Extrinsic innervation of striatal interneurons and implications for the local microcircuitry -
11 am, seminar room
Invited by David Robbe
Abstract : The classical view on striatal GABAergic interneuron function has been that they operate as independent, parallel, feed-forward inhibitory elements providing inhibitory inputs to SPNs. Much recent evidence has shown that the extrinsic innervation of striatal interneurons is not indiscriminate but rather very specific, and that striatal interneurons are themselves interconnected in a cell-type-specific manner. This suggests that the impact of extrinsic inputs on striatal neuronal activity critically depends on synaptic interactions within interneuronal circuitry. For instance, we recently described the existence of a striatal GABAergic interneuron population (Spontaneously Active Bursty Interneuron; SABIs), receiving cortical and thalamic innervation, which does not seem to innervate the projection neurons, indicating that it may represent the first interneuron-selective interneuron in striatum. Furthermore, we recently showed that the most common response of low threshold spiking interneurons (LTSI) to thalamic stimulation is a disynaptic inhibition through thalamic activation of tyrosine hydroxylase-expressing interneurons (THINs). Further investigation of the excitatory innervation of striatal interneurons show cell-type specific disynaptic inhibitory responses after engagement of the cortex or the thalamus suggesting a high specificity and selectivity in the striatal microcircuitry. In addition, our recent data suggest the existence of a novel source of glutamatergic innervation to the striatum, originating in the pedunculopontine nucleus which selectively targets striatal interneurons, inhibiting the striatal output via feedforward inhibition. Understanding the local striatal connectivity is fundamental to comprehend the integration of the different extrinsic inputs to the striatum.