Nicotine's primary metabolite supports learning and memory by amplifying the action of a primary chemical messenger involved in both, researchers report. Nicotine has long been known to aid learning and memory, but it's also highly addictive with a host of side effects from nausea and vomiting to increasing blood pressure and heart rate. The side effects reflect nicotinic receptors' presence in other areas of the brain and body and explain why its therapeutic use has essentially been limited to helping smokers quit, one researcher said.