Changes in regional vascular resistance in response to microinjection of L-glutamate into different antero-posterior coordinates of the RVLM in awakerats (vol 82, pg 137, 2000)

Changes in mean arterial pressure (MAP) and in regional vascular resistance (RVR, hindquarter, mesenteric and renal) induced by microinjection of L-gl utamate into three different antero-posterior coordinates of the rostral ve ntrolateral medulla (RVLM) [1200-1600 mum (n=10), 1601-2000 mum (n=12) and 2001-2500 mum (n=6) rostral to the obex] were investigated in unanesthetize d rats. Guide cannulas directed towards the RVLM were implanted 4 days prio r to the experiments. Doppler probes were implanted around the superior mes enteric, inferior abdominal aorta and left renal arteries and a catheter wa s inserted into the femoral artery and vein 1 day prior to the experiments. Insertion of the injector into the RVLM produced an increase in baseline M AP, which was back to control levels 2 min later, when L-glutamate was micr oinjected. Microinjection of L-glutamate (1 nmol/30 nl) into the three ante ro-posterior coordinates of the RVLM produced an increase in MAP associated with a similar increase in hindquarter, mesenteric and renal vascular resi stance, which were back to control 1 min later. Saline into the RVLM produc ed negligible effects on MAP and RVR. These findings suggest that the sympa thetic vasomotor neurons involved in the regulation of the regional vascula r resistance in rats are not topographically distributed in the antero-post erior coordinates of the RVLM. However, the experimental methods used to ev aluate the topographic distribution of sympatho-vasomotor neurons in the RV LM and the measurement of the regional blood flow may not be precise enough to detect any possible differences. (C) 2001 Elsevier Science B.V. All rig hts reserved.