The Journal of comparative neurology
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Periglomerular (PG) cells in the rodent olfactory bulb are heterogeneous anatomically and neurochemically. Here we investigated whether major classes of PG cells use gamma-aminobutyric acid (GABA) as a neurotransmitter. In addition to three known subtypes of PG cells expressing tyrosine hydroxylase (TH), calbindin D-28k (CB), and calretinin (CR), we identified a novel PG cell population containing the GABAA receptor alpha5 subunit. ⋯ In addition, CB-, CR-, and TH-positive dendrites were apposed to GABAA receptor clusters containing the alpha1 or alpha3 subunits, which are found in mitral and tufted cells, and the alpha2 subunit, which is expressed by PG cells. Together, these findings indicate that all major subtypes of PG cells are GABAergic. In addition, they show that PG cells provide GABAergic input to the dendrites of principal neurons and are interconnected with other GABAergic interneurons, which most likely are other PG cells.
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The actions of Reelin in neuronal positioning in the developing cortex and cerebellum are relayed by Src-family kinase (SFK)-mediated phosphorylation of Dab1. Biochemical studies show that after phosphorylation Dab1 binds to an adaptor protein, CrkL. Whether CrkL is important for Reelin signaling in vivo is unknown, because crkl(-/-) embryos die before cortical development is complete. ⋯ These results show that tyrosine phosphorylation of Dab1 by SFKs is required for Reelin-regulated SPN positioning. In addition, we found that SPN migration in crkl(-/-) showed a partial reeler phenotype, suggesting a partial loss of response of SPN to Reelin signaling. These results suggest a role for CrkL in the Reelin signaling pathway to control neuronal migration.