Amnesia is the inability to store new information and recall old memories. After the postulation of
cholinergic hypothesis of geriatric memory dysfunction, the
cholinergic signaling became a popular target to understand the underlying molecular mechanism of
amnesia and its recovery.
Scopolamine is a non-selective
cholinergic receptor antagonist and induces
amnesia through downregulation of synaptic plasticity genes including immediate early genes (IEGs).
Scopolamine-induced amnesic mouse model is widely used to study the memory impairment that mimics the pathophysiology of aging, neurodegenerative, and neuropsychiatric disorders. However, a detailed understanding of
cholinergic signaling-mediated regulation of plasticity-related gene expression remains elusive. Therefore, we have investigated the role of
muscarinic acetylcholine receptors (mAChRs) and their downstream mediator
protein kinase C (PKC) in the regulation of IEGs expression in amnesic mice hippocampus.
Pilocarpine, a mAChRs agonist, was used to activate the
cholinergic signaling in
scopolamine-induced
amnesia. Further, a PKC activator
bryostatin 1 was used to understand the sole involvement of PKC as a downstream mediator of mAChRs-mediated signaling.
Pilocarpine treatment significantly restored the
scopolamine-induced impaired recognition memory and downregulated hippocampal IEGs expression and phosphorylation of ERK1/2 (
extracellular signal-regulated kinase 1/2) and CREB (
cAMP response element-binding protein). On the other hand, the
bryostatin 1-mediated activation of PKC in
scopolamine-induced
amnesia selectively restored the hippocampal IEGs expression, recognition memory, and phosphorylation of ERK1/2 and CREB. Taken together, our findings suggest that mAChRs and their downstream mediator PKC regulate the hippocampal IEGs expression and ERK1/2-mediated CREB phosphorylation in
scopolamine-induced amnesic mice.