Electroconvulsive shock elicits wet-dog shakes and face washing in preweaning rats

Abstract

During the description of the ontogeny of electroshock seizures in rats, electroshock intensities from 5 to 500 mA were used and rats were tested at 17 ages between 1 and 21 days and at 30 and 60 days of age. Wet-dog shakes (WDS) and face washing grooming movements (FW) were observed following electroconvulsive shock (ECS) in preweaning but not in 30- or 60-day-old rats. Both behaviors appeared during postseizure depression with predictable post-shock latencies which decreased progressively with increasing age. WDS typically followed clonic convulsions. During their period of peak occurrence, 8 through 13 days of age, 30 to 60% of rats that exhibited clonus also showed a WDS, with a mean post-shock latency of 30–33 sec. The ages of peak occurrence of ECS-induced WDS were similar to the ages of peak incidence of head-shaking or tremoring induced by cholinergic or catecholaminergic drugs, as described previously. The mean stimulus for elicitation of WDS, approximately 400 mA during the first postnatal week, declined to approximately 30 mA during the third week. FW typically followed tonic convulsions. During their period of peak occurrence, 12 through 17 days of age, 50 to 75% of rats that exhibited a tonic seizure without hindlimb extension also showed FW, with a mean post-shock latency of 25–32 sec. The mean stimulus for elicitation of FW was also approximately 400 mA during the first postnatal week and declined with development but remained above intensities eliciting WDS. WDS and grooming have been associated with the actions of opiates, endogenous opioid peptides and related compounds. In our study these behaviors followed ECS at a time coincident with a previous description of post-ECS release of endogenous opioids in adult rats. Additional behaviors related to the effects of endogenous opioids and which follow electroconvulsive shock are also described. The present observations may be explained by release of endogenous opioids and related peptides by ECS either during seizures or during postseizure depression and perhaps by activation of developing cholinergic and monoaminergic systems.