Thalamic nucleus reuniens regulates spatial memory via medial entorhinal cortex: a preliminary study

Abstract

Objective To preliminarily investigate the role of thalamic nucleus reuniens (RE) on medial entorhinal cortex (MEC)-related spatial memory and its mechanism. Methods Retrobeads-mediated retrograde tracing and anterograde tracing were used to identify the morphological connections between RE and MEC brain regions. Then in vivo fiber photometry was used to record and analyze the activities of REMEC-projecting neurons when mice were exploring in the open field. Chemical genetics was utilized to explore the effects of RE-MEC pathway inhibition on spatial memory. Results Retrograde and anterograde tracing confirmed that RE sent neuronal fibers to MEC, which were mainly distributed in the superficial layers. Optical fiber recording showed that the activities of REMEC-projecting neurons were increased when the mice were rearing and looking up, but were decreased when the mice were stationary and grooming (R2=0.077 3, P < 0.01). And the calcium signal of these neurons was positively correlated with movement speed. Compared with the control group, chemogenetic inhibition of the RE-MEC pathway significantly prolonged the exploration distance of the mice in the treatment group in the open field (P < 0.01), but showed no effects on the center time, rearing time, number of head ups and number of grooming. Conclusion RE-MEC pathway is activated during spatial exploratory behaviors and participates in spatial learning and memory. Chemogenetic inhibition of RE-MEC pathway impairs spatial memory and extends the exploration distance to represent the spatial information of novel environment, and has no effects on emotions. [Key words] thalamic nucleus reuniens , medial entorhinal cortex , spatial memory , open field ,

Keywords

• thalamic nucleus reuniens
• medial entorhinal cortex
• spatial memory
• open field