Journal of Neurophysiology, Vol 50, Issue 5 1220-1235, Copyright © 1983 by APS
Dorsolateral pontine inhibition of dorsal horn cell responses to cutaneous stimulation: lack of dependence on catecholaminergic systems in cat
C. J. Hodge Jr, A. V. Apkarian, R. T. Stevens, G. D. Vogelsang, O. Brown and J. I. Franck
The effect of stimulating the dorsolateral pons (DLP) in the region of
locus ceruleus (LC) on lumbar dorsal horn cell responses to innocuous and
noxious cutaneous stimuli was assessed and the dependence of these effects
on intact pontospinal catecholaminergic systems was tested in
chloralose-anesthetized cats. DLP stimulation inhibited the responses of
dorsal horn cells to both noxious and innocuous skin stimuli. The
inhibitory effect was most prominent when the responses to noxious stimuli
were tested. The thresholds for eliciting DLP-spinal inhibition were lowest
(less than 30 microA) in the region of LC. The inhibitory effect was found
in both ipsilateral and contralateral dorsal horns. The DLP-spinal
inhibition was unaltered by depletion of spinal catecholamines brought
about by repeated lumbar intrathecal administration of 6-hydroxydopamine or
systemic administration of reserpine. We conclude that the DLP-dorsal horn
inhibition is not related to a catecholaminergic ceruleospinal system in
the cat and that the dependence of pain modulation by catecholamine systems
is a reflection of other descending pathways.
