GLYCINE RELEASE FROM HIPPOCAMPAL SLICES IN DEVELOPING AND AGING MICE - MODULATION BY GLUTAMATERGIC RECEPTORS

The release of preloaded [H-3]glycine from hippocampal slices in devel oping and ageing mice (from 7 days to 22 months) was characterized usi ng a superfusion system. The release was Ca2+-independent in each age group studied. The basal release and the responses to potassium stimul ation were fairly constant during the whole life span. The release was potentiated by the glutamate receptor agonists kainate, N-methyl-D-as partate (NMDA), tetrazolylglycine, quisqualate and pha-amino-3-hydroxy -5-methyl-4-isoxazolepropionate (AMPA) in developing mice, but only ka inate was effective in adult and aged animals. The kainate effect was not modified by the antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (C NQX) 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 NM DA and non-NMDA (kainate and AMPA) receptors. The potentiations by NMD A and AMPA were antagonized by dizocilpine (MK-801) and CNQX, respecti vely. The modulation of glycine release by glutamatergic receptors cou ld be of importance in the regulation of synaptic glycine levels in th e developing hippocampus.