Graded heterogeneity of metabotropic signaling underlies a continuum of cell-intrinsic temporal responses

Abstract

Many neuron types consist of populations with continuously varying molecular properties. Here we show a continuum of postsynaptic molecular properties in three types of neurons and assess the functional consequences in cerebellar unipolar brush cells (UBCs). While UBCs are thought to form discrete functional subtypes, with mossy fiber (MF) activation increasing firing in ON-UBC and suppressing firing in OFF-UBC. We find instead a continuum of response profiles that reflect the graded and inversely correlated expression of excitatory mGluR1 and inhibitory mGluR2/3 pathways. MFs coactivate mGluR2/3 and mGluR1 in many UBCs, leading to sequential inhibition-excitation because mGluR2/3-currents are faster. Additionally, we show that DAG kinase controls mGluR1 response duration, and that graded DAG kinase levels account for systematic variation of response duration over two orders of magnitude. These results demonstrate that continuous variations in metabotropic signaling can generate a stable cell-autonomous basis for temporal integration and learning over multiple time scales.