Uneven distribution of excitatory amino acid receptors on ventral horn neurones of newborn rat spinal cord.

Abstract

SUMMARY1. The distribution of excitatory amino acid receptors on ventral horn neurones was investigated using slices of newborn rat spinal cord.2. The neurone and the tip of the pipette used to inject amino acids were visualized using Lucifer Yellow under a fluorescent microscope. The pipette was precisely located on the soma and dendrite of the neurone under visual control, and L-glutamate (Glu), L-aspartate (Asp), N-methyl-D-aspartate (NMDA), kainate (KA) and quisqualate (Quis) were ionophoretically applied with a short pulse. The potential changes were intracellularly recorded from the soma.3. Sensitivity to Glu as tested with short pulses (1-2 ms) was almost the same at the soma and along dendrites. 4. The amplitude of the responses to NMDA produced at the soma and the proximal part of the dendrite was about the same as that of Glu, but smaller than that of Glu at the distal part of the dendrite. Suppression of the Glu potential by an NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV), was greater at the soma than at the dendrite, suggesting that the contribution of NMDA receptors to the Glu potential was greater at the soma.5. Sensitivity to Asp was about one-half that to Glu sensitivity on the soma and even less on the dendrite. Sensitivity to KA was high at the soma and low at the dendrite. However, Quis responses were produced throughout the neurone.6. The Quis response induced by the application of a short pulse showed two phases: a fast response followed by a very slow depolarization that lasted more than 10 s.7. The fast Quis response was easily desensitized and insensitive to APV. The time course of the fast Quis potential was shorter than that of Glu.8. The slow Quis response was more pronounced at the dendrites than at the soma and was reduced by the intracellular irnjection of EGTA, suggesting the contribution of Ca2+ in the cell, possibly mediated by a second messenger system. 9. Experimental results suggest that the distribution of excitatory amino acid receptors differs between the soma and the dendrites of spinal neurones. 9PHY 439

NMDA and AMPA receptors on neocortical neurons are differentially distributed

“…Also, in spinal neurons recorded in vivo and in vitro , glutamate applications to dendritic sites proved to be more effective than to the soma. (Zieglgänsberger & Champagnat 1979;Onodera & Takeuchi 1991).…”

Synaptic Mechanism for the Sustained Activation of Oculomotor Integrator Circuits in the Rat Prepositus Hypoglossi Nucleus: Contribution of Ca2+-Permeable AMPA Receptors

“…The NMDA/AMPA ratio was positively correlated with RI (r ϭ 0.51; p Ͻ 0.01), although some neurons exhibiting RI Ͻ 1 had high NMDA/AMPA ratios. Previous studies on cerebral and hippocampal pyramidal neurons and spinal cord neurons have shown that the expression of NMDA receptors is constant or decreases from the soma to the dendrites, but the expression of AMPA receptors in the soma is lower than in the dendrites (Onodera and Takeuchi, 1991;Dodt et al, 1998;Andrasfalvy and Magee, 2001). If the distribution of AMPA and NMDA receptors at the somatic-dendritic membrane in PHN neurons is similar to that in pyramidal and spinal neurons, the NMDA/AMPA ratio measured at the soma of PHN neurons may actually be smaller at synaptic sites presumably located at the dendrites.…”

Participation of NMDA and non‐NMDA excitatory amino acid receptors in the mediation of spinal reflex potentials in rats: an in vivo study

“…: <10 ms; Mayer et al, 1991) and complete recovery from desensitization after short pulse ejection of glutamate onto motoneurones, comparable to the synaptic release, takes more than 1 s. (Onodera & Takeuchi, 1991). On the other hand, the onset (Onodera & Takeuchi, 1991) and the desensitization kinetics of NMDA receptors is slower and lesser in degree (time const. : t 300ms, Mayer et al, 1991).…”