New evidence for depression of depolarization of primary afferents by ammonium ions

Abstract

In experiments on cats, perfusion of the central canal of the lumbar segments of the spinal cord with artificial CSF with the addition of ammonium ions — depressed slow negative electrotonic dorsal root potentials (DRP). Depression of DRP developed parallel with depression of postsynaptic inhibition of monosynaptic reflexes, but it was not connected with depression of monoor polysynaptic reflex discharges. Subsequent perfusion of the central canal in normal CSF led to full recovery both of DRP and of inhibition of the test reflexes. It is suggested that depression of DRP by anmonium ions could be the result of blockade of the chloride pump, acting in afferent terminals and creating an emf for the outward transmembrane chloride current, producing depolarization of afferent fibers.