The Neural Circuit Between Dorsal Striatum And Thalamic Reticular Nucleus

Thalamic Reticular Nucleus originates from the ventral thalamus and locates between the cortex and thalamus. It is mainly composed of GABAergic parvalbumin (PV) neurons. Cortex and thalamus, globus pallidus, pars externa (GPe), and brainstem project to TRN with the glutamatergic, GABAergic and cholinergic respectively. TRN plays important roles in the modulation of sleep, selective attention, vigilance. Findings from the cellular and network study found the key roles of TRN during various states of consciousness. It is necessary to reveal the complex function of TRN through the neural circuit research.Striatum is one of the main input nucleus of the basal ganglia, the diseases due to the function impairment of striatum showed that the importance of the striatum in basal ganglia. Study the striatum neural circuit and physiological functions can effectively explain the striatum in maintaining health and leading to disease.The Striatum can be divided into two parts:the dorsal and ventral striatum. Striatum is composed of two kinds of neurons:Medium spiny projection neurons (MSN) and Interneuron. We found the distance of dorsal striatum and Thalamic Reticular Nucleus (TRN) is very short on the anatomical structure and separated only by internal capsule. TRN contacts the cortex and thalamus and accepts the projection of the cortex and the thalamus, with that of the striatum is similar to the relationship between the cortex and the thalamus. Based on these phenomena, we are interested in whether there is direct link between striatum and TRN. We didn’t found any research about this. So, we took advantage of the retrograde rabies virus combination with electrophysiology, optogenetics to answer this question, we injected the retrograde rabies virus in the dorsal of TRN, and found the input cell which project to TRN in the dorsal Striatum. And then we injected AAV which contains ChR2 and mCherry in the dorsal striatum of Dlx5/6-Cre and A2A-Cre mice. In Dlx5/6-Cre but A2A-Cre mice, we found the projection terminals in TRN dorsal area. We speculate that the direct pathway MNS but indirect pathway MSN project to TRN. In order to confirm this result, we did electrophysiology experiment using Dlx5/6-Cre mice. After given the partial light stimulation in TRN area, we didn’t record corresponding electrophysiological activities. We suspect that one of the reason is the virus we injected in Dlx5/6-Cre striatum wasn’t enough to induced response another is the terminals projecting to TRN was cut off through the coronal section. Aiming at this situation, we will use D1-Cre mice and more efficiently virus to confirm enough MSN was infected, and recording in the sagittal section brain slice. According our results, we summarize as follows:1) we confirmed the projection from dorsal striatum to TRN using the retrograde virus; 2) It is the direct MSN but indirect MSNs project to TRN; 3) we should improve the experiment to confirm the result at the level of electrophysiology.