Glycine release from hippocampal slices in developing and ageing mice: modulation by glutamatergic receptors

The release of preloaded [3H]glycine from hippocampal slices in developing and ageing mice (from 7 days to 22 months) was characterized using a superfusion system. The release was Ca(2+)-independent in each age group studied. The basal release and the responses to potassium stimulation were fairly constant during the whole life span. The release was potentiated by the glutamate receptor agonists kainate, N-methyl-D-aspartate (NMDA), tetrazolylglycine, quisqualate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) in developing mice, but only kainate was effective in adult and aged animals. The kainate effect was not modified by the antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in adult and old mice, indicating that glutamatergic systems may not be involved in the release. On the other hand, hippocampal glycine release in immature mice seems to be subject to regulation by both NMDA and non-NMDA (kainate and AMPA) receptors. The potentiations by NMDA and AMPA were antagonized by dizocilpine (MK-801) and CNQX, respectively. The modulation of glycine release by glutamatergic receptors could be of importance in the regulation of synaptic glycine levels in the developing hippocampus.