The synaptic activation of N-methyl-D-aspartate receptors in the rat medial vestibular nucleus.
1. We examined the synaptic activation of N-methyl-D-aspartate (NMDA) receptors by stimulation of primary vestibular afferent projections to second-order neurons in the medial vestibular nucleus (MVN) using whole cell patch-clamp recording methods in rat brain stem slices maintained in vitro. 2. Stimulation of the vestibular nerve (nVIII) evoked monosynaptic excitatory postsynaptic potentials (EPSPs) in second-order MVN neurons. Bath application of the gamma-aminobutyric acid receptor antagonist bicuculline (10 microM) revealed a late, slow EPSP that was blocked by the NMDA receptor antagonist D-2-amino-5-phosphonovalerate (D-AP5; 50 microM) and displayed a voltage-dependent reduction at hyperpolarized potentials in the presence of external magnesium (1 mM). The early component of the nVIII-evoked EPSP in the presence of bicuculline was blocked by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX; 10 microM) and displayed linear current-voltage relations in the presence of external magnesium. 3. In some cells both components of the EPSP were blocked by DNQX, whereas only the late component was sensitive to D-AP5, indicating that NMDA receptors also mediate excitation via intrinsic pathways within MVN. 4. The NMDA receptor-mediated excitatory postsynaptic current (EPSC) evoked by nVIII stimulation was recorded in voltage-clamped MVN neurons in a magnesium-free saline containing bicuculline (10 microM) and DNQX (10 microM). At -80 mV the NMDA receptor-mediated EPSC (latency = 2.7 ms) displayed a slow rise time (10-90%, 5.8 ms) and exhibited a biexponential decay [time constant of fast component of decay (tau s) = 27.6 ms, time constant of slow component of decay (tau s) = 147.4 ms].(ABSTRACT TRUNCATED AT 250 WORDS)
Kinney
G A
GA
Department of Physiology, Northwestern University Medical School, Chicago, Illinois 60611.
Peterson
B W
BW
Slater
N T
NT
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D005260:Female; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D014726:Vestibular Nuclei / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate