High NaCl diet enhances arterial baroreceptor reflex in NaCl-sensitive spontaneously hypertensive rats.
Previous studies from our laboratory have shown that arterial baroreceptor reflex control of lumbar sympathetic nerve activity is blunted in the NaCl-sensitive spontaneously hypertensive rat (SHR-S) compared with either the NaCl-resistant spontaneously hypertensive rat (SHR-R) or the normotensive Wistar-Kyoto (WKY) rat. In the current study, the effect of dietary NaCl supplementation on arterial baroreceptor reflex control of lumbar sympathetic nerve activity and heart rate was assessed in SHR-S and control SHR-R and WKY rats. Male SHR-S, SHR-R, and WKY rats were fed diets containing either 1% or 8% NaCl beginning at 7 weeks of age and were studied at age 9-10 weeks. Arterial baroreceptor reflex-mediated changes in lumbar sympathetic nerve activity and heart rate were recorded in conscious, unrestrained rats during phenylephrine-induced (15-40 micrograms/kg/min) and nitroprusside-induced (15-300 micrograms/kg/min) changes in mean arterial pressure. SHR-S maintained on a 1% NaCl diet had blunted baroreceptor reflex control of lumbar sympathetic nerve activity during acute increases in MAP compared with SHR-R and WKY rats (p less than 0.05). After ingestion of the 8% NaCl diet, this blunting was absent, indicating enhancement of baroreceptor reflex control of lumbar sympathetic nerve activity. SHR-S maintained on a 1% NaCl diet also had blunted arterial baroreceptor control of lumbar sympathetic nerve activity during nitroprusside-induced decreases in mean arterial pressure compared with WKY rats, but this was not significantly altered during ingestion of the 8% NaCl diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Calhoun
D A
DA
Department of Medicine, University of Alabama, Birmingham 35294.
Wyss
J M
JM
Oparil
S
S
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004032:Diet; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012018:Reflex / Q000187:drug effects*; D012965:Sodium Chloride / Q000494:pharmacology*; D013564:Sympathetic Nervous System / Q000502:physiology
D010656:Phenylephrine; D012965:Sodium Chloride