GABAB receptor‐mediated modulation in the developing dorsal nucleus of the lateral lemniscus

Abstract

AbstractThe dorsal nucleus of the lateral lemniscus (DNLL) is a GABAergic, reciprocally connected auditory brainstem structure that continues to develop postnatally in rodents. One key feature of the DNLL is the generation of a strong, prolonged, ionotropic, GABAA receptor‐mediated inhibition. Possible GABAB receptor‐mediated signalling is unexplored in the DNLL. Here, we used Mongolian gerbils of either sex to describe GABAB receptor‐mediated modulation of postsynaptic potassium currents and synaptic inputs in postnatal (P) animals of days 10/11 and 23–28. Throughout development, we observed the presence of a Baclofen‐activated GABAB receptor‐enhanced potassium outward conductance that is capable of suppressing action potential generation. In P10/11, old gerbils GABAB receptor activation enhances glutamatergic and suppresses ionotropic GABAergic synaptic transmission. During development, this differential modulation becomes less distinct, because in P22–28, old animals Baclofen‐activated GABAB receptors rather enhance ionotropic GABAergic synaptic transmission, whereas glutamatergic transmission is both enhanced and suppressed. Blocking GABAB receptors causes an increase in ionotropic GABAergic transmission in P10/11 old gerbils that was independent on stimulation frequency but depended on the type of short‐term plasticity. Together with the lack of Baclofen‐induced changes in the synaptic paired‐pulse ratio of either input type, we suggest that GABAB receptor‐mediated modulation is predominantly postsynaptic and activates different signalling cascades. Thus, we argue that in DNLL neurons, the GABAB receptor is a post‐synaptically located signalling hub that alters signalling cascades during development for distinct targets.