Glycine inhibition of glutamate evoked-release of norepinephrine in the hypothalamus is strychnine-insensitive

The effects of glycine (GLY), d-serine (d-SER), kynurenic acid (KYN), and 7-Cl kynurenic acid (7-Cl KYN), on the evoked release of endogenous norepinephrine (NE) by l-glutamate (l-GLU) in rat hypothalamic slices was investigated. KYN (500 and 100 μM) and 7-Cl KYN (10 μM) blocked evoked release of NE by l-GLU (1 mM). The inhibitory effects of 100 μM KYN on evoked release of NE by l-GLU were reversed by 10 μM and 100 μM d-SER and, but not 10 or 100 μM GLY. When KYN was not present in the superfusate, superfusion with either 10 or 100 μM GLY alone simultaneously with 1 mM l-GLU blocked the evoked release of NE produced by l-GLU. The addition of strychnine (3 or 100 μM) to the superfusate did not block the inhibitory effects of 10 μM GLY on l-GLU-evoked NE release. These findings suggest that a novel strychnine-resistant GLY receptor is present in the rat hypothalamus.