ACETYLCHOLINESTERASE INHIBITION AUGMENTS THE SYMPATHETIC NEURAL RESPONSE TO POSTURAL STRESS

Abstract

Muscle sympathetic nerve activity characteristics of burst frequency, mean burst amplitude and total amplitude were assessed during graded head-up tilt (HUT) (5 min each at 0, 20, 40 and 60°) before and 60 min following either an oral dose of pyridostigmine (60 mg; n = 9) or placebo (n = 5). No drug side effects were noticed. Burst frequency and total amplitude increased during HUT for both groups in both conditions. For the placebo group the increases in burst frequency, mean burst amplitude and total amplitude were not different in the repeated trials. However, following pyridostigmine burst frequency was elevated at rest (P < 0.05) and this elevation was sustained during HUT (main effect; P < 0.003). Similarly, mean burst amplitude (P < 0.004) and total amplitude (P < 0.0001) were elevated following pyridostigmine (main effects of drug). No differences in the neural response to a cold pressor test were observed following the drug or placebo treatment. It was concluded that pyridostigmine treatment, at doses that do not produce cholinergic side effects, augmented the sympathetic postganglionic nerve response to orthostatic stress. (Supported by CSA, NSERC, NAG 9-1844 from NASA, R01 AG12227 and M01 RR10732 from NIH).