Morehead State University

Poster Title

Effects of Blockade of Muscarinic Receptors and Nicotinic Receptors on Spatial Discrimination

Institution

Morehead State University

Abstract

Previous studies reported that blocking muscarinic receptors disrupts performance in spatial working memory task, and that performance impairment worsens when the delay period gets longer, suggesting that spatial working memory is sensitive to muscarinic receptor blockade. The present study compared the effects of muscarinic receptor antagonist (scopolamine) and nicotinic receptor antagonist (mecamylamine) on visuospatial discrimination using a spatial task without a delay component. Wistar rats were trained on a visuospatial task that required a correct barpress opposite to the cue location. Once the animals reached a behavioral criterion (>85% correct, 2 consecutive sessions), the drug phase began. On the day of testing, the animals received either a single dose of scopolamine (0.25-1.0 mg/kg, i.p.), mecamylamine (2.5-10mg/kg, i.p.), or saline in a counterbalanced manner. The same behavioral criterion (>85% correct, 2 consecutive sessions) was required between injections. We found that scopolamine disrupted correct responses in a dose-dependent manner and increased response latencies. Mecamylamine failed to affect correct responses. Our data are consistent with previous report that successful performance in spatial discrimination depends on activation of muscarinic receptors. Given the absence of a delay in our task, our results provide critical evidence that performance deficit after scopolamine reflects deficits in reference memory rather than working memory.

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Effects of Blockade of Muscarinic Receptors and Nicotinic Receptors on Spatial Discrimination

Previous studies reported that blocking muscarinic receptors disrupts performance in spatial working memory task, and that performance impairment worsens when the delay period gets longer, suggesting that spatial working memory is sensitive to muscarinic receptor blockade. The present study compared the effects of muscarinic receptor antagonist (scopolamine) and nicotinic receptor antagonist (mecamylamine) on visuospatial discrimination using a spatial task without a delay component. Wistar rats were trained on a visuospatial task that required a correct barpress opposite to the cue location. Once the animals reached a behavioral criterion (>85% correct, 2 consecutive sessions), the drug phase began. On the day of testing, the animals received either a single dose of scopolamine (0.25-1.0 mg/kg, i.p.), mecamylamine (2.5-10mg/kg, i.p.), or saline in a counterbalanced manner. The same behavioral criterion (>85% correct, 2 consecutive sessions) was required between injections. We found that scopolamine disrupted correct responses in a dose-dependent manner and increased response latencies. Mecamylamine failed to affect correct responses. Our data are consistent with previous report that successful performance in spatial discrimination depends on activation of muscarinic receptors. Given the absence of a delay in our task, our results provide critical evidence that performance deficit after scopolamine reflects deficits in reference memory rather than working memory.