Signaling pathway of glutamate in the vestibular nuclei following acute hypotension in rats.
Acute hypotension induces excitation of electrical activity and expression of c-Fos protein and phosphorylated extracellular signal-regulated kinase (pERK) in the vestibular nuclei. Expression of c-Fos protein and pERK is mediated by the excitatory neurotransmitter, glutamate. In this study, in order to investigate the signaling pathway of glutamate in the vestibular nuclei following acute hypotension, expression of the NR2B subunit of glutamate N-methyl-D-aspartate (NMDA) receptors and the GluR1 subunit of glutamate alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors was measured by Western blotting in the medial vestibular nucleus (MVN) following acute hypotension in bilateral labyrinthectomized (BL) rats. In intact labyrinthine animals, acute hypotension increased expression of pGluR1 and pNR2B in the MVN. Expression of pGluR1 Ser831 and Ser845 peaked at 5 and 30 min after acute hypotension and expression of pNR2B peaked at 60 min after acute hypotension, respectively. In BL animals, expression of pGluR1 Ser831, pGluR1 Ser845, and pNR2B was decreased significantly compared to intact labyrinthine animals following acute hypotension. These results suggest that excitatory afferent signals from the peripheral vestibular receptors, resulting from acute hypotension, release glutamate into postsynaptic neurons in the vestibular nuclei and the excitatory signals are transmitted through the GluR1 subunit of the AMPA receptors and the NR2B subunits of the NMDA receptors in the vestibular system.
Choi
Myoung Ae
MA
Department of Physiology, Wonkwang University College of Medicine, and VestibuloCochlear Research Center at Wonkwang University, Iksan 570-749, South Korea.
Lee
Jae Hee
JH
Hwang
Ji Hyo
JH
Choi
Suck Jun
SJ
Kim
Min Sun
MS
Park
Byung Rim
BR
D000818:Animals; D001147:Arsanilic Acid / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D007022:Hypotension / Q000209:etiology / Q000473:pathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014726:Vestibular Nuclei / Q000187:drug effects / Q000378:metabolism*; D014722:Vestibule, Labyrinth / Q000601:surgery
D001147:Arsanilic Acid; D018698:Glutamic Acid; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D012694:Serine; C121001:NR2B NMDA receptor