Fig. 6 |. Two-photon imaging of neurotransmitter or neuromodulator dynamics in different preparations and model organisms.
A | Two-photon imaging of acetylcholine (ACh) dynamics at subcellular level. Direction-selective ganglion cells of mouse retina were selectively labelled with G protein-coupled receptor (GPCR)-activation-based sensor for acetylcholine (GRABACh3.0; ACh3.0), using intravitreal injection of adeno-associated virus 9 (AAV9) expressing the sensor under control of the human synapsin promoter (hSyn) into Oxtr-T2A-Cre transgenic mice. Colours indicate preferred direction for each site on dendrites, quantified from responses to spots of light moving in eight directions. B | Imaging of endocannabinoid (eCB) dynamics with good spatiotemporal resolution. Fluorescence images of local eCB dynamics at single axonal boutons by expressing GRABeCB2.0 (eCB2.0) in cannabinoid receptor type 1-expressing (CB1R+) neurons in CA1 region of hippocampus. Scale bar, 5 μm (part Ba). Example local field potential (LFP) trace (top), Ca2+ dynamics (assessed using genetically encoded calcium indicator jRGECO1a; middle) and eCB dynamics imaged using eCB2.0 (bottom) of imaged mediolateral projections during stimulus-induced non-convulsive seizures and subsequent spreading wave. Dashed vertical line at time 0 indicates stimulus onset (part Bb). C | Imaging of odorant-evoked dopamine (DA) release in olfactory mushroom body in a live fly measured using two-photon microscopy. To express GRABDA1m (DA1m) in dopaminergic neurons, transgenic UAS-DA1m flies were crossed with tyrosine hydroxylase (TH)-GAL4 flies. The odorant elicited fluorescence increases prominently in the β′ lobes, not the β/γ lobes. Scale bar, 20 μm. Panel A adapted with permission from REF.147. Panel B adapted with permission from REF.88. Panel C adapted with permission from REF.78.