Reversible silencing of endogenous receptors in intact brain tissue using 2-photon pharmacology

Abstract

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

Adrenergic Modulation With Photochromic Ligands

“…These results enable multiple applications that were previously unaccessible for adrenergic neurotransmission and open the way to achieve optimized photopharmacological properties based on this scaffold. On‐demand modulation at specific locations might allow to single out adrenergic projections from the LC and to dissect their function in circuits and behaviour with high resolution [50, 51] . Moreover, adrenoswitches can enable photocontrol over a variety of physiological functions, like pupillary responses, and help unravel their physiology in vivo.…”

Adrenergic Modulation with Photochromic Ligands

“…On-demand modulation at specific locations might allow to single out adrenergic projections from the LC and to dissect their function in circuits and behaviour with high resolution. [50,51] Moreover,a drenoswitches can enable photocontrol over av ariety of physiological functions,l ike pupillary responses,and help unravel their physiology in vivo.…”

Control of brain state transitions with light

“…In particular, two-photon stimulation of PAI using pulsed infrared light 23 offers the promise of subcellular resolution in three dimensions, as recently demonstrated with endogenous mGlu 5 . 65 Compared to the local and often inhomogeneous expression patterns achieved with viral injections of optogenetic constructs, diffusible small molecules like PAI can be in principle applied to larger brain regions to control neuronal oscillations. 57 Thus, remote control of brain waves based on the photopharmacological manipulation of endogenous muscarinic receptors may reveal the complex 3D molecular signalling underlying brain states and their transitions, in order to link them with cognition and behavior in a diversity of wildtype organisms.…”