Glutamate receptor binding to cat central nervous system membranes
L-[3H]Glutamate exhibited specific binding to fresh membranes of cat CNS under physiological conditions of pH and temperature. This binding occurred in the absence of sodium ions. Kinetic analysis of the data for cerebellum suggested the presence of two distinct binding sites: a high-affinity process (Kd = 0.33 μM) with a capacity of 15 pmol/mg protein and a low-affinity process (Kd = 1.8 μM) which had a capacity of 65 pmol/mg protein. Several structural analogues of glutamic acid were able to appreciably inhibit the binding of [3H]glutamate. The distribution of glutamate binding between 12 regions of the CNS was measured. The amygdaloid complex exhibited the highest binding followed by hippocampus > hypothalamus ≡ visual cortex ≡ thalamus ≡ caudate nucleus > olfactory bulb ≡ tectum ≡ cerebellum > dorsal pons ≡ medulla > cervical spinal cord. These findings are consistent with the binding of [3H]glutamate being to its receptor.