Galanin immunohistochemistry was carried out in the anterior nucleus basalis of Meynert of 27 Parkinson's disease (PD) cases without cognitive impairment (mild cognitive impairment [MCI]), 15 with PD with MCI, 42 with Parkinson's disease dementia (PDD), 12 with Dementia with Lewy bodies (DLB), 19 with AD, 12 mixed AD/DLB and 16 controls.
On the other hand, current data suggest that galanin and its agonists (M617, M1145 and M1153) manifest the characters of anti-insulin resistance, anti-Alzheimer's disease and ameliorate or reinforce depression-like behavior.
GAL fiber hyperinnervation of cholinergic NB neurons upregulates the expression of ChAT, the synthetic enzyme for ACh, suggesting that GAL regulates the cholinergic tone of CBF neurons in AD.
These observations indicate that GAL hypertrophy within the anterior NB subfield is a late-stage AD response, which may play a role in regulating the cholinergic tone of remaining basocortical projection neurons.
Moreover, studies using mice transgenic for both the amyloid precursor protein (APP) and presenilin-1 (PS1) bearing AD-related mutations (APPswe/PS1delta9) displayed increased GAL immunoreactive fibers, neurities and plaques in cortex and hippocampus.
These findings raise the possibility that the increased incidence of GAL expression among remaining LC neurons contributes to the hyperinnervation of GAL fibers in AD.
Galanin (GAL) is a biologically active neuropeptide that has been suggested to play a role in stress-induced inhibition of insulin secretion, in dementia of the Alzheimer's type, and in the regulation of growth hormone secretion.