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Effects of environmental enrichment on ERK 1/2 phosphorylation in the rat prefrontal cortex following nicotine‐induced sensitization or nicotine self‐administration
Author(s) -
Gomez Adrian M.,
Sun WeiLun,
Midde Narasimha M.,
Harrod Steven B.,
Zhu Jun
Publication year - 2015
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.12758
Subject(s) - nicotine , saline , sensitization , prefrontal cortex , chemistry , self administration , basal (medicine) , endocrinology , stimulation , medicine , pharmacology , cognition , immunology , psychiatry , insulin
Rats raised in an enriched condition ( EC ) exhibit alterations in the neurobiological and behavioral response to nicotine compared with rats reared in an impoverished condition ( IC ) or a standard condition ( SC ). The current study determined whether environmental enrichment differentially regulates extracellular signal‐regulated kinase1/2 ( ERK 1/2) activity in the prefrontal cortex in rats following nicotine sensitization or nicotine self‐administration. Under the saline control condition, EC rats displayed diminished baseline activity and greater sensitization to repeated administration of nicotine compared with IC and SC rats. After repeated saline injections, the basal levels of phosphorylated ERK 1/2 (p ERK 1/2) were higher in EC compared with IC and SC rats, which was negatively correlated with their respective baseline activities. Repeated nicotine (0.35 mg/kg) injections induced p ERK 1/2 to similar levels in SC and IC rats; however, the induction of p ERK 1/2 in EC rats by nicotine was not significantly different from saline controls, owing to their high baseline. In the self‐administration paradigm, EC rats self‐administered less nicotine (0.03 mg/kg/infusion) relative to IC or SC rats on a fixed ratio‐1 schedule of reinforcement. Accordingly, no differences in p ERK 1/2 were found between EC and IC rats self‐administering saline, whereas nicotine self‐administration resulted in an increase in p ERK 1/2 in IC rats but not in EC rats. Furthermore, the levels of p ERK 1/2 in EC and IC rats were positively correlated with their respective total number of nicotine infusions. Thus, these findings suggest that environmental enrichment alters the basal and nicotine‐mediated p ERK 1/2, which may contribute to enrichment‐induced behavioral alterations in response to nicotine.