Enhanced Glutamatergic Inputs to Hypothalamic Presympathetic Neurons in Spontaneously Hypertensive Rats

Abstract

Glutamatergic inputs in the paraventricular nucleus (PVN) maintain the increased sympathetic activity in hypertension. In this study, we determined the synaptic mechanisms of increased glutamatergic inputs to presympathetic PVN neurons in spontaneously hypertensive rats (SHR). The spinally projecting PVN neurons were retrogradely labeled by injection of Fluospheres into the intermediolateral cell column of the spinal cord. The basal frequency of spontaneous and miniature glutamatergic excitatory postsynaptic currents (EPSCs) of labeled PVN neurons are significantly greater in SHR than that in WKY rats. The amplitude of EPSCs was not significantly different between WKY and SHR. Furthermore, the postsynaptic NMDA currents elicited by either electrical stimulation or puff application of NMDA are significantly higher in SHRs than in WKY rats. However, AMPA currents evoked by the electrical stimulation and puff application in were not different between WKY and SHRs. In addition, ionotropic glutamate receptors selective antagonists kynurenic acid, AP5, and CNQX significantly decreased the basal firing activity of labeled PVN neurons in SHR, but failed to alter the firing activity of the PVN neurons in WKY rats. Thus, the glutamatergic synaptic inputs to presympathetic PVN neurons are augmented and contribute to the elevated firing activity of the PVN neruons in SHR.