Fig. 5.

Quantitative analysis of anti-nAChRα4 immunoreactivity between young and aged CBA/J mice given nicotine in their water for 6 weeks or 11 months. The number of neurons stained for nAChRα4 immunoreactivity in the designated region was obtained from sections such as those shown in Figure 4 and was compiled from three mice in each group as described in the text. Error bars reflect the mean number (± SEM) of immunopositive cells in each region counted from at least eight sections for each animal. A, Stained neurons in the polymorphic area of the dentate gyrus from 25-month-old mice that were supplied nicotine for 11 months (chronic) versus aged mice (24–27 months old) either not given nicotine or administered nicotine for only 6 weeks (acute) were counted. The double asterisks denote a significant difference (p < 0.01). B, The number of immunopositive neurons observed in the CA1 region of each group was similarly scored. A significant decrease in the number of stained neurons in all aged groups relative to young animals (p < 0.01) was observed in this region of the hippocampus (see text).