Social Isolation Effect on Nicotine Consumption in Adolescent Mice
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Ko, Ji-Hye
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Abstract
Adolescence is a period of increased vulnerability to nicotine addiction and a time when sensation seeking reaches its maximum value. Since the developmental trajectories of sensation seeking and impulse control are different, there are higher chances of risk-taking behaviors during that period. Also, adolescence is a period of being hypersensitive to rewards, especially the salience of social cues. Therefore, social context becomes a significant influence on drug use and abuse. This thesis describes the effects of social isolation on nicotine consumption in mid-adolescent mice who consumed nicotine voluntarily starting at postnatal day 40. We previously reported that nicotine consumption in socially isolated mice who started to consume nicotine at postnatal day 30 was significantly higher than in pair-housed mice, especially in males. Here, we extend our experiments to mid-adolescent mice, as well as Cd81 -/- mice (whose nicotine consumption increased significantly in both adults and early-adolescents). We also tested for the effects of estrous cycle on nicotine consumption in early adolescent females (starting on postnatal day 30). After the nicotine self selection, behavioral and emotional sings of withdrawal were measured. Here, we report that mid-adolescent nicotine consumption was increased by Cd81 loss-of-function in females, but not in males. After 24 h of nicotine abstinence, behavioral withdrawal signs were not significant and/or were decreased. In tests of emotional behavior, mice did exhibit emotional changes after 24 hr of nicotine abstinence, and these emotional changes appeared to be influenced by previous pair- vs. single-housing conditions. In early-adolescence, females began their estrous cycles around postnatal day 40, and their nicotine consumption was the lowest at the estrus stage (when estrogen levels are the lowest), and the highest during late metestrus/diestrus stage (when estrogen level starts to increase).
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Keywords
Adolescence, Nicotine addiction, Social isolation, CD81, Estrous cycle, Nicotine withdrawal