Background: In spite of recent enrichment of neurochemical and
behavioural data establishing a neuroprotective role lot lithium, its
primary effects on cognitive functioning remain ambiguous. This study
examines chronic lithium effects on spatial working memory and long-term
retention.
Methods: In three discrete experiments, rats subjected to 30 daily
intraperitoneal injections (2 mmol/kg) of lithium (lithium groups: serum
lithium = 0.5 +/- 0.4 mEq/l, 12 h post-injection) or saline (controls)
were trained in 0-s delay T-maze alternation and then tested in 30-, 45-
and 60-s delay alternation (Experiments 1, 2, 3, respectively). Animals
from Experiment 1 were further tested in one-trial step-through passive
avoidance under mild shock parameters (0.5 mA, 1 s). Retention was
assessed 6 h later. Daily lithium or saline injections continued
throughout behavioural testing.
Results: Lithium animals were indistinguishable from controls during
0-delay alternation baseline (Experiments 1-3. accuracy > 88%) but
showed significantly higher accuracy than controls at 30- and 45-s
delays (93% versus 85% and 92% versus 82%, Experiments 1 and 2,
respectively). At 60-s delay (Experiment 3) this beneficial effect of
lithium was no longer apparent (lithium and control accuracy = 78%). In
Experiment 4, the shock used did not Support 6-h passive avoidance
retention in controls, whereas lithium animals showed significant
step-through latency increases.
Conclusions: Chronic lithium enhanced spatial working memory and
promoted long-term retention of a weak aversive contingency. The results
suggest that lithium may have potential as a cognitive enhancer. (c)
2006 Elsevier B.V. All rights reserved
