Evidence for neuronal release of isotopically labelled glycine from the rat ventral medullary surface in vivo.
Spontaneous and stimulus-induced release of isotopically labelled glycine was studied in the superfused rat dorsal or ventral medullary surface in vivo. Superfusion of the ventral medullary surface of anesthetized (urethane, 1.2 g/kg, ip) male adult Wistar rats (250-350 g) with high K+ (40 mM) surrogate cerebrospinal fluid (CSF) produced an average increase of 45% over the spontaneous efflux of exogeneously applied glycine (N = 5, P < 0.01). In experiments in which the calcium of the CSF was replaced by an equimolar amount of magnesium, the increase in glycine efflux in response to high K+ was reduced to 15%, a value not statistically different from that observed in control experiments (N = 6). Veratridine stimulation evoked a large (80%) increase in glycine efflux (N = 5, P < 0.001), which was inhibited by tetrodotoxin. High potassium or veratridine failed to modify spontaneous release of glycine on the dorsal medullary surface. Results obtained in control experiments showed that neither high K+ nor veratridine is effective in modifying spontaneous efflux of [3H]-leucine or [3H]-inulin on the ventral or dorsal medullary surface. These data support the hypothesis that glycine is a neurotransmitter on the ventral medullary surface and that it may be part of neural pathways involved in cardiorespiratory regulation present in this region.
de-Oliveira
C V
CV
Departamento de Fisiologia, Universidade Federal de São Paulo, Brasil.
Assumpção
J A
JA
Confessor
Y Q
YQ
Guertzenstein
P G
PG
Cravo
S L
SL
D000818:Animals; D005998:Glycine / Q000378:metabolism*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011868:Radioisotopes; D051381:Rats; D017208:Rats, Wistar; D014701:Veratridine / Q000494:pharmacology
D011868:Radioisotopes; D014701:Veratridine; D011188:Potassium; D005998:Glycine