The Journal of Neuroscience, June 15, 2000, 20(12):4732-4739
Adult Learning Deficits after Neonatal Exposure to
D-Methamphetamine: Selective Effects on Spatial
Navigation and Memory
Charles V.
Vorhees,
Sandra L.
Inman-Wood,
LaRonda L.
Morford,
Harry W.
Broening,
Masao
Fukumura, and
Mary S.
Moran
Division of Developmental Biology, Children's Hospital Research
Foundation and Department of Pediatrics, University of Cincinnati,
Cincinnati, Ohio 45229-3039
The effects of neonatal D-methamphetamine (MA)
treatment on cued and spatial learning and memory were investigated. MA
was administered to neonatal rats on postnatal days 11-20. All groups received four subcutaneous injections per day. Group MA40-4 received 40 mg · kg
1 · d
1 of
MA in four divided doses (10 mg/kg per injection). Group MA40-2 received 40 mg · kg
1 · d
1 of MA
in two divided (20 mg/kg/injection) and saline for the other two
injections per day. Controls received saline for four injections per
day. As adults, both MA groups showed no differences in swimming
ability in a straight swimming channel. The MA40-4 group showed no
differences in cued learning, but was impaired in hidden platform
learning in the Morris water maze on acquisition. They also showed
reduced memory performance on probe trials. Similar trends were seen on
reversal learning and reversal probe trials. Reduced platform-size
learning trials caused spatial learning impairments to re-emerge in the
MA40-4 group. The MA40-2 group showed no differences in straight
channel swimming, but was slower at finding the visible platform during
cued learning. They were also impaired during acquisition and memory
trials in the Morris hidden platform maze. They showed a similar trend
on reversal learning and memory trials, but were not different during
reduced platform-size learning trials. When the MA40-2 group's
performance on hidden platform learning and memory trials was adjusted
for cued trial performance, the spatial learning deficits remained. Deficits of spatial learning and memory are a selective effect of
neonatal methamphetamine treatment irrespective of other learning and
performance variables.
Key words:
methamphetamine; development; spatial learning; Morris
maze; rats; substituted amphetamines
Copyright © 2000 Society for Neuroscience 0270-6474/00/20124732-08$05.00/0