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Effects of an orexin-2 receptor agonist on attention in rats following loss of cortical cholinergic projections

Blumenthal SA, Maness EBL, Fadel JR, Burk JA (2019) Effects of an orexin-2 receptor agonist on attention in rats following loss of cortical cholinergic projections. Neuroscience 2019 Abstracts 418.06. Society for Neuroscience, Chicago, IL.

Summary: Deterioration to the basal forebrain cholinergic system (BFCS) is linked to age-related cognitive impairment, specifically to the pathology of Alzheimer’s disease (AD). Animals with BFCS damage perform poorly on learning, memory, and attention tasks, indicating cognitive deficits. The orexin neuropeptide system, comprised of two neuropeptides (orexin A and orexin B), has also been implicated in the cognitive decline associated with aging, likely due to the role of orexins in promoting attention. Two orexin receptor subtypes exist, orexin 1 (Ox1R) and orexin 2 (Ox2R). Studies have examined the effects of stimulation and blockage of both receptors together and Ox1R alone on attention; but no studies have examined the role of Ox2Rs in attention through the use of Ox2R agonists. Ox2Rs may be implicated in attentional processes and the loss of orexin neurons seen in age-related cognitive decline. In order to examine the role of Ox2Rs in attention following BFCS deterioration, the present study administered the Ox2R agonist, YNT-185, to rats given intrabasalis infusions of either saline (n = 12) or 192 IgG saporin (n=11), an immunotoxin which selectively destroys the BFCS. Animals received infusions of YNT-185 to the lateral ventricle (LV) in doses of 0, 1, 10, and 100nM across four separate sessions and performance was then assessed on a sustained attention task requiring discrimination between signal and non-signal trials through lever presses. The 100nM dose of YNT-185 improved attentional performance, as compared to the 0nM dose, for rats given the immunotoxin, but worsened performance for rats given saline lesions. YNT-185 may be efficacious in aiding attentional function in animals with vulnerable cholinergic systems but may lead to overexcitation for those with intact cholinergic function.

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