Rate of rise of the cumulative depolarization evoked by repetitive stimulation of small-caliber afferents is a predictor of action potential windup in rat spinal neurons in vitro

• DOI: 10.1152/jn.1993.69.5.1621
• Publication Date: 2017-12-24T22:16:52Z
• Authors: L. G. Sivilotti; S. W. Thompson; C. J. Woolf
• Keywords: Caliber

1. The summation of depolarizing postsynaptic potentials (PSPs) evoked by stimulation primary afferent fibers in lumbar dorsal roots was studied and ventral horn neurons the rat hemisected spinal cord vitro with current-clamp intracellular recording techniques. PSPs activation A delta and/or C could summate after repetitive at low frequencies: this resulted a progressive, long-lasting change neuronal membrane potential (Vm) (cumulative depolarization). Cumulative depolarization not observed beta-fiber intensity or frequencies < 0.2 Hz. 2. Effective PSP resulting significant cumulative (> 5 mV) only if were longer than 4 s. On other hand, there no correlation between amplitude achieved neuron absolute duration resting properties (Vm input resistance). 3. With relation to changes Vm during train, three patterns response stimuli be detected both (DH) (VH) neurons: 1) little throughout train; 2) an initial depolarization, which either remained stationary decayed first 3-4 s stimulation; 3) progressive increasing train. 4. Depolarizing cell DC current injection steeper rise one half VH out nine DH tested. 5. Action windup, increase number action elicited each stimulus as train progresses, cells. C-fiber strength most effective eliciting windup. Windup associated responses belonging pattern. Indeed, depolarizations that windup had significantly slopes for trajectory those did not. In increased slope trajectory, also bring about 6. These results indicate that, although generation "slow" high-threshold afferents is necessary synaptic activity frequencies, rate pattern does depend on PSPs.(ABSTRACT TRUNCATED AT 400 WORDS)