Title

Microfiber reflection spectrophotometry of cytochrome oxidase in the rat cerebral cortex: Relationships between brain oxidative metabolism and function following direct cortical stimulation

Date of Award

1988

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physiology and Biophysics

First Committee Member

Myron Rosenthal, Committee Chair

Abstract

Laminar profiles of response to surface direct cortical and thalamic ventrobasal (VB) stimulation were recorded in pentobarbitol-anesthetized rat cerebral cortex in situ. Data were collected by reflection spectrophotometry of cytochrome oxidase (cytochrome a,a$\sb3$) using a microfiber light collector developed for this dissertation, and by microelectrodes sensitive to (K$\sp+$)o and tissue oxygen tension.Comparisons of the microfiber reflection spectrophotometer with macroreflection spectrophotometers currently in use, indicated that this new system can detect redox changes of cytochrome a,a$\sb3$ from tissue approximately 50 um by 100 um in size and from subsurface areas. This is a significant advance over earlier optical techniques.Direct cortical stimulation was accompanied by transient (K$\sp+$)o increases which decreased in amplitude with distance from the surface except in lamina IV. These increases were greater than those recorded in adjacent lamina but were not as large as those recorded close to the stimulus. Stimulation was also accompanied by transient oxidation of cytochrome a,a$\sb3$. The magnitude of these oxidative responses increased with depth to a maximum in lamina IV and then decreased with increasing depth. From the surface to lamina IV, PtO$\sb2$ transiently decreased or was unchanged by stimulation. At lamina IV, PtO$\sb2$ was unchanged or was biphasically decreased and then increased. Beyond this depth, PtO$\sb2$ consistently increased with stimulation.Thalamic VB nucleus stimulation was accompanied by transient (K$\sp+$)o increases which increased in amplitude with distance from the surface to a peak in lamina IV, and decreased with increasing depths. Stimulation was again accompanied by transient oxidation of cytochrome a,a$\sb3$ which increased with depth to a maximum in lamina IV and then decreased with increasing depth. From the surface to lamina IV, PtO$\sb2$ transiently increased or was unchanged by stimulation. At lamina IV, PtO$\sb2$ was unchanged or was biphasically decreased and then increased. Beyond this depth, PtO$\sb2$ consistently increased or was unchanged by stimulation.These data demonstrate that the intensity of local cerebral oxidative metabolic activity may not be determined solely by the potassium load at each lamina and may indicate that recovery metabolism following direct cortical stimulation is maximum at lamina IV.

Keywords

Biology, Neuroscience

Link to Full Text

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