Dorsoventral hippocampus distinctly modulates visceral sensitivity and anxiety behaviors in male IBS-like rats

Accumulating evidences suggest dysfunctions in the hippocampus are associated with chronic pain. Nevertheless, the role of hippocampal circuitry in pain memories and emotional responses is not yet fully understood. In this study, we utilized a comprehensive approach that combined electromyography (EMG), photochemical genetic techniques, and anxiety-related behavioral paradigms to investigate the involvement of dorsal hippocampus (DH) and ventral hippocampus (VH) in visceral sensitivity and anxiety behaviors in male rats. Our results demonstrated that IBS-like rats exhibited comorbid visceral hypersensitivity and anxiety, along with the number of activated neurons in the VH was higher than that in the DH. Manipulation of glutamatergic neurons in the hippocampus was identified as a crucial mechanism underlying the mediation of both visceral sensitivity and anxiety behaviors. Specifically, optogenetic activation of the DH induced both visceral hypersensitivity and anxiety, while activation of the VH induced anxiety but did not affect visceral sensitivity. Conversely, chemogenetic inhibition of the DH reduced both visceral hypersensitivity and anxiety, whereas inhibition of the VH alleviated anxiety but did not alleviate visceral hypersensitivity in IBS-like rats. Our study highlights the important role of early life stress in inducing visceral hypersensitivity and anxiety, and further elucidates the distinct functional contributions of the DH and VH to these behavioral changes. These findings provide a theoretical basis for the diagnosis and treatment of IBS, and suggest that targeting specific hippocampal neuron subtypes may represent a promising therapeutic approach.

Partial deletion of p75NTR in large-diameter DRG neurons exerts no influence upon the survival of peripheral sensory neurons in vivo

The p75 neurotrophin receptor (p75NTR ) is required for maintaining peripheral sensory neuron survival and function; however, the underlying cellular mechanism remains unclear. The general view is that expression of p75NTR by the neuron itself is required for maintaining sensory neuron survival and myelination in the peripheral nervous system (PNS). Adopting a neuronal-specific conditional knockout strategy, we demonstrate the partial depletion of p75NTR in neurons exerts little influence upon maintaining sensory neuron survival and peripheral nerve myelination in health and after demyelinating neuropathy. Our data show that the density and total number of dorsal root ganglion (DRG) neurons in 2-month-old mice is not affected following the deletion of p75NTR in large-diameter myelinating neurons, as assessed by stereology. Adopting experimental autoimmune neuritis induced in adult male mice, an animal model of demyelinating peripheral neuropathy, we identify that deleting p75NTR in myelinating neurons exerts no influence upon the disease progression, the total number of DRG neurons, and the extent of myelin damage in the sciatic nerve, indicating that the expression of neuronal p75NTR is not essential for maintaining peripheral neuron survival and myelination after a demyelinating insult in vivo. Together, results of this study suggest that the survival and myelination of peripheral sensory neurons is independent of p75NTR expressed by a subtype of neurons in vivo. Thus, our findings provide new insights into the mechanism underpinning p75NTR -mediated neuronal survival in the PNS.