Afferent connections of the thalamic nucleus reuniens in the mouse

Abstract

The nucleus reuniens (RE) is part of the midline thalamus and one of the major sources of thalamic inputs to the hippocampal formation and the medial prefrontal cortex. However, it not only sends strong efferents to these areas but is also heavily innervated by both brain regions. Based on its connectivity and supported by functional studies the RE has been suggested to represent a major hub in reciprocal hippocampal–prefrontal communication. Indeed, inactivation studies have demonstrated that this nucleus is particularly important for cognitive behaviors which depend on prefrontal–hippocampal communication, such as working memory or memory consolidation. However, besides its central role in mediating hippocampal–prefrontal communication, the RE is target of a multitude of other cortical and subcortical afferents, which likely modulate its function. So far, however, studies that have systematically investigated the afferents of the RE have only been performed in rats. Because of the unique role of the mouse as a genetically accessible model system for mammalian brain circuit analysis we have mapped the afferent connectivity of the mouse RE using retrograde Fluoro‐Gold tracing. Comparison with similar data from rats indicated a very high level of similarity in prefrontal and hippocampal afferents but some differences in afferent connectivity with other brain regions. In particular, our results suggest interspecies differences regarding the integration of the RE in circuits of fear, aversion, and defense.

A Direct Comparison of Afferents to the Rat Anterior Thalamic Nuclei and Nucleus Reuniens: Overlapping But Different

“…In the present study, these more superficial subiculum cells, although present, were only evident in substantial numbers, when the tracer injection spread beyond nucleus reuniens. The implication, that nucleus reuniens itself is principally innervated by very deep (perialvear) subiculum cells, is supported by two recent mouse studies (Bienkowski et al, 2018;Scheel et al, 2019; see also Mathiasen et al, 2019).…”

Peripheral ERK modulates acupuncture-induced brain neural activity and its functional connectivity

“…Other previous studies also suggested that Sol contributed to the therapeutic effect of acupuncture on inflammation, regulating the GI tract, and relieving pain [54][55][56][57] . The cingulate cortex receives neuronal information from the thalamus and the neocortex, and then projects them to other brain areas of the prefrontal cortex, amygdala, hippocampus, hypothalamus, and midbrain 58,59 . These interconnected prefrontallimbic networks are strongly involved in the formation and processing of emotion, learning, and memory, and these are related to acupuncture signaling transduction, controlling pain, and depression 38,39,60 .…”

Chronic restraint stress induces changes in the cerebral Galpha 12/13 and Rho-GTPase signaling network

“…A certain difference between mice and rats may exist in the organization of brain circuits’ connectivity. For instance, Scheel et al [ 37 ] described the interspecies differences regarding the integration of the nucleus reuniens (a part of the midline thalamus) in circuits of fear, aversion, and defense. The brain stress systems in rats and mice operate on the same bases, and across species there is some universal consistency with respect to brain regions expressing high levels of mineralocorticoid (MR) and glucocorticoid (GR) receptors in adulthood [ 38 , 39 ].…”