Open AccessInhibition of glial glutamate transporter GLT 1 in the nucleus of the solitary tract attenuates baroreflex control of sympathetic nerve activity and heart rate
Author(s) -
Yamamoto Kenta,
Mifflin Steve
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13877
Subject(s) - baroreflex , glutamate receptor , phenylephrine , solitary tract , medicine , rostral ventrolateral medulla , ionotropic effect , solitary nucleus , endocrinology , brainstem , anesthesia , pharmacology , heart rate , receptor , blood pressure
The astrocytic glutamate transporter ( GLT 1) plays an important role in the maintenance of extracellular glutamate concentration below neurotoxic levels in brain. However, the functional role of GLT 1 within the nucleus of the solitary tract ( NTS ) in the regulation of cardiovascular function remains unclear. We examined the effect of inhibiting GLT 1 in the subpostremal NTS on mean arterial pressure ( MAP ), renal sympathetic nerve activity ( RSNA ) and heart rate ( HR ) in anesthetized, artificially ventilated rats. It was found that dihydrokainate ( DHK ; inhibitor of GLT 1, 5 mmol/L , 100 nL) injections into the NTS ( n = 6) decreased MAP (50 ± 10 mmHg, mean ± SD ), RSNA (89 ± 14%) and HR (37 ± 6 bpm). Pretreatment with kynurenate ( KYN ; glutamate receptor antagonist, 5 mmol/L, 30 μ L) topically applied to the dorsal surface of the brainstem ( n = 4) attenuated the responses to NTS injections of DHK ( P < 0.01). The effect of DHK on arterial baroreflex function was examined using i.v. infusions of phenylephrine and nitroprusside. DHK reduced baroreflex response range (maximum−minimum) of RSNA by 91 ± 2% and HR by 83 ± 5% ( n = 6, P < 0.001). These results indicate that inhibition of GLT 1 within the NTS decreases MAP , RSNA , and HR by the activation of ionotropic glutamate receptors. As a result, baroreflex control of RSNA and HR was dramatically attenuated. The astrocytic glutamate transporter in the NTS plays an important role in the maintenance and regulation of cardiovascular function.