Heterogeneity of glycine receptors and their messenger RNAs in rat brain and spinal cord

Messenger RNAs isolated from adult or newborn rat spinal cord were fractionated in a sucrose gradient. The fractions were injected into Xenopus oocytes to determine their potencies for expression of glycine receptors (GlyRs), which were then examined electrophysiologically. The sedimentation profiles disclosed two classes of GlyR mRNAs, one heavy and the other light. The adult spinal cord was rich in heavy GlyR mRNA, whereas the light GlyR mRNA was more abundant in neonatal spinal cord and in adult cerebral cortex. Glycine receptors encoded by heavy and light mRNAs of adult spinal cord showed some electrophysiological differences. Thus there are two types of GlyRs encoded by mRNAs of different sizes, and the expression of these mRNAs is developmentally regulated. A tissue- and age-dependent distribution of heterogeneous GlyR mRNAs may imply diverse roles of the GlyRs in neuronal function in the central nervous system.