Fotocontrollo dell'attività del recettore colinergico M1

The cholinergic system is often targeted for the treatment of several pathophysiological conditions (e.g. Alzheimer´s disease), because acetylcholine (ACh) modulates many cellular functions. ACh exerts its role as neurotransmitter and neuromodulator, acting on two different types of receptors: nicotinic acetylcholine receptors (nAChRs) and muscarinic acetylcholine receptors (mAChRs). The latter are metabotropic receptors with having five distinct muscarinic subtypes (M1R-M5R) identified. Both nAChRs and mAChRs are expressed in the central nervous system (CNS) and peripheral nervous system (PNS), modulating specific processes depending on their location. Many muscarinic agonists failed in clinical trials, because of their poor selectivity of action and displayed various adverse effects. In contrast, muscarinic selective antagonists, which are clinically approved, seem to be more effective and less harmful than non-selective ones. In addition, the traditional pharmacology is unable to control drug activity in space and time, which may result in various undesirable effects or even toxicity. In this thesis, photopharmacology is suggested as a useful tool to achieve specific control of muscarinic acetylcholine M1 receptor (M1R) by light. Three photo-responsive compounds (i.e. FR-1, FR-2 and FR-3) derived from pirenzepine, a clinically approved and widely used M1R-selective antagonist, have been tested on HEK cells overexpressing the M1R. The illumination at different wavelengths is known to induce a conformational change in these photo-responsive compounds, resulting in their controlled activation and the subsequent activation of their targets. The calcium imaging assay results revealed that FR-1-mediated M1R photocontrol had the highest efficacy to selectively antagonize the receptor. Based on these data this photo-responsive compound was selected and tested to validate its effective antagonism in rat cortical slices through local field potential (LFP) recordings. These recordings showed a cortical activity upon photo-stimulation of FR-1, which, at least in a preliminary phase, was supported by previous calcium imaging data.