TAILIEUCHUNG - NEUROVASCULAR MEDICINE - Pursuing Cellular Longevity for Healthy Aging Part 4

Một số nhà khoa học trong lĩnh vực biogerontology cho rằng tuổi già bản thân nó là một loại bệnh và có thể cứu chữa được, mặc dù đây là một vấn đề đang tranh cãi. | 168 PATHWAYS OF CLINICAL FUNCTION AND DISABILITY forebrains have been characterized Zhuo Gebhart 1990a 1990b 1991 1992 1997 Calejesan Kim Zhuo 2000 . Biphasic modulation of spinal nociceptive transmission from the RVM perhaps reflecting the different types of neurons identified in this area offer fine regulation of spinal sensory thresholds and responses. While descending inhibition is primarily involved in regulating suprathreshold responses to noxiousstimuli descending facilitation reduces the neuronal threshold to nociceptive stimulation Zhuo Gebhart 1990a 1990b 1991 1992 1997 . Descending facilitation has a general impact on spinal sensory transmission inducing sensory inputs from cutaneous and visceral organs Zhuo Sengupta Gebhart 2002 Zhuo Gebhart 2002 Zhuo 2007 Fig. . Descending facilitation can be activated under physiological conditions and one physiological function of descending facilitation is to enhance the ability of animals to detect potential dangerous signals in the environment. Indeed neurons in the RVM not only respond to noxious stimuli but also show learning -type changes during repetitive noxious stimuli. More importantly RVM neurons can undergo plastic changes during and after tissue injury and inflammation. ACC-Induced Facilitation It is well documented that the descending endogenous analgesia system including the PAG and RVM plays an important role in modulation of nociceptive transmission and morphine- and cannabinoid-produced analgesia. Neurons in the PAG receive inputs from different nuclei of higher structures including the cingulated ACC. Electrical stimulation of ACC at high intensities up to 500 iA of electrical stimulation did not produce any antinociceptive effect. Instead at most sites within the ACC electrical stimulation produced significant facilitation of the TF reflex . decreases in TF latency . Activation of mGluRs within the ACC also produced facilitatory effects in both anesthetized rats or freely moving mice .

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