NOREPINEPHRINE IN MOUSE SPLEEN SHOWS MINOR STRAIN DIFFERENCES AND NO DIURNAL-VARIATION

Strain differences have been invoked to explain differing results when studying neural-immune interactions in laboratory animals. We investi gated the splenic norepinephrine (NE) content and concentration in thr ee strains of male mice (BALE/ C, C57BL/6, and DBA/Z), as well as poss ible diurnal variability in this innervation. Diurnal plasma corticost erone levels served as a positive control. Mice were housed on a 12 h on/12 h off light/dark cycle for 3 weeks, then sacrificed at one of si x times during the 24 h cycle. Spleen NE total content and concentrati ons were determined using high performance liquid chromatography with electrochemical detection. We found small but significant differences between strains in total resting spleen NE content (BALB/C > C57BL/6 > DBA/Z) and in resting NE concentration (C57BL/6 > BALB/C > DBA/2). Th is may reflect differences in spleen weight (BALB/C > DBA/2 > C57BL/6) . The expected diurnal pattern of plasma corticosterone was seen in al l strains, but no diurnal differences were found in NE content or conc entration.