TNF and Cognitive impairment: Cholecystokinin octapeptide (CCK‐8) alleviated cognitive impairment and promoted glutamatergic synaptogenesis by inhibiting the induction of A1 reactive astrocytes, which was induced by activated microglia‐released tumor necrosis factor alpha (TNF‐α), complement component 1, q subcomponent (C1q) and interleukin 1 alpha (IL‐1α).