The variation in action of excitatory amino acids in relation to distance of iontophoretic application to spinal motoneurones.
Intracellular recordings were made from lumbosacral motoneurones of barbiturate-anaesthetized cats. DL-homocysteate (DLH) and L-glutamate were iontophoresed extracellularly over a range of distances from the impaled motoneurone. Movement of the iontophoretic electrode unit was controlled by a micromanipulator which was advanced independently of that moving the intracellular electrode. Depolarizations to DLH were first detected at a greater distance from the impaled motoneurones (mean, 383 micron) than depolarizations to L-glutamate (mean, 165 micron). As the point of application approached the soma of the motoneurone, depolarizations developed more rapidly, were larger and the latent period of the L-glutamate depolarization became shorter. Dendritic 'hot-spots' of the depolarizing action of L-glutamate were not detected.
Flatman
J A
JA
Lambert
J D
JD
Engberg
I
I
D000818:Animals; D002415:Cats; D005260:Female; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007478:Iontophoresis; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009474:Neurons / Q000187:drug effects*; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects*
D005971:Glutamates; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D006710:Homocysteine; C007956:homocysteic acid; D018698:Glutamic Acid