Concurrent reflectance imaging and microdialysis in the freely behaving cat.
We present a method to perform simultaneous microdialysis with light reflectance imaging of neural activity in a discrete brain region of the freely behaving animal. We applied this method to the dorsal hippocampus of freely behaving cats to (1) measure extracellular glutamate and reflectance variations across a sleep-waking cycle, (2) assess spatially coherent neural activity changes accompanying local perfusion of cocaine and (3) measure local changes in cell volume induced by infusion of hyper- and hypo-osmotic solutions. Higher extracellular glutamate concentrations corresponded to higher imaged neural activity. Sequential images showed that cocaine perfusion elicited a propagating reflectance change as cocaine reached the tissue. Microperfusion of hypo-osmotic solution ( - 100 mOsm), which increases cell volume, decreased reflectance. Microperfusion of hyperosmotic sucrose solutions, which reduce cell volume, increased reflectance in a dose-dependent manner. The data indicate that reflectance imaging can measure changes in cell volume, and could, thus, measure neural activity through activity/cell volume corollaries. Combining microdialysis and optical imaging enables investigation of the neurochemical bases of spontaneous neural activity patterns within discrete brain nuclei.
Poe
G R
GR
Interdepartmental Program in Neuroscience, University of California Los Angeles School of Medicine 90095-1763, USA.
Nitz
D A
DA
Rector
D M
DM
Kristensen
M P
MP
Harper
R M
RM
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000166:cytology* / Q000502:physiology; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology*; D002415:Cats; D048429:Cell Size; D002851:Chromatography, High Pressure Liquid; D003042:Cocaine / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000295:instrumentation*; D004569:Electroencephalography; D005336:Fiber Optic Technology; D018698:Glutamic Acid / Q000378:metabolism; D017551:Microdialysis / Q000295:instrumentation / Q000379:methods*; D009294:Narcotics / Q000494:pharmacology; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D009994:Osmolar Concentration; D014743:Videotape Recording
D009294:Narcotics; D018698:Glutamic Acid; D003042:Cocaine