Gene expression of NMDA receptor subunits using laser capture microdissection in the rostral ventrolateral medulla (RVLM) of sedentary versus physically active rats.

Abstract

The RVLM is important in tonic and reflex control of blood pressure and sympathetic nerve activity (SNA). We have observed enhanced SNA responses in sedentary versus physically active rats after microinjection of glutamate in the RVLM. Changes in glutamate receptor gene expression in the RVLM may contribute to enhanced responses in sedentary rats. In order to test this hypothesis, active (voluntary running for 15–18 wks) and sedentary (no running) rats were injected with Fluorogold (5%) at spinal levels T9‐T10 (n=5 ea). Brainstems were cryosectioned at 8μm for laser capture microdissection of bulbospinal RVLM neurons. RNA was isolated to analyze changes in gene expression of NMDA receptor subunits (NR2A‐D) using RT‐PCR. Gene expression was normalized to a housekeeping gene (HPRT). Preliminary results suggest that expression of NR2A‐D is not different between groups. However, within active rats, total running distance was significantly correlated to NR2C gene expression (r2=0.87, p<0.05). These findings suggest that physical activity contributes to NR2C neuroplasticity in the RVLM. However further studies are needed to address whether NMDA receptor protein expression contributes to enhanced responses in sedentary rats. (R01HL096787; DC007733)