Nicotine Tolerance in Chromaffin Cell Cultures: Acute and Chronic Exposure to Smoking‐Related Nicotine Doses

Abstract:Nicotine tolerance and dependence are key aspects of tobacco addiction; however, the cellular mechanisms underlying these phenomena are poorly understood. Adrenal chromaffin cells release catecholamines upon exposure to nicotine and with repeated exposure this response exhibits nicotine tolerance. Using bovine adrenal chromaffin cells in culture, we have demonstrated acute and chronic nicotine tolerance at doses relevant to that in the blood and tissues of smokers (10–7Mto 10–6M). Chromaffin cells are preexposed to low doses of nicotine for time periods ranging from 10 min to 7 days and then subsequently challenged with a maximally stimulating dose of nicotine (10–5M) for 10 min, all at 37°C. Preexposure to nicotine results in a depression of45Ca uptake and catecholamine release upon subsequent nicotine challenge. Acute tolerance or desensitization of nicotinestimulated catecholamine release begins to occur in minutes after preexposure to 10–6Mnicotine at 37°C. The depression of catecholamine release upon preexposure to nicotine is both dose and temperature dependent and is not seen with potassium‐evoked release. Chronic exposure to 10–7Mnicotine for 3 days led to a depression of the secretory response to ∼70% of control responses. There was a trend toward recovery of full response by days 5 and 7 of 10–7Mnicotine preexposure. Nearly complete depression of the nicotine‐evoked release occurs within the first day of exposure to 10–6Mnicotine and persists for at least a week of nicotine exposure at 37°C. Nicotine tolerance in the catecholamine release response was reversible after nicotine washout. Cross‐tolerance between nicotine, acetylcholine, and dimethylphenylpiperazinium was observed after 5 days’exposure to one agonist and subsequent challenge with a different agonist. Acute tolerance is likely to be related to nicotinic receptor desensitization. The mechanisms of chronic tolerance and potential adaptive cellular changes remain to be determined.