Physiology Pulpal anodal blockade of trigeminal field potentials elicited by tooth stimulation in the cat

199

Pain, 2 (1976) 199-208 @ Elsevier/North-Holland,

Amsterdam

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PHYSIOLOGY

Pulpal anodal blockade lation in the cat

of trigeminal

field potentials

elicited by tooth

R.W. Fields, R.B. Tacke and B.S. Savara, Exp. Neurol.,

stimu-

47 (1975) 229-239

The blocking effect of anodal current on the excitability of the tooth pulp nerve was studied in cats anesthetized with b~biturates. Anodal direct blocking currents ranging from 50 to 60 PA were found to result in a reversible attenuation of the field potentials in the trigeminal nucleus evoked by monopolar or bipolar stimulation of the tooth pulp nerve. An induction time, inversely related to the blocking current and lasting up to several minutes, was required for the establishment of a new steady-state level of excitability. Higher intensities of blocking currents resulted in physiological changes that were immediately reversible.

Effects tract

of activity

A.G. Brown, 259

in non-myelinated

W.C. Hamann

afferent

fibres on the spinocervical

and H.F. Martin III, Brain Res., 98 (1975) 243-

Cutaneous C fibers excite spinocervical tract cells in unanesthetized decerebrate-spinal cats, but have no other effect on transmission through this system. Common inhibitory inter-neurons are suggested to act in the pathways from descending systems and cutaneous A and C fibers to the excitatory input to spinocervical tract cells. The finding that the C fiber input to the spinal cervical tract is of interest in the context of earlier evidence that nociceptive ascending pathways in the cat are localized in the dorsolateral funiculus of the spinal cord (Kennard, 1954).