Plasma nicotine, plasma beta-endorphin and mood states during periods of chronic smoking, abstinence and nicotine replacement.
Nicotine is known to release neuroendocrine substances which may subsequently reinforce smoking behavior by improving mood states. The purpose of this study was to examine changes in plasma beta-endorphin and mood states during periods of chronic smoking, abstinence from smoking, and abstinence while chewing nicotine gum. A modified A-B-A-C design was used. Normal male volunteers were randomly assigned to an experimental or control group. Over a 12-day protocol, experimental subjects smoked ad libitum for 2 days, were abstinent for 4 days, resumed smoking for 2 days, and then chewed nicotine gum for the final 4 days. Control subjects smoked ad libitum throughout the entire protocol. Results indicated that changes in plasma beta-endorphin levels were not related to changes in the four smoking conditions. Plasma nicotine and mood states were related, such that dysphoric moods increased during abstinence from smoking in comparison to the control group. To investigate further the relationships between nicotine, beta-endorphin and reinforcement for smoking, it may be necessary to characterize endogenous opioid peptide release in the central nervous system during smoking.