Ethanol impairs behavioral strategy use in naive rats but does not prevent spatial learning in the water maze in pretrained rats.

RATIONALE: Ethanol impairs performance in the water maze in rats. A detailed behavioral analysis is required to fully evaluate the nature of the impairment. OBJECTIVES: A detailed behavioral analysis was carried out to evaluate the effect of ethanol on performance in the water maze task in male hooded rats given 2.0 or 6.0 g/kg ethanol by gavage. Multiple measures of water maze strategies learning and spatial learning were studied. METHODS: Water maze trials were recorded on videotape and digitized for offline analysis. Some rats were naive at the start of spatial training, whereas other rats received water maze strategies pretraining prior to spatial training to familiarize them with the general behavioral strategies required in the task. RESULTS: Naive ethanol-treated rats exhibited both spatial learning and water maze behavioral strategies impairments. There was no evidence of a spatial learning impairment that was independent of an associated behavioral strategies impairment. Further, ethanol impaired the ability of naive rats to swim to a stable visible platform. Pretrained ethanol-treated rats performed significantly better than naive ethanol-treated rats on almost all measures, and were indistinguishable from controls on most measures. CONCLUSIONS: These results suggest that ethanol may impair water maze performance in naive rats by interfering with their ability to acquire and use required water maze behavioral strategies and generate adaptive swim paths. Ethanol does not prevent robust spatial learning in rats that are familiar with required water maze behavioral strategies.

Complex behavioral strategy and reversal learning in the water maze without NMDA receptor-dependent long-term potentiation.

Successful performance of the water maze task requires that rats learn complex behavioral strategies for swimming in a pool of water, searching for and interacting with a hidden platform before its spatial location can be learned. To evaluate whether NMDA receptor-dependent long-term potentiation (NMDA-LTP) is required for learning the required behavioral strategies, rats with NMDA-LTP blocked by systemic pharmacological treatment were trained in the behavioral strategies using simplified and stepwise training methods. Despite the blockade of NMDA-LTP in the dentate gyrus and hippocampal area CA1, rats learned the required behavioral strategies and used them to learn both initial and reversed platform locations. This is the first evaluation of the role of NMDA-LTP specifically in behavioral strategy learning. Although hippocampal NMDA-LTP might contribute to the water maze task, this form of LTP is not essential for learning complex behavioral strategies or multiple hidden platform locations.

The effect of water maze spatial training on posterior parietal cortex transcallosal evoked field potentials in the rat.

Long-term potentiation (LTP) is the principal model of synaptic plasticity often used to explain the changes that occur in the brain as a result of learning and memory. In this experiment the relationship between rat posterior parietal cortex (PPC) transcallosal evoked field potentials (TCEPs) and spatial training in the water maze was examined to determine if LTP-like changes (i.e. learning-induced LTP) in PPC TCEPs occur as a result of spatial training. Spatial training consisted of 10 trials per day for 10 consecutive days. The location of the hidden platform was changed over the course of spatial training to ensure the rats' acquisition of several different platform positions. TCEPs were taken 1 and 23 h after each training session. Upon completion of all water maze training, the animals were administered LTP-inducing trains to ensure that the recording arrangement and procedure was capable of detecting LTP. The results showed that the rats quickly acquired the water maze task and that the recording arrangement and procedure were capable of detecting LTP, even after the first session of induction. However, despite robust place learning, the TCEPs taken after water maze training did not differ from those taken before water maze training. Although the present results failed to provide any evidence for a role of neocortical LTP in learning and memory, further studies of this nature are required to determine if the present results generalize to different behavioural tasks and/or cortical areas.

The effect of nonspatial water maze pretraining in rats subjected to serotonin depletion and muscarinic receptor antagonism: a detailed behavioural assessment of spatial performance.

A detailed behavioural analysis of water maze spatial performance in the rat was utilized to determine the effect of single and combined administration of p-chlorophenylalanine (PCPA; 1000 mg/kg, i.p.), an inhibitor of serotonin biosynthesis, and scopolamine hydrobromide (SCO; 1.0 mg/kg, i.p.), a muscarinic receptor antagonist. In some groups a water maze pretraining regimen known as non-spatial pretraining (NSP) was used to familiarize the animals with the general requirements of the task before spatial training was begun. The results showed that: (a) depletion of serotonin with PCPA had no effect on water maze performance and produced no sensorimotor disturbances; (b) antagonism of muscarinic receptors produced impairments in spatial and sensorimotor function in naive rats but neither effect was observed in rats first given NSP; (c) combined disruption of muscarinic and serotonergic function produced a severe deficit in spatial performance that was only partially alleviated by NSP; and (d) there was an association between poor maze acquisition scores and a high incidence of sensorimotor dysfunction. In addition to the water maze task the rats were also assessed for motoric performance on a beam walking test. The role of cholinergic and serotonergic systems in learning and memory is discussed.