Administration of amyloid-ß oligomer to the buccal ganglia may reduce food intake and cholinergic synaptic responses within the feeding neural circuit in Aplysia kurodai.

Anorexia is a behavioral change caused by functional brain disorders in patients with Alzheimer's disease (AD). Amyloid-ß (1-42) oligomers (o-Aß) are possible causative agents of AD that impair signaling via synaptic dysfunction. In this study, we used Aplysia kurodai to study functional disorders of the brain through o-Aß. Administration of o-Aß to the buccal ganglia (feeding brain for oral movements) by surgical treatment significantly reduced food intake for at least five days. Furthermore, we explored the effects of o-Aß on the synaptic function in the feeding neural circuit, focusing on a specific inhibitory synaptic response in jaw-closing motor neurons produced by cholinergic buccal multi-action neurons because we recently found that this cholinergic response decreases with aging, which is consistent with the cholinergic hypothesis for aging. Administration of o-Aß to the buccal ganglia significantly reduced the synaptic response within minutes, whereas administration of amyloid-ß (1-42) monomers did not. These results suggest that o-Aß may impair the cholinergic synapses, even in Aplysia, which is consistent with the cholinergic hypothesis for AD.