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Luo Y, Wang Y, Qiu F, Hou G, Liu J, Yang H, Wu M, Dong X, Guo D, Zhong Z, Zhang X, Ge J, Meng P. Ablated Sonic Hedgehog Signaling in the Dentate Gyrus of the Dorsal and Ventral Hippocampus Impairs Hippocampal-Dependent Memory Tasks and Emotion in a Rat Model of Depression. Mol Neurobiol 2024; 61:4352-4368. [PMID: 38087166 DOI: 10.1007/s12035-023-03796-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 11/08/2023] [Indexed: 07/11/2024]
Abstract
Specific memory processes and emotional aberrations in depression can be attributed to the different dorsal-ventral regions of the hippocampus. However, the molecular mechanisms underlying the differential functions of the dorsal hippocampus (dHip) and ventral hippocampus (vHip) remain unclear. As Sonic Hedgehog (Shh) is involved in the dorsal-ventral patterning of the neural tube and its signaling is dysregulated by chronic unpredictable mild stress (CUMS), we investigated its role in influencing the differential functions of the dHip and vHip. Here, CUMS downregulated the expression of Shh signaling markers, including Shh and its downstream effectors GLI family zinc finger 12 (Gli1/2), Patched (Ptch), and smoothened (Smo), in both the dHip and vHip of rats, though more so in the vHip. Additionally, Shh knockdown in the dorsal or ventral dentate gyrus (DG) resulted in restrained neurogenic activity in newborn neurons, especially in immature neurons through decreased expression of Shh signaling markers. Furthermore, Shh knockdown in the DG of the dHip led to memory impairment by inhibiting experience-dependent activation of immature neurons, whereas its knockdown in the DG of the vHip led to an emotional handicap by delaying the maturation of immature neurons. Finally, Shh knockdown in either the dDG or vDG of hippocampus abolished the corresponding cognitive enhancement and emotional recovery of fluoxetine. In conclusion, Shh is essential to maintain the functional heterogeneity of dHip and vHip in depressed rat, which was mainly mediating by local changes of dependent activation and maturity of immature neurons, respectively.
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Affiliation(s)
- Yan Luo
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
| | - Yan Wang
- Yiyang Central Hospital, Yiyang, 413000, Hunan, China
| | - Feng Qiu
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
| | - Guanghan Hou
- Fourth Hospital of Changsha, Hunan, 410000, China
| | - Jian Liu
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
- First Affiliated Hospital, Hunan University of Chinese Medicine, Changsha, 410007, Hunan, China
| | - Hui Yang
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
- First Affiliated Hospital, Hunan University of Chinese Medicine, Changsha, 410007, Hunan, China
| | - Mei Wu
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
| | - Xuanqi Dong
- The Second People's Hospital of Hunan Province, Changsha, 410000, Hunan, China
| | - Dongwei Guo
- The Second People's Hospital of Hunan Province, Changsha, 410000, Hunan, China
| | - Ziyan Zhong
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China
| | - Xi Zhang
- The Second People's Hospital of Hunan Province, Changsha, 410000, Hunan, China.
| | - Jinwen Ge
- Hunan Academy of Chinese Medicine, Changsha, 410300, Hunan, China.
| | - Pan Meng
- Hunan University of Chinese Medicine, Changsha, 410208, Hunan, China.
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Kempermann G. What Is Adult Hippocampal Neurogenesis Good for? Front Neurosci 2022; 16:852680. [PMID: 35495058 PMCID: PMC9051245 DOI: 10.3389/fnins.2022.852680] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/17/2022] [Indexed: 12/29/2022] Open
Abstract
Adult hippocampal neurogenesis is a unique and exceptional process in the mammalian brain that in a lifelong and activity-dependent way generates new excitatory principal neurons. A comprehensive view on their function in greater contexts has now emerged, revealing to which extent the hippocampus (and hence brain and mind) depend on these neurons. Due to a postmitotic period of heightened synaptic plasticity they bias incoming excitation to the dentate gyrus to non-overlapping subnetworks, resulting in pattern separation and the avoidance of catastrophic interference. Temporally, this promotes the flexible integration of novel information into familiar contexts and contributes to episodic memory, which in humans would be critical for autobiographic memory. Together these local effects represent a unique strategy to solve the plasticity-stability dilemma that all learning neuronal networks are facing. Neurogenesis-dependent plasticity also improves memory consolidation. This relates to the surprising involvement of adult neurogenesis in forgetting, which is also hypothesized to be critically relevant for negative plasticity, for example in post-traumatic stress disorder. In addition, adult-born neurons also directly mediate stress-resilience and take part in affective behaviors. Finally, the activity- and experience-dependent plasticity that is contributed by adult neurogenesis is associated with an individualization of the hippocampal circuitry. While a solid and largely consensual understanding of how new neurons contribute to hippocampal function has been reached, an overarching unifying theory that embeds neurogenesis-dependent functionality and effects on connectomics is still missing. More sophisticated multi-electrode electrophysiology, advanced ethologically relevant behavioral tests, and next-generation computational modeling will let us take the next steps.
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Affiliation(s)
- Gerd Kempermann
- German Center for Neurodegenerative Diseases (DZNE), Dresden, Germany
- Center for Regenerative Therapies Dresden (CRTD), Technische Universität Dresden, Dresden, Germany
- *Correspondence: Gerd Kempermann, ;
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