Effect of a high-salt diet on gamma-aminobutyric acid-mediated responses in the nucleus tractus solitarius of Sprague-Dawley rats.
Previous study using an indirect gamma-aminobutyric acid (GABA) agonist indicated that high salt intake enhances sensitivity of nucleus tractus solitarius (NTS) projecting inhibitory input to rostral ventrolateral medulla sympathoexcitatory neurons. We further investigated the relationship between salt intake and the GABA system in NTS. Sprague-Dawley (S-D) rats consuming high dietary salt (8%) or low dietary salt (0.3%) for 3 weeks were used. Under chloralose-anesthesia, baseline arterial pressure (AP) and heart rate (HR) were similar in both groups. Bilateral injection into NTS of nipecotic acid, GABA(A) receptor agonist (muscimol), or GABA(B) receptor agonist (baclofen) elicited greater pressor responses in high-salt group. GABA(A) receptor antagonist, bicuculline and GABA(B) receptor antagonist, CGP-35348 elicited greater depressor responses. Phenylephrine or nitroprusside (i.v.) elicited similar respective increases or decreases in AP in both groups. Baroreflex sensitivity was similar. Thus, high-salt intake enhances both GABA(A) receptor- and GABA(B) receptor-mediated responses within NTS, thereby inhibiting elevation of AP.
Second Department of Internal Medicine, Nihon University School of Medicine, 30-1, Oyaguchi-Kamichou, Itabashi-ku, Tokyo 173-8610, Japan.
Yuichi
Y
Masubuchi
Kazuyoshi
K
Tsukamoto
Osamu
O
Isogai
Yoshiharu
Y
Yajima
Satoru
S
Ito
Satoshi
S
Saito
Takahisa
T
Uchiyama
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001640:Bicuculline / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005526:Food, Formulated; D018755:GABA Agonists / Q000494:pharmacology; D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009557:Nipecotic Acids / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects* / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018755:GABA Agonists; D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D009557:Nipecotic Acids; D009943:Organophosphorus Compounds; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D017673:Sodium Chloride, Dietary; D009599:Nitroprusside; C030278:nipecotic acid; D010656:Phenylephrine; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C066430:CGP 35348; D001418:Baclofen; D001640:Bicuculline