Nitric oxide actions in paraventricular nucleus: cardiovascular and neurochemical implications.
We have examined potential functions of nitric oxide (NO) within the paraventricular nucleus (PVN) in urethan-anesthetized male Sprague-Dawley rats. Initial experiments demonstrated microinjection of 50 pmol of the NO donor, sodium nitroprusside (SNP), directly into the PVN resulted in significant decreases in mean blood pressure (BP) (-3,312 +/- 1,189 mmHg/s over 300-s response time; P < 0.05). To determine whether such effects were attributable to SNP-induced NO release, NO was administered into PVN directly by bilateral microdialysis of NO-containing artificial cerebrospinal fluid (NO-aCSF), a process that results in delivery of approximately 50 pmol NO.PVN-1 x min-1. Such microdialysis resulted in significant decreases in BP (-5,121 +/- 817 mmHg/s over 1,200-s response time; P < 0.005), while aCSF microdialysis was without effect (1,298 +/- 1,071 mmHg/s over 1,200-s response time; P > 0.1). Amino acid concentrations were measured in dialysates collected during perfusion of the same PVN sites with either aCSF or NO-aCSF by high-performance liquid chromatography (HPLC) analysis. NO-aCSF induced significant increases in aspartate (aCSF 31 +/- 7 pmol/30 min; NO-aCSF 134 +/- 33 pmol/30 min; P < 0.05), glutamate (aCSF 36 +/- 5 pmol/30 min; NO-aCSF 417 +/- 108 pmol/30 min; P < 0.02), gamma-aminobutyric acid (aCSF 4.1 +/- 0.7 pmol/30 min; NO-aCSF 104 +/- 29 pmol/30 min; P < 0.02), and taurine (aCSF 34 +/- 3 pmol/30 min; NO-aCSF 117 +/- 24 pmol/30 min; P < 0.01) concentrations, while alanine, glutamine, and serine concentrations were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Horn
T
T
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Smith
P M
PM
McLaughlin
B E
BE
Bauce
L
L
Marks
G S
GS
Pittman
Q J
QJ
Ferguson
A V
AV
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002319:Cardiovascular System / Q000187:drug effects*; D008297:Male; D017551:Microdialysis; D008845:Microinjections; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D009599:Nitroprusside / Q000008:administration & dosage / Q000494:pharmacology; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012996:Solutions
D000596:Amino Acids; D012996:Solutions; D009599:Nitroprusside; D009569:Nitric Oxide