title: Simultaneous measurements of glucose, oxyhemoglobin and deoxyhemoglobin in exposed rat cortex.
abstract: The present work addresses the simultaneous monitoring of hemoglobin and glucose consumption in rat somatosensory cortex in vivo. We propose a method which combines two techniques: 2-dimensional optical imaging and an amperometric microbiosensor. The mounted setup optimizes the space in the cranial window so that three micro-electrodes can be inserted: glucose microbiosensor, sentinel and stimulating electrode as well as the holder to manipulate the optical fiber. Additionally, a tool based on graphical user interface programming has been developed to visualize a two-dimension spectral map of oxy-, deoxy- and total hemoglobin, HbO₂, HbR and HbT respectively, in the cortex. Our results showed a good sensitivity, selectivity and spatial resolution for both methods. Relevant hemodynamic responses had a common central focus (at the site of the stimulus) which later segregated to other vascular compartments. A good linear relationship between extracellular glucose concentration and HbO₂ values during brain activation after local electrical stimulation was observed for electrochemical and optical recordings (R² values were over 0.94). Time courses between glucose and HbO₂ signals showed a temporal delay ranging from 1 s to 2 s, suggesting that both variables are not always coupled. The temporal mismatching reported here, provides in vivo evidence that supports a neuronal hypothesis: cerebral blow flow and oxidative metabolism are driven in parallel by neural activity--rather than a concatenation of events ('in-series' events) occurring at sites of neuronal activation.
authors.affiliation: Neurochemistry and Neuroimaging Group, Faculty of Medicine, University of La Laguna, Campus de Ofra s/n, 38071 Tenerife, Spain. rossanyroche@gmail.com
authors.forename: R
authors.initials: R
authors.lastname: Roche
authors.forename: P
authors.initials: P
authors.lastname: Salazar
authors.forename: M
authors.initials: M
authors.lastname: Martín
authors.forename: F
authors.initials: F
authors.lastname: Marcano
authors.forename: J L
authors.initials: JL
authors.lastname: González-Mora
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002540:Cerebral Cortex / Q000098:blood supply / Q000378:metabolism* / Q000601:surgery; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D005947:Glucose / Q000032:analysis / Q000378:metabolism*; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism*; D008297:Male; D010108:Oxyhemoglobins / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D056969:Voltage-Sensitive Dye Imaging / Q000295:instrumentation / Q000379:methods*
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D005947:Glucose