Medial prefrontal cortex oxytocin mitigates epilepsy and cognitive impairments induced by traumatic brain injury through reducing neuroinflammation in mice

Examining the Role of Oxytocinergic Signaling and Neuroinflammatory Markers in the Therapeutic Effects of MDMA in a Rat Model for PTSD

MDMA-assisted psychotherapy has shown potential as an effective treatment for post-traumatic stress disorder (PTSD). Preclinical studies involving rodents have demonstrated that MDMA can facilitate the extinction of fear memories. It has been noted that MDMA impacts oxytocin neurons and pro-inflammatory cytokines. Thus, the aim of this study was to explore the role of oxytocinergic signaling and neuroinflammatory markers in the therapeutic effects of MDMA. To achieve this, male rats were subjected to a model of PTSD involving exposure to shock and situational reminders. MDMA was microinjected into the medial prefrontal cortex (mPFC) before extinction training, followed by behavioral tests assessing activity levels, anxiety, and social function. Our findings indicate that MDMA treatment facilitated fear extinction and mitigated the shock-induced increase in freezing, as well as deficits in social behavior. Shock exposure led to altered expression of the gene coding for OXT-R and neuroinflammation in the mPFC and basolateral amygdala (BLA), which were restored by MDMA treatment. Importantly, the OXT-R antagonist L-368,899 prevented MDMA's therapeutic effects on extinction and freezing behavior. In conclusion, MDMA's therapeutic effects in the PTSD model are associated with alterations in OXT-R expression and neuroinflammation, and MDMA's effects on extinction and anxiety may be mediated by oxytocinergic signaling.

Long-Term Impact of Diffuse Traumatic Brain Injury on Neuroinflammation and Catecholaminergic Signaling: Potential Relevance for Parkinson's Disease Risk

Traumatic brain injury (TBI) is associated with an increased risk of developing Parkinson's disease (PD), though the exact mechanisms remain unclear. TBI triggers acute neuroinflammation and catecholamine dysfunction post-injury, both implicated in PD pathophysiology. The long-term impact on these pathways following TBI, however, remains uncertain. In this study, male Sprague-Dawley rats underwent sham surgery or Marmarou's impact acceleration model to induce varying TBI severities: single mild TBI (mTBI), repetitive mild TBI (rmTBI), or moderate-severe TBI (msTBI). At 12 months post-injury, astrocyte reactivity (GFAP) and microglial levels (IBA1) were assessed in the striatum (STR), substantia nigra (SN), and prefrontal cortex (PFC) using immunohistochemistry. Key enzymes and receptors involved in catecholaminergic transmission were measured via Western blot within the same regions. Minimal changes in these markers were observed, regardless of initial injury severity. Following mTBI, elevated protein levels of dopamine D1 receptors (DRD1) were noted in the PFC, while msTBI resulted in increased alpha-2A adrenoceptors (ADRA2A) in the STR and decreased dopamine beta-hydroxylase (DβH) in the SN. Neuroinflammatory changes were subtle, with a reduced number of GFAP+ cells in the SN following msTBI. However, considering the potential for neurodegenerative outcomes to manifest decades after injury, longer post-injury intervals may be necessary to observe PD-relevant alterations within these systems.

Brain Neuropeptides, Neuroinflammation, and Irritable Bowel Syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by chronic abdominal symptoms, but its pathogenesis is not fully understood.

SUMMARY

We have recently shown in rats that neuropeptides such as orexin, ghrelin, and oxytocin act in the brain to improve the intestinal barrier dysfunction, which is a major pathophysiology of IBS. We have additionally shown that the neuropeptides injected intracisternally induced a visceral antinociceptive action against colonic distension. Since it has been known that intestinal barrier dysfunction causes visceral hypersensitivity, the other main pathophysiology of IBS, the neuropeptides act centrally to reduce leaky gut, followed by improvement of visceral sensation, leading to therapeutic action on IBS. It has been recently reported that there is a bidirectional relationship between neuroinflammation in the brain and the pathophysiology of IBS. For example, activation of microglia in the brain causes visceral hypersensitivity. Accumulating evidence has suggested that orexin, ghrelin, or oxytocin could improve neuroinflammation in the CNS. All these results suggest that neuropeptides such as orexin, ghrelin, and oxytocin act in the brain to improve intestinal barrier function and visceral sensation and also induce a protective action against neuroinflammation in the brain.

KEY MESSAGES

We therefore speculated that orexin, ghrelin, or oxytocin in the brain possess dual actions, improvement of visceral sensation/leaky gut in the gut, and reduction of neuroinflammation in the brain, thereby inducing a therapeutic effect on IBS in a convergent manner.