The components of SAP signals of low- frequency (LF: 0.08-0.15 Hz) and very low- frequency (VLF: 0.00-0.08 Hz) related with vasomotor tone that reflects the activity of sympathetic premotor neuron in the nucleus reticularis ventrolateralis (NRVL). The Sprague-Dawely male rats with acute endotoxemia (lipopolysaccharide, LPS; 15 mg/Kg i.v.) induced a reduction phase (phase¢¹), followed by partial recovery (phase¢º) and a secondary decrease (phase ¢»). The rats with acute endotoxemia display three phases based on change in the power density of LF and VLF component. Pretreatment with microinjection of NMDA receptor antagonist, MK-801, and non-NMDA receptor antagonist, CNQX into the bilaterial NRVL prolong the survival time and prolong the duration time of phase¢º and phase¢». Pretreatment with high concentration MK-801 (200 pmol) and CNQX (10 pmol) hold the MSAP and heart rate in the steady state and decrease the slope of MSAP falling during endotoxemia.The power density of pretreatment with high concentration MK-801 (200 pmol) and CNQX (10 pmol) was deceease. We conclude that the rat during experimental endotoxemia decrease the duration time of NMDA and non-NMDA receptor activity in NRVL. The NMDA receptor and non-NMDA receptor activity in NRVL during endotoxemia contribute the slope of MSAP falling and cause to death.

In this study, we investigated the role of angiotensinergic neurotransmission at nucleus reticularis ventrolateralis (NRVL), and the subtype of angiotensin receptors involved, during experimental endotoxemia induced by E. coli lipopolysaccharide (LPS). In adult male Sprague-Dawley rats maintained under propofol anesthesia (30 mg/kg/h), paralyzed with pancuronium (2 mg/kg/h) and mechanically ventilated (85-95 stroke/min, 2.5-3 ml/stroke), intravenous administration of LPS (15 or 30 mg/kg) induced an immediate hypotension, followed by a rebound increase and a secondary decrease in systemic arterial pressure (SAP). LPS also reduced the power density of the very low-frequency (0-0.25 Hz) and low-frequency (0.25-0.8 Hz) components of SAP signals (Phase ¢¹), which represented the sympathetic vasomotor tone, followed by an increase (Phase ¢º) and a secondary decrease (Phase ¢»). Pretreatment with microinjection of the selective non-peptide AT1 receptor antagonist, losartan (1.6 nmol), or the selective non-peptide AT2 receptor antagonist, PD-123319 (1.6 nmol), into the bilateral NRVL significantly reduced the survival time after the induction of acute experimental endotoxemia. Both pretreatments shortened the duration of Phase ¢º and Phase ¢» in acute endotoxemia, accelerated the secondary hypotension, and excited the power density of the very low-frequency. We conclude that endogenous angiotensin ¢º at the NRVL may play a crucial role in the maintenance of SAP during acute experimental endotoxemia, possibly via an action on both AT1 and AT2 subtype receptors on the very low-frequency component of SAP spectrum.