DEVELOPMENTAL AND SENSORY-DEPENDENT CHANGES OF PHOSPHOINOTSITIDE-LINKED METABOTROPIC GLUTAMATE RECEPTORS

Metabotropic glutamate receptors (mGluRs) can modulate synaptic transm ission, and there is evidence that phosphoinositide (PI)-linked mGluRs may be involved in sensory-dependent plasticity during the developmen t of cat visual cortex. Consequently, we asked the questions: Where ar e the PI-linked mGluRs (mGluR1 alpha and mGluR5) in the visual cortex? Does the quantity and distribution of these receptors change in the c at visual cortex during postnatal development, and are these features sensory-dependent? We found that the quantity of mGluR1 alpha decrease s with age, whereas the laminar distribution of mGluR1 alpha remains t he same. Quantity of mGluR5 also decreases, but the laminar distributi on of mGluR5 changes during development. The pattern and timing of the mGluR5 change in distribution follow the development of geniculocorti cal afferents. Immunostaining indicates that reduction of receptor occ urs mainly in layers V-VI for mGluR1 alpha and outside layer IV for mG luR5. Dark-rearing postpones the laminar change of mGluR5 and produces an increased level of mGluR5 between postnatal 1.5-6 weeks of age but has no significant effect on the mGluR1 alpha distribution or the mGl uR1 alpha quantity. These results suggest that mGluR1 alpha and mGluR5 are involved in different aspects of cortical development. The mGluR5 is more likely to be involved in sensory-dependent events than mGluR1 alpha. The lack of developmental correlation between mGluR quantities and the critical period for ocular dominance plasticity also suggests that other factors besides mGluR quantities are important for ocular dominance plasticity. (C) 1997 Wiley-Liss, Inc.