Primary afferent depolarization and changes in extracellular potassium concentration induced by L-glutamate and L-proline in the isolated spinal cord of the frog.
To test the hypothesis that L-proline acts as an antagonist on glutamate receptors [17, 18], the interaction between L-glutamate and L-proline was studied in the isolated spinal cord of the frog. Glutamate at concentrations of 10(-6) -5 x 10(-3) mol/l depolarized the primary afferent fibres and increased extracellular potassium concentration, [K+]e, by 0.3-4 mmol/l. Repeated applications lead to inactivation of the response. L-Proline at 5 x 10(-3) -10(-2) mol/l, also depolarized the primary afferents and increased [K+]e by 0.5-2 mmol/l, but there was only a slight decrease of the effects after repeated application. The effects were additive when the amino acids were applied simultaneously. The effect of L-proline was still present when it was applied during inactivation of the glutamate receptors. This suggests that L-glutamate and L-proline act on different receptors.
D000344:Afferent Pathways / Q000187:drug effects; D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects*; D005727:Ganglia, Spinal / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D011188:Potassium / Q000378:metabolism*; D011392:Proline / Q000494:pharmacology*; D011896:Rana temporaria; D011956:Receptors, Cell Surface / Q000187:drug effects; D017470:Receptors, Glutamate; D013116:Spinal Cord / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D005971:Glutamates; D011956:Receptors, Cell Surface; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D011392:Proline; D011188:Potassium