GABA, glutamate and taurine in the paraventricular nucleus (PVN) during the onset of renal wrap hypertension

Abstract

The PVN is involved in the development of renal wrap hypertension. We hypothesized that there is increased glutamate and reduced GABA neurotransmitter levels in the PVN during the onset of renal wrap hypertension (Day 7). PVN targeted microdialysis cannulae were stereotaxically placed unilaterally in sham and renal wrap rats one week prior to conscious microdialysis perfusion with artificial cerebrospinal fluid (aCSF) at a rate of 1ul/min for retrieval of perfusate for HPLC detection of GABA, glutamate and taurine. In addition to baseline, aCSF with the GABA uptake inhibitor, nipecotic acid (40 nM), and nipecotic acid (40 nM) plus veratradine (300 uM) were added to the perfusate. The rats were also instrumented with arterial femoral catheters for mean arterial blood pressure (MAP) and heart rate measures. MAP was significantly higher in renal wrap rats compared to sham [100 ± 8 vs. 128 ± 3 mm Hg (n=5–8); p≤0.05]. There were no differences in either PVN GABA or taurine levels. However, PVN glutamate levels were significantly greater in the perfusate throughout all treatments from renal wrap rats compared to sham (baseline: 46.87 ± 9.46 vs. 110.33 ± 17.72 ng/ml; nipecotic acid: 84.91 ± 20.76 vs. 196.97 ± 40.86 ng/ml; nipecotic acid + veratradine: 77.24 ± 17.46 vs. 236.72 ± 90.97 ng/ml). In conclusion there is enhanced basal glutamate as well as altered glutamate handling in the PVN during the onset of renal wrap hypertension.