Glycine is an inhibitory neurotransmitter in thecentral nervous system, especially in thespinal cord, brainstem, and retina. Whenglycine receptors are activated, chlorideenters the neuron via ionotropic receptors, causing an Inhibitory postsynaptic potential(IPSP). Strychnine is a strong antagonist at ionotropic glycine receptors, whereasbicuculline is a weak one. Glycine is a required co-agonist along with glutamate forNMDA receptors. In contrast to the inhibitory role of glycine in the spinal cord, this behaviour is facilitated at the (NMDA)glutamatergic receptors which are excitatory.[20] The LD50 of glycine is 7930 mg/kg in rats (oral),[21] and it usually causes death by hyperexcitability