Fig. 10.   Inhibition of DNA synthesis in rat brain regions after a single dose of nicotine (McFarland et al., 1991; Slotkin, 1992; Tolson et al., 1995). Measurements of [³H]thymidine incorporation into DNA were made in the first 30 min after nicotine administration. Susceptibility is directly related to the concentration of nicotinic cholinergic receptors in each region, namely brainstem  forebrain > cerebellum. CON, control; NIC, nicotine. ANOVA, analysis of variance; CON, control; NIC, nicotine.