Browsing by Author "Wu, Long-Jun"

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    Enhanced presynaptic neurotransmitter release in the anterior cingulate cortex of mice with chronic pain
    (Society for Neuroscience, 2006-08-30) Zhao, Ming-Gao; Ko, Shanelle W.; Wu, Long-Jun; Toyoda, Hiroki; Xu, Hui; Quan, Jessica; Li, Jianguo; Jia, Yongheng; Ren, Ming; Xu, Zao C.; Zhuo, Min; Anatomy and Cell Biology, School of Medicine
    The anterior cingulate cortex (ACC) is a forebrain structure known for its roles in learning and memory. Recent studies show that painful stimuli activate the prefrontal cortex and that brain chemistry is altered in this area in patients with chronic pain. Components of the CNS that are involved in pain transmission and modulation, from the spinal cord to the ACC, are very plastic and undergo rapid and long-term changes after injury. Patients suffering from chronic pain often complain of memory and concentration difficulties, but little is known about the neural circuitry underlying these deficits. To address this question, we analyzed synaptic transmission in the ACC from mice with chronic pain induced by hindpaw injection of complete Freund's adjuvant (CFA). In vitro whole-cell patch-clamp recordings revealed a significant enhancement in neurotransmitter release probability in ACC synapses from mice with chronic pain. Trace fear memory, which requires sustained attention and the activity of the ACC, was impaired in CFA-injected mice. Using knock-out mice, we found that calmodulin-stimulated adenylyl cyclases, AC1 and/or AC8, were crucial in mediating the long-lasting enhanced presynaptic transmitter release in the ACC of mice with chronic pain. Our findings provide strong evidence that presynaptic alterations caused by peripheral inflammation contribute to memory impairments after injury.
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    Integrated Feedforward and Feedback Mechanisms in Neurovascular Coupling
    (Wolters Kluwer, 2024-12) Meng, Lingzhong; Rasmussen, Mads; Meng, Deyi M.; White, Fletcher A.; Wu, Long-Jun; Anesthesia, School of Medicine
    Neurovascular coupling (NVC) is the mechanism that drives the neurovascular response to neural activation, and NVC dysfunction has been implicated in various neurologic diseases. NVC is driven by (1) nonmetabolic feedforward mechanisms that are mediated by various signaling pathways and (2) metabolic feedback mechanisms that involve metabolic factors. However, the interplay between these feedback and feedforward mechanisms remains unresolved. We propose that feedforward mechanisms normally drive a swift, neural activation–induced regional cerebral blood flow (rCBF) overshoot, which floods the tissue beds, leading to local hypocapnia and hyperoxia. The feedback mechanisms are triggered by the resultant hypocapnia (not hyperoxia), which causes cerebral vasoconstriction in the neurovascular unit that counterbalances the rCBF overshoot and returns rCBF to a level that matches the metabolic activity. If feedforward mechanisms function improperly (eg, in a disease state), the rCBF overshoot, tissue-bed flooding, and local hypocapnia fail to occur or occur on a smaller scale. Consequently, the neural activation–related increase in metabolic activity results in local hypercapnia and hypoxia, both of which drive cerebral vasodilation and increase rCBF. Thus, feedback mechanisms ensure the brain milieu’s stability when feedforward mechanisms are impaired. Our proposal integrates the feedforward and feedback mechanisms underlying NVC and suggests that these 2 mechanisms work like a fail-safe system, to a certain degree. We also discussed the difference between NVC and cerebral metabolic rate-CBF coupling and the clinical implications of our proposed framework.