Evidence for neuronal release of isotopically labelled glycine from the rat ventral medullary surface in vivo

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deOliveira, CVR
Assumpção, Jurandyr D'Avila [UNIFESP]
Confessor, Yara Queiroga [UNIFESP]
Guertzenstein, Pedro Gaspar [UNIFESP]
Cravo, Sergio Luiz [UNIFESP]
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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 exogenously 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 [H-3]-leucine or [H-3]-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.
Brazilian Journal Of Medical And Biological Research. Sao Paulo: Assoc Bras Divulg Cientifica, v. 29, n. 4, p. 527-532, 1996.