Project Summary
Pharmacological probes are widely used to study the nervous system. Despite often exhibiting exquisite
specificity for target receptors, due to diffusion, traditional small molecule drugs act slowly and with spatial
imprecision. This impedes neuropharmacological studies in vivo, particularly those involving high resolution
electrophysiological, imaging, and behavioral tracking methods. Such studies greatly benefit from the ability to
correlate measurements with well defined, time-locked stimuli that can be readily varied in intensity and
duration. To meet this need, we are developing “caged” drugs that can be applied systemically in an inactive
form and subsequently released in the brain with high spatial and temporal precision using short light flashes.
To enable compatibility with optical measurements of neural function involving fluorescent probes, we will
develop new photochemical protecting groups that are wavelength tuned to be spectrally orthogonal to
common green and red fluorophores, in terms of both one-photon and two-photon excitation. We will further
optimize these “caging” groups to facilitate brain penetrance of the resulting caged drugs. We will evaluate the
utility of new caging groups by incorporating them into 2nd generation caged opioid drugs that should provide
significant experimental advantages over our 1st generation variants, which could only be photoactivated with
ultraviolet light. We will rigorously validate new caged opioid drugs using in vitro, ex vivo, and in vivo
experimental paradigms, culminating in behavioral assays and fiber photometry recordings of opioid-evoked
neurochemical signaling. In addition, we will develop caged ketamine derivatives that can be used to study the
neural mechanisms underlying dissociative states, as well as ketamine’s rapid antidepressant actions. Caged
ketamine variants will also be evaluated using in vitro, ex vivo, and in vivo experimental paradigms, including
measurements of spinogenesis and neural activity in the prefrontal cortex. These efforts will involve
development of an optical configuration for simultaneous two photon imaging and one photon photolysis
through implanted prisms. To maximize end-user uptake, performance criteria for both caged drug families are
determined through extensive consultation with the scientific community.
