Characteristics of substance P-evoked release of amino acids from neonatal rat spinal cord.
The characteristics of release of amino acids evoked by substance P from the neonatal rat spinal cord were examined. A hemisected spinal cord was continuously perfused and the release of amino acids into the perfusate was measured using high-performance liquid chromatography with a precolumn derivatization technique. Substance P (10 microM) evoked a significant increase in the release of aspartate, glutamate, GABA, glycine and taurine. The substance P-evoked release of these five amino acids was not reduced by Ca(2+)-free medium, but was blocked by [D-Pro4,D-Trp] substance P4-11 (10 microM). Perfusion of the spinal cord with low-Na+ medium (22 mM) induced a marked increase in the high-K+ (90mM)-evoked release of GABA, glutamate and glycine. In contrast, the substance P-evoked release of the five amino acids was significantly decreased by the low-Na+ medium. Similarly, perfusion of the spinal cord with low-Cl- medium (8 mM) increased the high-K(+)-evoked release of GABA and glycine, but decreased the substance P-evoked release of GABA, glycine and taurine. The substance P-evoked release of the five amino acids was dose-dependently blocked by d-tubocurarine (3-10 microM), whereas it was not blocked by tetrodotoxin (0.2 microM) or amiloride (30 microM). Compound 48/80 (10 micrograms/ml), a histamine-releasing agent on mast cells, evoked release of the amino acids from the spinal cord with characteristics similar to those of substance P-evoked amino acid release.(ABSTRACT TRUNCATED AT 250 WORDS)
D000584:Amiloride / Q000494:pharmacology; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D066298:In Vitro Techniques; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D013373:Substance P / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015320:Tachykinins / Q000037:antagonists & inhibitors; D013779:Tetrodotoxin / Q000494:pharmacology; D014403:Tubocurarine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D000596:Amino Acids; D002712:Chlorides; D003473:Neuromuscular Nondepolarizing Agents; D015320:Tachykinins; D013373:Substance P; D003189:p-Methoxy-N-methylphenethylamine; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D000584:Amiloride; C045800:substance P, Phe(5)-Trp(7,9)-Leu(11)-; D012964:Sodium; D011188:Potassium; D014403:Tubocurarine