Specific [3H]strychnine binding associated with glycine receptors in bovine retina

Saturable, specific [3H]strychnine binding can be demonstrated in homogenates of bovine retina. Scatchard plots revealed only one set of binding sites with a dissociation constant (Kd) of about 60 nM and a maximal number of binding sites of about 1.5 pmol/mg protein. The structural specificity of [3H]strychnine binding sites in bovine retina parallels the properties found for [3H]strychnine binding sites in the spinal cord of several vertebrates. Thus, the data do not give any evidence that specific [3H]strychnine binding in bovine retina labels taurine rather than glycine receptors and favors glycine rather than taurine as inhibitory neurotransmitter in bovine retina. The subcellular distribution of specific [3H]strychnine binding in bovine retina parallels that of sodium-dependent, high-affinity uptake of glycine and taurine. All 3 parameters are mainly found in the P2 fractions of bovine retina homogenates, containing conventional synaptosomes, most abundant in the inner plexiform layer, but can also be found in the P1 fractions, containing large synaptosomes from the photoreceptor cell layer.