Specific Glycine Uptake by Identified Neurons

Glycine is taken up twice as rapidly by neurons R3-R14 as by other identified neurons in the Aplysia parietovisceral ganglion. Earlier studies had shown that R3R14 have much higher glycine concentrations than other Aplysia neurons. Most of the glycine taken up by R3-R14 was biochemically untransformed for at least 1 h following its uptake. Glycine is actively transported into R3-R14 and other Aplysia neurons by carrier-mediated processes. Glycine uptake by R3-R14 was markedly reduced in the absence of Na + and in the presence of Hg 2+, while these treatments had little effect on glycine uptake by other Aplysia neurons. There appears to be a special glycine uptake system present in R3-R14 and a general glycine uptake system common to all Aplysia neurons. The elevated glycine concentrations and special glycine uptake associated with R3-R14 may indicate that glycine is utilized as a neurotransmitter by those neurons.