The paraventricular nucleus of the thalamus: a hub in the neural network for fear and anxiety

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Date
2020-06
Authors
Dong, Xinwen
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Abstract
The paraventricular nucleus of the thalamus (PVT) is a part of a group of the midline and intralaminar thalamic nuclei. The PVT receives and sends projections to brain regions essential for fear and anxiety indicating that the PVT may be a critical hub in the brain's fear and anxiety network. This thesis presents a series of studies investigating the involvement of the PVT and its projection in fear and anxiety. The first study showed that lesions of the PVT attenuated the expression of conditioned fear while blocking orexin receptors in the PVT had no effect on fear but reduced anxiety. These findings can be potentially viewed as evidence that the PVT regulates different defensive responses independently via unique groups of neurons that project to different basal forebrain nuclei. The second study used a dual-retrograde-tracing strategy to determine whether the PVT contains distinct subpopulations of neurons that project to the shell of the nucleus accumbens (NAcSh), the dorsolateral part of the bed nucleus of the stria terminalis (BSTDL), and the lateral part of the central nucleus of the amygdala (CeL). This study revealed that most neurons in the PVT innervate the NAcSh and that many neurons project to more than one brain region. In addition, PVT neurons that project to the NAcSh, BSTDL, or CeL did not appear to be activated differentially when rats were exposed to footshocks or an open field. These results suggest that the PVT may contribute to stress-induced fear and anxiety through its projection to the NAcSh. The third study examined the involvement of the PVT-NAcSh projection in fear and anxiety using an intersectional chemogenetic technique. The result showed that selective inhibition of PVT neurons that innervate NAcSh reduced footshock-induced social anxiety in susceptible rats but not conditioned fear. In summary, experiments in this thesis demonstrate that the PVT contributes to conditioned fear and stress-induced anxiety and point to the possibility that the PVT may coordinate defensive responses by acting on the NAcSh, BSTDL, and CeL.
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Keywords
Paraventricular nucleus of the thalamus, Anxiety, Fear, Emotion, Nucleus accumbens, Chemogenetic
Citation
Dong, X., Li, Y., & Kirouac, G. J. (2015). Blocking of orexin receptors in the paraventricular nucleus of the thalamus has no effect on the expression of conditioned fear in rats. Frontiers in Behavioral Neuroscience, 9(June), 161. https://doi.org/10.3389/fnbeh.2015.00161
Dong, X., Li, S., & Kirouac, G. J. (2017). Collateralization of projections from the paraventricular nucleus of the thalamus to the nucleus accumbens, bed nucleus of the stria terminalis, and central nucleus of the amygdala. Brain Structure and Function, 222(9), 3927–3943. https://doi.org/10.1007/s00429-017-1445-8
Li, Y., Dong, X., Li, S., & Kirouac, G. J. (2014). Lesions of the posterior paraventricular nucleus of the thalamus attenuate fear expression. Frontiers in Behavioral Neuroscience, 8(March), 94. https://doi.org/10.3389/fnbeh.2014.00094