6533b829fe1ef96bd128acd2

RESEARCH PRODUCT

Optical release of caged glutamate for stimulation of neurons in the in vitro slice preparation

subject

description

Optical stimulation techniques prove useful to map func- tional inputs in the in vitro brain slice preparation: Glutamate released by a focused beam of UV light induces action potentials, which can be detected in postsynaptic neurons. The direct activation effect is influenced by factors such as compound concentration, focus depth, light absorption in the tissue, and sensitivity of different neuronal do- mains. We analyze information derived from direct stimulation ex- periments in slices from rat barrel cortex and construct a computa- tional model of a layer V pyramidal neuron that reproduces the experimental findings. The model predictions concerning the influ- ence of focus depth on input maps and action potential generation are investigated further in subsequent experiments where the focus depth of a high-numerical-aperture lens is systematically varied. With our setup flashes from a xenon light source can activate neuronal com- partments to a depth of 200 mm below the surface of the slice. The response amplitude is influenced both by tissue depth and focus plane. Specific somatodendritic structures can be targeted as the prob- ability of action potential induction falls off exponentially with dis- tance. Somata and primary apical dendrites are most sensitive to un- caged glutamate with locally increased sensitivity on proximal apical dendrites. We conclude that optical stimulation can be targeted with