Ontogenetic Changes in Glial Fibrillary Acid Protein Phosphorylation, Glutamate Uptake and Glutamine Synthetase Activity in Olfactory Bulb of Rats

Abstract

Phosphorylation of the glial fibrillary acidic protein (GFAP) in hippocampal and cerebellar slices from immature rats is stimulated by glutamate. This effect occurs via a group II metabotropic glutamate receptor in the hippocampus and an NMDA ionotropic receptor in the cerebellum. We investigated the glutamate modulation of GFAP phosphorylation in the olfactory bulb slices of Wistar rats of different ages (post-natal day 15 = P15, post-natal day 21 = P21 and post-natal day 60 = P60). Our results showed that glutamate stimulates GFAP phosphorylation in young animals and this is mediated by NMDA receptors. We also observed a decrease in glutamate uptake at P60 compared to P15, a finding similar to that found in the hippocampus. The activity of glutamine synthetase was elevated after birth, but was found to decrease with development from P21 to P60. Together, these data confirm the importance of glutamatergic transmission in the olfactory bulb, its developmental regulation in this brain structure and extends the concept of glial involvement in glutamatergic neuron-glial communication.

Study of the glial cytoarchitecture of the developing olfactory bulb of a shark using immunochemical markers of radial glia

“…With regard the numerous GS-positive cells and processes observed in the granular and glomerular layers of embryonic and juvenile catsharks (present results), they are probably involved in the regulation of glutamate transmission at these places. In glutamatergic synapses, most of the glutamate released to the synaptic cleft is taken up by astrocytes, where is transformed to glutamine by the action of the enzyme GS (Battú et al 2005). In the mammalian OB, GABA uptake from the synaptic cleft by astrocytes is also involved in neuron-glia signalling (Doengi et al 2009).…”