<p>The eigenvalue of the Pink module was significantly correlated with nicotine intake (A) but its correlation with food reward earned was not significant (B), suggesting behavioral specificity of the module. Nnat contributed strongly to the expression characteristics of the Pink module (C). The expression pattern of Nnat across the 10 strains measured by PCR showed significant correlation with nicotine intake (D). Strains: BN: Brown Norway, DA: Dark Agouti, F344: Fisher 344, Lew: Lewis, SHR: Spontaneous hypertensive rat, WKY: Wistar-Kyoto. For the F1 hybrids, the two letters representing the initials of the maternal and paternal strains were used.</p
