited by insulin-induced hypoglycemia and cold stress was absent soon after 6-hydroxydopamine treatment, but returned 3 weeks later. These latter findings suggest that the adaptations within the sympathoadrenal system after subtotal sympathectomy can preclude further adaptations to stress.
Fluharty
S J
SJ
Rabow
L E
LE
Zigmond
M J
MJ
Stricker
E M
EM
D000313:Adrenal Medulla / Q000201:enzymology* / Q000294:innervation; D000818:Animals; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006321:Heart / Q000187:drug effects; D006892:Hydroxydopamines / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000201:enzymology; D013563:Sympathectomy, Chemical; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000201:enzymology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D006892:Hydroxydopamines; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase; D011494:Protein Kinases; D009638:Norepinephrine