Intracellular activity of rat spinal cord motoneurons in slices.
Using a modification of Aghajanian and Rasmussen's techniques, we have developed an adult rat cervical spinal cord slice preparation in which motoneurons remain viable. Key factors are replacement of all sodium ions in the perfusion medium with sucrose during cutting and incubation, and gentle manipulation of the tissues to prevent root damage during removal. Intracellular recordings were confirmed as motoneuronal by intracellular injection of Lucifer yellow, allowing visualization of dendrites and cell body, and showing an axonal bleb at the cut end in the ventral root. Over 50 neurons were recorded for periods of between 30 min and 4 h. Cervical motoneurons (n=10) had an average membrane potential of -62 mV, average input resistance of 24 M(Omega), and showed no spontaneous activity. Ionophoresis application of the glutamate agonists, AMPA and NMDA, revealed potent excitation by AMPA but little or no response to NMDA. While NMDA receptors reportedly are prominent in developing rodent motoneurons, these observations indicate otherwise in the adult. Upon prolonged ionophoresis, or bath application, depolarizing responses to AMPA led to depolarization and spike inactivation that was often irreversible. The apparent lack of desensitization of AMPA responses, usually seen in other neurons, may underlie the unique vulnerability of motoneurons to excitotoxic damage.
Hori
N
N
School of Public Health, University at Albany, One University Place, Rm. B242, Rensselaer, NY 12144-3456, USA.
Tan
Y
Y
Strominger
N L
NL
Carpenter
D O
DO
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005456:Fluorescent Dyes; D007546:Isoquinolines; D008297:Male; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009482:Neurophysiology / Q000295:instrumentation / Q000379:methods*; D009924:Organ Culture Techniques / Q000295:instrumentation / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D005456:Fluorescent Dyes; D007546:Isoquinolines; D017470:Receptors, Glutamate; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C017475:lucifer yellow