Abstract
Microanalytic determinations of serotonin and norepinephrine were done on dissected portions of brain consisting of diencephalon, mesencephalon, and pons in two strains of mice, C57 bl/10 and BALB/c. The BALB/c strain had 1.34 µg of serotonin per gram of dissected brain, and the C57 bl/10 had 1.07 µg/g. This difference was statistically significant (P < 0.01). The levels of norepinephrine were not significantly different in the two strains (P > 0.25).