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 per cent 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 per cent, a value not statistically different from that observed in control experiments (N = 6). Veratridine stimulation evoked a large (80 per cent) 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 [(3)H]-leucine or [(3)H]-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.

Efluxo de amino-acidos inibidores no cortex cerebelar do rato. / Amins acids inhibitor efflux in cerebellar cortex of the rat

Estudou-se a liberacao in vivo de GABA, taurina e glicina radiativos, induzida por diferentes agentes despolarizadores aplicados diretamente ao cortex cerebelar exposto de ratos antestesiados. Os resultados obtidos indicam que a glicina provavelmente nao e neurotransmissora no cortex cerebelar, enquanto que o GABA e a taurina devem estar envolvidos na transmissao sinaptica naquela estrutura, como neurotransmissores e talvez, tambem, como moduladores da excitabilidade neuronal

Efluxo de provaveis amino-acidos neurotransmissores inibidores da regiao do nucleo cuneiforme do rato. / Efflux of the inhibitory transmitter probable amino acids of the cuneiform nucleus region of the rat

GABA, taurina e glicina isotopicamente marcdos, em preparacoes in vivo, induzida marcados, em preparacoes in vitro induzida por diferentes agentes despolarizadores aplicados diretamente sobre a superficie pial da regiao dorsal da medula (MD). Os resultados obtidos permitem concluir que o GABA e, provavelmente, o principal neurotransmissor inibidor nessa regiao, a taurina provavelmente esta envolvida como moduladora da excitabilidade neuronal, enquanto que a glicina nao deve ter acao neurotransmissora da MD