Journal of Neurophysiology, Vol 74, Issue 1 334-346, Copyright © 1995 by APS

ARTICLES

NMDA-induced burst discharge in guinea pig trigeminal motoneurons in vitro

Y. I. Kim and S. H. Chandler
Department of Physiological Science, University of California at Los Angeles 90024, USA.

1. The responses of guinea pig trigeminal motoneurons (TMNs) to N-methyl-D,L-aspartate (NMA) were studied using brain stem slice preparations and whole cell patch-clamp (n = 89) or conventional microelectrode (n = 22) recording techniques. The primary goals of this study were to determine whether N-methyl-D-aspartate (NMDA) receptor activation would produce spontaneous bursting activity in TMNs and, if so, the underlying mechanisms responsible for the generation of these bursts. 2. Bath-applied NMA (100-300 microM, n = 80) in standard perfusion medium elicited depolarization, increase in apparent input resistance (Rinp), and rhythmic burst discharges (1-90 s in duration) from TMNs. These effects were blocked by the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (AP5, 30 microM, n = 6), but not by the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 5-10 microM, n = 10). Furthermore, the burst-inducing effect of NMA was not mimicked by the non-NMDA receptor agonists kainate (KA, 5-10 microM, n = 6) and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA, 5-10 microM, n = 5). 3. In tetrodotoxin (TTX) treatment conditions (n = 13), NMA elicited depolarization, an increase in apparent Rinp, and rhythmic membrane potential oscillations without action potential bursts (i.e., plateau potentials), suggesting that the effects of NMA observed in the TTX-free condition resulted from activation of postsynaptic NMDA receptors. 4. Graded depolarization of neurons (n = 20) by intracellular direct current injection generally led to a graded increase in frequency and duration of the NMA-induced bursts and plateau potentials until these rhythmic events eventually became transformed into continuous spike discharge and maintained depolarization, respectively. Removal of Mg2+ from the perfusion medium (n = 11) also turned the bursts and plateau potentials into continuous spike discharge and maintained depolarization, respectively. 5. The effects of NMA on the current-voltage (I-V) curve after a depolarizing ramp voltage-clamp command (15-20 mV/s) were examined (n = 40). Under NMA (100-300 microM) conditions, the I-V relationship exhibited a region of negative slope conductance (NSC) between -60 and -35 mV, thus making the I-V relationship N-shaped. The NSC was abolished by AP5 (30 microM, n = 8), but not by CNQX (5-10 microM, n = 6). The I-V relationship in AMPA (3-10 microM, n = 5) or KA (3-10 microM, n = 5) was almost linear between -80 and -30 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				Y. Homma, R. D. Skinner, and E. Garcia-Rill Effects of Pedunculopontine Nucleus (PPN) Stimulation on Caudal Pontine Reticular Formation (PnC) Neurons In Vitro J Neurophysiol, June 1, 2002; 87(6): 3033 - 3047. [Abstract] [Full Text] [PDF]

				C.-F. Hsiao, N. Wu, M. S. Levine, and S. H. Chandler Development and Serotonergic Modulation of NMDA Bursting in Rat Trigeminal Motoneurons J Neurophysiol, March 1, 2002; 87(3): 1318 - 1328. [Abstract] [Full Text] [PDF]

				M.-J. Bourque and A. Kolta Properties and Interconnections of Trigeminal Interneurons of the Lateral Pontine Reticular Formation in the Rat J Neurophysiol, November 1, 2001; 86(5): 2583 - 2596. [Abstract] [Full Text] [PDF]

				N. Wu, C.-F. Hsiao, and S. H. Chandler Membrane Resonance and Subthreshold Membrane Oscillations in Mesencephalic V Neurons: Participants in Burst Generation J. Neurosci., June 1, 2001; 21(11): 3729 - 3739. [Abstract] [Full Text] [PDF]

				J. C. Rekling, G. D. Funk, D. A. Bayliss, X.-W. Dong, and J. L. Feldman Synaptic Control of Motoneuronal Excitability Physiol Rev, April 1, 2000; 80(2): 767 - 852. [Abstract] [Full Text] [PDF]

				C. A. del Negro, C.-F. Hsiao, and S. H. Chandler Outward Currents Influencing Bursting Dynamics in Guinea Pig Trigeminal Motoneurons J Neurophysiol, April 1, 1999; 81(4): 1478 - 1485. [Abstract] [Full Text] [PDF]

				C.-F. Hsiao, C. A. D. Negro, P. R. Trueblood, and S. H. Chandler Ionic Basis for Serotonin-Induced Bistable Membrane Properties in Guinea Pig Trigeminal Motoneurons J Neurophysiol, June 1, 1998; 79(6): 2847 - 2856. [Abstract] [Full Text] [PDF]

				S. Hochman and B. J. Schmidt Whole Cell Recordings of Lumbar Motoneurons During Locomotor-Like Activity in the In Vitro Neonatal Rat Spinal Cord J Neurophysiol, February 1, 1998; 79(2): 743 - 752. [Abstract] [Full Text] [PDF]

				A. Kolta In Vitro Investigation of Synaptic Relations Between Interneurons Surrounding the Trigeminal Motor Nucleus and Masseteric Motoneurons J Neurophysiol, September 1, 1997; 78(3): 1720 - 1725. [Abstract] [Full Text] [PDF]

				C. F. Hsiao, P. R. Trueblood, M. S. Levine, and S. H. Chandler Multiple Effects of Serotonin on Membrane Properties of Trigeminal Motoneurons In Vitro J Neurophysiol, June 1, 1997; 77(6): 2910 - 2924. [Abstract] [Full Text] [PDF]

				M. Kobayashi, T. Inoue, R. Matsuo, Y. Masuda, O. Hidaka, Y. Kang, and T. Morimoto Role of Calcium Conductances on Spike Afterpotentials in Rat Trigeminal Motoneurons J Neurophysiol, June 1, 1997; 77(6): 3273 - 3283. [Abstract] [Full Text] [PDF]

				M.-S. Rioult-Pedotti Intrinsic NMDA-Induced Oscillations in Motoneurons of an Adult Vertebrate Spinal Cord Are Masked by Inhibition J Neurophysiol, February 1, 1997; 77(2): 717 - 730. [Abstract] [Full Text] [PDF]