PhD Scientific Days 2024

Poster Session D - Neurosciences 1.

Mapping the Excitatory and Inhibitory Input Structure of the Paraventricular Thalamic Nucleus

Text of the abstract

The paraventricular thalamic nucleus (PVT) is pivotal in regulating emotional and motivational functions by innervating various forebrain areas via excitatory axon collaterals. Modulating PVT activity influences fear, arousal, and stress responses, impacting homeostatic behaviors. Maintaining excitation-inhibition balance is crucial for PVT function, but the sources of its glutamatergic and GABAergic inputs are unclear.

A significant PVT cell population expresses calretinin (CR), serving as a major source of thalamic inputs to the prelimbic cortex, amygdala, and nucleus accumbens, with selective c-Fos expression in response to stress. Whether PVT/CR+ neurons have specific afferent connections is unknown. Thus, our study aimed to address three key questions: i) the origins of excitatory and inhibitory inputs to PVT, ii) the selectivity of these inputs for PVT/CR+ cells, and iii) convergence or segregation of inputs within PVT.

Using retrograde and anterograde viral labeling in vGLUT2-Cre, vGAT-Cre, and vGLUT2-Cre/vGAT-Flp double transgenic mouse strains, we analyzed subcortical inputs. Additionally, Rbp4-Cre, NTSR1-Cre, and FoxP2-Cre strains were utilized to label cortical inputs. Our findings revealed that subcortical afferents to PVT are widely distributed, yet the excitatory and inhibitory inputs mostly segregate, with unique co-innervation from the periaqueductal gray. Furthermore, axons from different subcortical areas overlap, showing high selectivity for CR+ zone in the core PVT region.

In contrast, cortical inputs from layer 5 pyramidal cells target the lateral, transient PVT zone, containing fewer CR+ cells. Cortical inputs to the core region are exclusively found in FoxP2 animals, labeling deep layer 6 cells. These results highlight PVT/CR+ cells integration of information from distinct excitatory and inhibitory subcortical centers. In summary, our data elucidate cortical and subcortical information processing by distinct PVT cell populations.

Supported by the ÚNKP-23-3-I New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.