The Application of Sub-Perception Electrical Stimuli Elicits a Temporally Distinct Response from Restraint Stress: I. Antinociceptive Characteristics

Abstract

The antinociceptive action of a transcranially-applied, sub-perception, electrical stimulus was distinguished from the effect of mild restraint stress by comparing the temporal characteristics of the two analgesic responses in two experimental tests. Rats restrained in perspex tubes received either transcranial sub-perception electrostimulation treatment (TCET) at 12 μA, 10 Hz, or were sham-treated. Sham treatment for 5 or 10 but not 20, 40, 60 or 120 min produced an antinociceptive effect in the tail flick latency (TFL) test. The withdrawal latencies in the TFL test were significantly longer in the rats that received TCET while being restrained for 10, 20 and 40 but not 5, 60 or 120 min, compared with sham animals comparably restrained for the same periods of time. Rats restrained and receiving electrical stimuli for 20, 40 or 60 but not 5, 10 or 120 min exhibited a significantly decreased abdominal constriction (AC) response to intraperitoneal injection with hypertonic saline, compared with sham animals restrained for similar periods of time. These data indicate that the arousal induced by the obligatory handling and mild restraint produces a transient antinociceptive effect in the TFL test. Concomitant administration of a sub-perception current induced an antinociceptive effect which persisted and increased after the current had ceased. In the AC test, an antinociceptive effect was apparent only if the sub-perception current was administered, and this also increased after cessation of current.