Blockade of hippocampal nicotinic receptors impairs working memory but not reference memory in rats.

In a three-panel runway task, intrahippocampal injection of the nicotinic receptor antagonist, mecamylamine (10 and 18 micrograms/side), significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points) in a test of working memory. This increase in errors also occurred after rats were given IP mecamylamine (10 mg/kg). Mecamylamine did not affect the number of errors in a test of reference memory whether it was given at doses up to 18 micrograms/side intrahippocampally or up to 10 mg/kg IP. These results suggest that mechanisms mediated by hippocampal nicotinic receptors play a role in working memory but not in reference memory.