Meeting Abstract
61.1 Sunday, Jan. 5 13:30 Size and neuronal density of midbrain regions in selectively bred high-runner mice THOMPSON, ZAL*; SHELTON, S; LEVIN, P; CLAGHORN, GC; GARLAND, JR, T; Univ. of Calif., Riverside; Humboldt State Univ.; Cal. State Univ., San Bernardino; Univ. of Calif., Riverside; Univ. of Calif., Riverside zthom002@ucr.edu
How does selection on a behavior alter brain structure? Previous studies showed that mice from 4 replicate high runner (HR) lines had increased total brain mass and increased midbrain volume (~13%), as compared with 4 non-selected control (C) lines, supporting the mosaic model of brain evolution. The midbrain includes several areas that are involved in locomotion and reward. The goal of the current research is to determine which areas within the midbrain have changed size in HR mice. Total wheel revolutions on days 5 and 6 of a 6-day wheel-running trial are used as the basis for selection in four HR lines. Four control (C) lines are bred without regard to wheel running. HR mice voluntarily run almost 3 times as far as C mice on a daily basis, primarily because they run faster. Female mice from generation 66 were housed without access to wheels for 8 weeks. Mice were then perfused, and their brains dissected and weighed. Brains were sliced into 40 micron coronal sections with a cryostat, Nissl stained, and photographed. ImageJ was used to outline and calculate the area of the substantia nigra (SN), periaqueductal gray (PAG), and red nucleus (RN) in relevant sections according to an atlas. Individual nuclei were counted with the help of the ITCN plugin for ImageJ. Nested ANCOVA in SAS Proc Mixed with body mass as a covariate showed larger total brain mass in HR lines but no statistical difference in either average areas or total neuronal counts for the SN or PAG. More areas will need to be analyzed to determine which are responsible for the enlarged midbrain volume in HR mice. In addition, HR and C mice with 8 weeks of wheel access will be compared, and 3D volume reconstructions of brain areas will be made, which should enhance our ability to detect differences. Supported by NSF IOS-11212732.
