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Recurrent and reciprocal inhibition of the human monosynaptic reflex shows opposite changes following intravenous administration of acetylcarnitine

1991; Wiley; Volume: 143; Issue: 1 Linguagem: Inglês

10.1111/j.1748-1716.1991.tb09198.x

1365-201X

Marco Schieppati, I. Gritti, Corrado Romano,

Neurobiology and Insect Physiology Research

A long‐latency, long‐lasting increase in the recurrent inhibitory effect on the coleus monosynaptic (Hoffmann, H) reflex was induced after intravenous administration of L‐acetylcarnitine, a substance known to possess central cholinergic activity. This effect was paralleled by disappearance of the H reflex inhibition (functionally disinhibition) induced by stimulation of Ia afferent fibres from the tibialis anterior (reciprocal inhibition) and gastrocnemius medialis muscle. Magnitude and time course of the L‐acetylcarnitine‐induced effects were significantly correlated. The data suggest that (1) the L‐acetylcarnitine depression of the reciprocal inhibition is mediated by excitation of Renshaw cells impinging on la interneurones (INs), and (2) the inhibitory effect of GM Ia afferents onto Sol is mediated by INs subjected to Renshaw inhibition. The results point to the similarity in the wiring of the ‘output stage’ circuit between cat and humans, and provide a method for testing this network in man.