Electrical and chemical excitability appear one week before birth in the embryonic rat spinal cord.
Embryonic rat spinal cord cells were acutely dissociated with the enzyme papain, stained with a voltage-sensitive oxonol dye and incubated with various pharmacological agents. Changes in the fluorescence intensity and, by inference, membrane potential of the cells were analyzed in a flow cytometer. Veratridine caused depolarization of the cells in a TTX-sensitive manner from as early as embryonic day 13. Depolarizing responses to muscimol and kainate appeared slightly later, at embryonic days 14 and 15, and were blocked by the antagonists bicuculline and CNQX, respectively. Responses to veratridine and kainate did not occur in sodium-free medium. The emergence of these excitable membrane properties coincides with postmitotic differentiation and synaptic development in the embryonic spinal cord.
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
R N
RN
Mandler
A E
AE
Schaffner
E A
EA
Novotny
G D
GD
Lange
S V
SV
Smith
J L
JL
Barker
D000818:Animals; D004558:Electric Stimulation; D005260:Female; D005333:Fetus / Q000502:physiology; D005434:Flow Cytometry; D005453:Fluorescence; D007608:Kainic Acid / Q000494:pharmacology; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D009118:Muscimol / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000378:metabolism; D012542:Scattering, Radiation; D015222:Sodium Channels / Q000187:drug effects; D013116:Spinal Cord / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D013194:Staining and Labeling; D013268:Stimulation, Chemical; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D015222:Sodium Channels; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D014701:Veratridine; D007608:Kainic Acid