Jw. Leem et al., INVOLVEMENT OF ALPHA(2)-ADRENOCEPTORS IN MEDIATING SYMPATHETIC EXCITATION OF INJURED DORSAL-ROOT GANGLION NEURONS IN RATS WITH SPINAL NERVELIGATION, Neuroscience letters, 234(1), 1997, pp. 39-42
The present study examined the effects of sympathetic stimulation on t
he activity of primary afferent neurons that had peripheral axons bein
g injured previously by a spinal nerve ligation. About 22% of afferent
s with injured fibers that showed spontaneous discharge were excited b
y sympathetic stimulation or systemic injection of adrenaline. Most sy
mpathetically-excited afferent neurons had axons that conducted in the
A-fiber range. This sympathetically-evoked afferent excitation was no
t affected by cutting the spinal nerve at a place close to the dorsal
root ganglion (DRG). Yohimbine, alpha(2)-antagonist, suppressed sympat
hetically-evoked afferent excitation which was not affected by alpha(i
)-antagonist prazosin. Clonidine, alpha(2)-agonist, exerted an excitat
ory effect, whereas oil-agonist phenylephrine had no effect on the act
ivity of afferents with injured fibers. No afferent fibers in control
preparations responded to sympathetic stimulation. The results suggest
that after a spinal nerve ligation, injured DRG neurons with fast-con
ducting fibers become sensitive to sympathetic activity via activation
of alpha(2)-adrenoceptors. (C) 1997 Elsevier Science Ireland Ltd.