albuquerque2009 1.0.0

KYNA is formed enzymatically by the irreversible transamination of L-kynurenine, a major peripheral tryptophan metabolite with ready access to the brain. Immunohistochemical and lesion studies demonstrated that cerebral KYNA synthesis takes place almost exclusively in astrocytes (129, 187, 199). PubMed:19126755

A link between alpha4 nAChRs and Cox2 was suggested by the observation that interneurons in the hippocampus coexpress both proteins (165). A mechanistic connection was inferred when long-term treatment of aged animals with NS398 promoted retention of alpha4 nAChR expression in the brain, an effect that was antagonized by the coadministration of nicotine. PubMed:19126755

Other endogenous ligands that impact on the activity of nAChRs noncompetitively and voltage independently include the amyloid beta peptide 1-42 (Abeta1-42; Refs. 123, 376) and the canabinoid anandamide (356, 442). PubMed:19126755

It is noteworthy that the alpha7 nAChR activity increases intracellular accumulation of Abeta in neurons (336), and Abeta peptides, in addition to modulating nAChR activity, downregulate the expression of nAChRs (197). PubMed:19126755

The Abeta1-42 peptide is one of the breakdown products of the proteolytic cleavage of the amyloid precursor protein by beta- and gamma-secretases. In biopsy samples of human brain tissue obtained from AD patients and in ectopic systems overexpressing either alpha7 nAChRs or APP, Abeta1-42 coimmunoprecipitates with alpha7 nAChRs (490). The Abeta1-42 peptide also displaces binding of [3H]MLA from alpha7 nAChRs in cerebral cortical and hippocampal synaptosomes (490). PubMed:19126755