Properties of NMDA receptors in rat spinal cord motoneurons.
Postnatal development and properties of N-methyl-d-aspartate (NMDA) receptors were studied with whole-cell and outside-out patch-clamp techniques in interneurons and fluorescence-labelled motoneurons in rat spinal cord slices. Both the absolute amplitude of NMDA-induced currents and currents normalized with respect to the motoneuron capacitance increased significantly at postnatal days 10-13 when compared to the responses evoked at postnatal days 2-3. The mean amplitude of the responses to kainate also increased in motoneurons of postnatal days 10-13. Single-channel currents induced by low concentrations of glutamate, exhibited four distinct amplitude levels corresponding to 19.2 +/- 2.4 pS, 38.4 +/- 3.5 pS, 56.3 +/- 2. 4 pS and 69.6 +/- 3.7 pS. In contrast, the conductance of single channels, recorded under identical conditions, in rat spinal cord interneurons was less, 15.3 +/- 3.2 pS, 29.9 +/- 5.4 pS, 46.7 +/- 4. 8 pS and 62.4 +/- 3.9 pS. The high (56/70 pS) conductance single-channel openings in motoneuron patches were sensitive to NMDA receptor inhibitors D-2-amino-5-phosphonovalerate, 7-chlorokynurenic acid and ifenprodil. Whole-cell NMDA-evoked currents were blocked in a voltage-dependent manner by extracellular Mg2+ with an apparent dissociation constant for Mg2+ binding at 0 mV of 1.8 +/- 0.5 mm. The conductance and relative distribution of NMDA receptor channel openings induced by 1 micrometer glutamate in patches isolated from the motoneurons were independent of age from postnatal day 4 to 14. The results suggest that the properties of NMDA receptor channels in motoneurons differ from those in spinal cord interneurons and cells transfected with NR1/NR2 subunits.
Palecek
J I
JI
Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 142 20 Prague 4, Czech Republic.
Abdrachmanova
G
G
Vlachová
V
V
Vyklick
L
L
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D004553:Electric Conductivity; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007608:Kainic Acid / Q000494:pharmacology; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009046:Motor Neurons / Q000737:chemistry* / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D013116:Spinal Cord / Q000737:chemistry* / Q000166:cytology*
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D010880:Piperidines; D016194:Receptors, N-Methyl-D-Aspartate; C084485:7-chlorothiokynurenic acid; D018698:Glutamic Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; D008274:Magnesium; C010739:ifenprodil; D007608:Kainic Acid; D005998:Glycine