Central Sodium Loading Modifies Norepinephrine Content in the Ventrolateral Medulla and Blood Pressure in Rats

Abstract

We evaluated the effects of intracerebroventricular (ICV) infusion of hypertonic NaC1 on blood pressure (BP) control as well as on NE content in the ventrolateral medulla (VLM). Nine groups of Wistar rats received 10 day's ICV infusion of NaC1 solutions containing either norepinephrine (NE, 1.3 μg/min) or a synthetic NE precursor, 1-threo-3,4-dihydroxyphenylserine (1-DOPS, 17 μ g/min) for 3 concentrations (0.15M, 0.8M or 1.5M) of NaC1. On day 9, only the group on ICV infusion of 1.5M NaC1 alone had a significant rise in BP (133 ± 3 mmHg, P < 0.05 vs control) while other groups remained normotensive. The ICV infusion of 1.5M NaC1 reduced NE content, determined by a microdialysis method, in the VLM while the concomitant ICV infusion of NE or 1-DOPS restored it suggesting that the decrease in NE content in the VLM may be a contributing factor in the BP elevation by the central salt loading.

Key Words:

• Ventrolateral medulla
• Norepinephrine
• L-DOPS Microdialysis
• Blood pressure