Time-resolved laser spectroscopy of brain tissue in freely moving rodents: an opportunity to assess energy metabolism during behavioural activity
N. Mathevon 1,2, S. Mottin2, P. Laporte2 and R. Cespuglio3
1Lab.
de Biologie Animale et Appliquée, Université Jean Monnet, St-Etienne, France
2Lab. de Traitement du Signal et Instrumentation , CNRS UMR 5516,
St-Etienne, France
3Lab. de Neurobiologie des Etats de Sommeil et de Rêve, INSERM
U480, Lyon, France
We present a method allowing potential identification and following of any fluorescent compound in all brain tissue (cortex or deep nuclei) of unanaesthetized freely moving animals, with a good spatial resolution. By time-resolved spectroscopy and a UV-visible kHz femtosecond laser, and using optical properties of NADH and oxidised flavins, we are able to perform rapid assessment of the metabolic changes occurring within defined brain regions. The temporal resolution is 10 seconds. The measures can potentially be performed for several hours to weeks within a single individual.
We analyse spectrotemporal parameters of autofluorescence at different excitation wavelengths. This allows measurements of metabolic activity by means of intramitochondrial NADH (excitation wavelengths: 337 and 355 nm) and flavins (excitation wavelength: 415 nm). Moreover, using the 480 nm excitation wavelength, we investigate autofluorescence in the range of Green Fluorescent Protein (E-GFP) absorption. Our method may then allow the following of a reporter gene activity.
Allowing to work with freely moving animals and providing real time measures, this method leads the way for real-time recordings of brain metabolism variations and genic activity concomitantly with the assessment of other physiological parameters (EEG, EMG, etc.) and behavior.
Poster presented at Measuring Behavior 2000, 3rd International Conference on Methods and Techniques in Behavioral Research, 15-18 August 2000, Nijmegen, The Netherlands