title: Effects of (+)-methamphetamine on path integration and spatial learning, but not locomotor activity or acoustic startle, align with the stress hyporesponsive period in rats.
abstract: Rats treated with (+)-methamphetamine (MA) on postnatal days (P) 11-20 exhibit long-term spatial and path integration (Morris water maze (MWM) and Cincinnati water maze (CWM)) learning deficits whereas those treated on P1-10 do not. MA treatment increases corticosterone release in an age-dependent U-shaped pattern that corresponds to the stress hyporesponsive period (SHRP; P4-15). Here we tested the hypothesis that the cognitive effects induced by MA are associated with treatment that begins within the SHRP. Three treatment regimens were compared, P1-10, P6-15, and P11-20. One male/female pair/litter received 0, 10, or 25mg/kg MA/dose (four doses/day at 2h intervals given s.c. with 19-21 litters/regimen). Locomotor activity and acoustic startle were tested as behaviors not predicted to be associated with the SHRP. Cincinnati and Morris water maze findings were consistent with the hypothesis in that MA-treated animals exposed from P6-15 or P11-20 showed impaired learning compared to those exposed from P1-10; however, on probe trials in the Morris water maze, MA-induced memory impairments were not regimen-specific and were contributed to by all treatment regimens. All MA treatment regimens induced reductions in locomotor activity and acoustic startle facilitation as expected. No differential effect on prepulse trials was seen suggesting no impairment in sensory gating. Cognitive deficits from neonatal MA treatment are associated with the SHRP and may be the product of hypothalamic-pituitary-adrenal (HPA) axis dysregulation during critical periods of brain development.
authors.affiliation: Division of Neurology, Department of Pediatrics, Cincinnati Children's Research Foundation and University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. charles.vorhees@cchmc.org
authors.forename: Charles V
authors.initials: CV
authors.lastname: Vorhees
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Skelton
authors.forename: Curtis E
authors.initials: CE
authors.lastname: Grace
authors.forename: Tori L
authors.initials: TL
authors.lastname: Schaefer
authors.forename: Devon L
authors.initials: DL
authors.lastname: Graham
authors.forename: Amanda A
authors.initials: AA
authors.lastname: Braun
authors.forename: Michael T
authors.initials: MT
authors.lastname: Williams
mesh_terms: D000293:Adolescent; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003071:Cognition / Q000187:drug effects; D005106:Exploratory Behavior / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008694:Methamphetamine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009483:Neuropsychological Tests; D011247:Pregnancy; D051381:Rats; D013216:Reflex, Startle / Q000187:drug effects*; D013037:Spatial Behavior / Q000187:drug effects*; D013312:Stress, Physiological; D013550:Swimming; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine