Cunningham C, Lowry JP (2019) In vivo monitoring of cholinergic neurotransmission with a microelectrochemical choline biosensor. Neuroscience 2019 Abstracts 614.03. Society for Neuroscience, Chicago, IL.
Summary: Acetylcholine acts as a key neuromodulator within the central nervous system, capable of altering neuronal excitability and coordinating neuronal firing patterns. Conversely, cholinergic neurotransmission plays a crucial role in a variety of cognitive functions, including the encoding of new memories. Cholinergic neuronal loss, and the resulting drop in cholinergic neurotransmission (collectively referred to as hypocholinergia), is closely associated with cognitive dysfunction in a number of chronic neurodegenerative disorders including Alzheimer’s disease. However, conventional analytical techniques for monitoring in vivo cholinergic neurotransmission lack the spatiotemporal resolution required to accurately detect endogenous cholinergic dynamics. Here we validate in mice a Pt-based electrochemical biosensor for selective monitoring of choline, a verified marker of cholinergic transmission. Enzymatic choline biosensors (modified with choline oxidase) were sterotaxically implanted in the medial prefrontal cortex (mPFC) and contralateral dorsal hippocampus (dHPC) of female C57Bl6J mice. Real-time choline current recordings over a period of several days revealed circadian fluctuations in both regions, with extracellular choline levels highest during light phases. Administration of pharmacological compounds known to induce central acetylcholine release, scopolamine (1mg/kg) and amphetamine (4mg/kg), evoked a robust increase in choline current. In contrast, peripheral injection of the reversible acetylcholinesterase inhibitor, donepezil (3mg/kg), produced a marked decrease in recorded choline current. The induction of systemic infammation with bacterial lipopolysaccharide (LPS; 500µg/kg) produced characteristic ‘sickness behaviour’ in mice and evoked a tonic rise in central choline levels in both the mPFC and dHPC. Furthermore, the induction of hypocholinergia in selected mice was preformed via intracerebroventricular injections of murine-p75-saporin immunotoxin (1.2µg). Evoked cholinergic neurotransmission was dramatically attenuated in lesioned (hypocholinergic) mice. Collectively, the data suggests that microelectrochemical choline biosensors may serve as a powerful tool for monitoring cholinergic neurotransmission across a number of behavioural and disease states.
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