Physical activity correlates with glutamate receptor gene expression in spinally-projecting RVLM neurons: a laser capture microdissection study

Abstract

Physical inactivity is an important risk factor in the development of cardiovascular disease. The rostral ventrolateral portion of the medulla (RVLM) is composed of heterogeneous populations of neurons that are involved in the regulation of the cardiovascular system. Because of functional heterogeneity, studying the changes in the gene expression of this specific population of neurons within the RVLM is challenging. In the present study, a fluorescent retrograde tracer was injected into the spinal cord to specifically label bulbospinal RVLM neurons in sedentary and active rats. Laser capture microdissection (LCM) was then employed to collect the fluorescently labeled neurons from sections encompassing the rostrocaudal extent of the RVLM. RNA extracted from the neurons was used in qRT-PCR analysis. Changes in gene expression levels of glutamate and GABA receptor subunits were compared between sedentary and physically active rats. GLUR3 subunit showed a significant negative correlation between total running distance and its relative gene expression in active rats. There were no significant difference in the gene expression of NMDA (NR1, NR2A, NR2B, NR2C and NR2D), AMPA (GLUR1, GLUR2 and GLUR3) and GABAA (GABAA1 and GABAA2) receptor subunits. Overall, the present study demonstrates the feasibility of utilizing LCM to investigate the gene expression changes in a specific population of neurons in the RVLM. Correlation studies suggest that physical activity could contribute to neuroplasticity in the RVLM.

Keywords: Laser capture; Microdissection; Physical activity; RVLM; Retrograde tracer; Sedentary; Spinally-projecting; qRT-PCR.