Chronic Nicotine Self-Administration Augments Hypothalamic–Pituitary–Adrenal Responses to Mild Acute Stress

We investigated the effect of chronic nicotine self-administration (SA) on hypothalamic–pituitary–adrenal (HPA) hormonal responses to acute stressors. Adult male Sprague–Dawley rats were given access to nicotine (0.03 mg/kg) for 23 h per day for 20 days. On day 1 of acquisition of nicotine SA, plasma levels of both adrenocorticotropin and corticosterone were significantly increased 15–30 min after the first dose of nicotine. These hormonal changes were no longer significant on day 3, when adrenocorticotropin levels were