L-proline depolarizes rat spinal motoneurones by an excitatory amino acid antagonist-sensitive mechanism.
1 Isolated spinal cords prepared from neonatal rats were used to examine the effects of L-proline (L-Pro). 2 L-Pro (1-8 mM) depolarized ventral and dorsal roots in a dose-dependent manner with one sixth of the potency of L-glutamate (L-Glu). L-Pro was four times more potent than D-Pro. Prolonged application of L-Pro produced a plateau depolarization of motoneurones with no apparent fade. 3 Omission of calcium ions from the medium potentiated the depolarizing actions of L-Pro, L-Glu and quisqualate. 4 L-Pro was antagonized by concentrations of 2-amino-5-phosphonovalerate (25 microM), gamma-D-glutamylglycine (100 microM) and Mg2+ ions (1 mM) that depressed responses to N-methyl-D-aspartate (NMDA). The NMDA receptor-mediated component of the response to L-Pro was estimated to be 60-70%. 5 These data suggest that L-Pro should be considered as a possible excitatory neurotransmitter and that, because L-Pro is a neutral compound, excitatory amino receptors may not require an agonist to possess two anionic groups and one cationic group.
Ault
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B
Department of Pharmacology, Burroughs Wellcome Co., Research Triangle Park, North Carolina 27709.
Wang
C M
CM
Yawn
B C
BC
D000596:Amino Acids / Q000037:antagonists & inhibitors*; D000818:Animals; D002118:Calcium / Q000502:physiology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D009046:Motor Neurons / Q000187:drug effects*; D011392:Proline / Q000494:pharmacology*; D051381:Rats; D013116:Spinal Cord / Q000166:cytology; D013779:Tetrodotoxin / Q000494:pharmacology
D000596:Amino Acids; D013779:Tetrodotoxin; D011392:Proline; D008274:Magnesium; D002118:Calcium