Vestibular nucleus N-methyl-D-aspartate receptors contribute to spontaneous nystagmus generation following unilateral labyrinthectomy in guinea pigs.
We investigated the effects of a non-competitive N-methyl-D-aspartate (NMDA) receptor/channel antagonist ((+)MK-801)) or an L-type Ca(2+) channel antagonist (nifedipine), delivered into the ipsilateral vestibular nucleus complex (VNC) before a unilateral labyrinthectomy (UL), on spontaneous nystagmus (SN) generation. Guinea pigs received either (+)MK-801 (5 or 12.5 microg); the less active enantiomer, (-)MK-801 (5 or 12.5 microg); nifedipine (5 or 10 microg); or vehicle, via cannula in the ipsilateral VNC. (+)MK-801, but not nifedipine, significantly decreased mean SN frequencies at 6 h post-UL, compared to controls (P<0.02) and reduced the rate of SN compensation (P<0.05). These results suggest that the SN expression is partly induced by NMDA receptor activation in the ipsilateral VNC at the time of the UL.
Sansom
A J
AJ
Department of Pharmacology, School of Medical Sciences, University of Otago Medical School, University of Otago, Dunedin, New Zealand.
Smith
P F
PF
Darlington
C L
CL
Laverty
R
R
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D007758:Ear, Inner / Q000502:physiology*; D007839:Functional Laterality; D006168:Guinea Pigs; D009543:Nifedipine / Q000494:pharmacology; D009760:Nystagmus, Physiologic / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D013237:Stereoisomerism; D014722:Vestibule, Labyrinth / Q000502:physiology*
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D009543:Nifedipine