title: Effect of stimulus intensity and number of treatments on ECS-related seizure duration and retrograde amnesia in rats.
abstract: BACKGROUND
  Animal models are frequently used to generate and test hypotheses about amnesia resulting from electroconvulsive therapy (ECT). Although many predictors of ECT-induced amnesia are known, their relative effects have been inadequately researched in the context of the animal models.
  
  
  OBJECTIVE
  We sought to determine the relative retrograde amnestic effects of electroconvulsive shock (ECS) stimulus intensity (dose) and number on strong memories in rats. We also sought to identify dose-dependent ceiling amnestic effects, if any.
  
  
  METHODS
  Adult rats (n = 144) were overtrained in a passive avoidance task using a step down apparatus. The rats were then randomized in a factorial design to receive one, two, or three once-daily bilateral ECS at 0-mC (sham ECS), 30-mC, 60-mC, 120-mC, or 180-mC doses. Recall of the pre-ECS training was assessed 1 day after the last ECS.
  
  
  RESULTS
  Retrograde amnesia was observed only in rats that received 3 ECS; dose-dependent amnestic effects did not emerge. Higher stimulus intensity was associated with a small (13%) but significant increase in motor seizure duration, but only at the first ECS; stimulus intensity did not influence the attenuation of seizure duration across repeated occasions of ECS.
  
  
  CONCLUSIONS
  With bilateral ECS, the number of ECSs administered is a more important variable than the ECS dose in weakening a strong, recently acquired, noxious memory; this finding may have important clinical implications. Higher stimulus intensity marginally increases motor seizure duration at the first ECS but does not influence the decrease in seizure duration across repeated ECSs.
authors.affiliation: Department of Psychopharmacology, National Institute of Mental Health and Neurosciences, Bangalore, India. andrade@nimhans.kar
authors.forename: Chittaranjan
authors.initials: C
authors.lastname: Andrade
authors.forename: S
authors.initials: S
authors.lastname: Thyagarajan
authors.forename: P S
authors.initials: PS
authors.lastname: Vinod
authors.forename: S N
authors.initials: SN
authors.lastname: Srikanth
authors.forename: N S K
authors.initials: NS
authors.lastname: Rao
authors.forename: J Suresh
authors.initials: JS
authors.lastname: Chandra
mesh_terms: D000648:Amnesia, Retrograde / Q000503:physiopathology*; D000818:Animals; D001245:Association Learning / Q000502:physiology; D001362:Avoidance Learning / Q000502:physiology; D004565:Electroconvulsive Therapy / Q000379:methods*; D004569:Electroencephalography; D006801:Humans; D008297:Male; D011939:Mental Recall / Q000502:physiology; D010056:Overlearning / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D012640:Seizures / Q000503:physiopathology*