from standard inbred strains of mice. The only substantial strain survey we could find was an old study from the laboratory of Donald Keith (Crabbe et al. 1983) that assessed resting pituitary beta-endorphin levels in 10 inbred strains that were also characterized for chronic withdrawal severity and drinking. Genetic correlations, however, were non-significant (*r*< 0.20). A few other studies reporting corticosterone levels studied too few mouse strains to make such analyses meaningful.
