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Title: Effects of Posterior hypothalmic lesions on formalin-induced pain behaviours
Keywords: Posterior hypothalamus, supramammillary, affective-motivational, formalin, pain, nociception
Issue Date: 26-Jul-2010
Citation: LIU LIMENG (2010-07-26). Effects of Posterior hypothalmic lesions on formalin-induced pain behaviours. ScholarBank@NUS Repository.
Abstract: The posterior hypothalamus (PH)-supramammillary (SuM) region connects to variety of regions in the CNS, some of which influence affective-motivational behaviors. For example, the region is reciprocally connected to the hippocampal formation. The hippocampal formation is crucial for adaptive behaviors and, importantly, contributes to the negative affective-motivational state during pain. In the present study we explored whether PH-SuM as well modulate animal pain behaviors in the formalin model of persistent inflammatory pain. Formalin (1.25%, 0.1ml) was injected subcutaneously into the plantar surface of the right hind paw of PH-SuM lesioned or control non-lesioned animals. The lesion was induced by microinjection of the glutamate receptor ligand, a-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA, 0.99ng in 0.3¿l). The lesioned animals were subdivided into a `dorsal lesion group¿ and a ventral lesion group based on the affected area visualized using OX42 immunocytochemistry as a marker for microglia activation. The damaged area in the dorsal lesion group included the PH and adjacent areas, whereas the ventral lesion extended into the lateral SuM. The lesioned area was bilateral or either ipsilateral or contralateral to the injected paw. The lesion of SuM was incomplete. Neither dorsal nor ventral lesion affected animal behavior in open field. Interestingly, ventral lesion encompassing the lateral SuM attenuated animal behavior to formalin. The effect was more marked during the later part of the formalin response leading to truncated duration of formalin pain-induced behaviors. An effect was also seen with dorsal lesion but was not as marked. These trends raise the possibility that PH-SuM region, especially ventrally influence the affective-motivational drive to pain.
Appears in Collections:Master's Theses (Open)

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