Abstract
The properties of glycine receptors (GlyRs) depend upon their subunit composition. While the prevalent adult forms of GlyRs are heteromers, previous reports suggested functional alpha homomeric receptors in mature nervous tissues.
Here we show two functionally different GlyRs populations in the rat medial nucleus of trapezoid body (MNTB). Postsynaptic receptors formed alpha 1/beta-containing clusters on somatodendritic domains of MNTB principal neurons, colocalizing with glycinergic nerve endings to mediate fast, phasic IPSCs.
In contrast, presynaptic receptors on glutamatergic calyx of Held terminals were composed of dispersed, homomeric alpha 1 receptors. Interestingly, the parent cell bodies of the calyces of Held, the globular bushy cells of the cochlear nucleus, expressed somatodendritic receptors (alpha 1/beta heteromers) and showed similar clustering and pharmacological profile as GlyRs on MNTB principal cells.
These results suggest that specific targeting of GlyR beta-subunit produces segregation of GlyR subtypes involved in two different mechanisms of modulation of synaptic strength.