Infant maternal separation, a paradigm of early life stress in rodents, elicits long-lasting changes in gene expression that persist into adulthood. In BALB/c mice, an inbred strain with spontaneously elevated anxiety and stress reactivity, infant maternal separation led to increased depression-like behavioral responses to adult stress and robustly increased editing of serotonin 2C receptor pre-mRNA. Chronic fluoxetine treatment of adult BALB/c mice exposed to early life stress affected neither their behavioral responses to stress nor their basal 5-HT 2C pre-mRNA editing phenotype. However, when fluoxetine was administered during adolescence, depression-like behavioral responses to stress were significantly diminished in these mice, and their basal and stress-induced 5-HT 2C pre-mRNA editing phenotypes were significantly lower. Moreover, when BALB/c mice exposed to early life stress were raised in an enriched postweaning environment, their depression-like behavioral responses to adult stress were also significantly diminished. However, their 5-HT 2C premRNA editing phenotype remained unaltered. Hence, the similar behavioral effects of enrichment and fluoxetine treatment during adolescence were not accompanied by similar changes in 5-HT 2C pre-mRNA editing. Enriched and nonenriched BALB/c mice exposed to early life stress also exhibited significantly increased expression of mRNA and protein encoding the G␣q subunit of G-protein that couples to 5-HT 2A/2C receptors. In contrast, G␣q expression levels were significantly lower in fluoxetine-treated mice. These findings suggest that compensatory changes in G␣q expression occur in mice with persistently altered 5-HT 2C pre-mRNA editing and provide an explanation for the dissociation between 5-HT 2C receptor editing phenotypes and behavioral stress responses.

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A new medium, which contained a chemically defined tissue culture base ("medium 199"), was developed for the cultivation of mycoplasmas. When supplemented with albumin, glucose, serum, and yeast extract, the new medium adequately supported the growth of Mycoplasma and Acholeplasma species.