Profiles of percent reduction of cytochromes in guinea pig hippocampal brain slices in vitro

Metabolism of the dorsal cochlear nucleus in rat brain slices

In vitro brain slices of the cochlear nucleus have been used for electrophysiological and pharmacological studies. More information is needed about the extent to which the slice resembles in vivo tissue, since this affects the interpretation of results obtained from slices. In this study, some chemical parameters of the dorsal cochlear nucleus (DCN) in rat brain slices were measured and compared to the in vivo state. The activities of malate dehydrogenase and lactate dehydrogenase were reduced in some DCN layers of incubated slices compared to in vivo brain tissue. The activities of choline acetyltransferase and acetylcholinesterase were increased or unchanged in DCN layers of slices. Adenosine triphosphate (ATP) concentrations for in vivo rat DCN were similar to those of cerebellar cortex. Compared with in vivo values, ATP concentrations were decreased in the DCN of brain slices, especially in the deep layer. Vibratome-cut slices had lower ATP levels than chopper-cut slices. Compared with the in vivo data, there were large losses of aspartate, glutamate, glutamine, gamma-aminobutyrate and taurine from incubated slices. These amino acid changes within the slices correlated with the patterns of release from the slices.

Use of voltage-sensitive dyes and optical recordings in the central nervous system

Understanding the spatio-temporal features of the information processing occurring in any complex neural structure requires the monitoring and analysis of the activity in populations of neurons. Electrophysiological and other mapping techniques have provided important insights into the function of neural circuits and neural populations in many systems. However, there remain limitations with these approaches. Therefore, complementary techniques which permit the monitoring of the spatio-temporal activity in neuronal populations are of continued interest. One promising approach to monitor the electrical activity in populations of neurons or on multiple sites of a single neuron is with voltage-sensitive dyes coupled with optical recording techniques. This review concentrates on the use of voltage-sensitive dyes and optical imaging as tools to study the activity in neuronal populations in the central nervous system. Focusing on 'fast' voltage-sensitive dyes first, several technical issues and developments in optical imaging will be reviewed. These will include more recent developments in voltage-sensitive dyes as well as newer developments in optical recording technology. Second, studies using voltage-sensitive dyes to investigate information processing questions in the central nervous system and in the invertebrate nervous system will be reviewed. Some emphasis will be placed on the cerebellum, but the major goal is to survey how voltage-sensitive dyes and optical recordings have been utilized in the central nervous system. The review will include optical studies on the visual, auditory, olfactory, somatosensory, auditory, hippocampal and brainstem systems, as well as single cell studies addressing information processing questions. Discussion of the intrinsic optical signals is also included. The review attempts to show how voltage-sensitive dyes and optical recordings can be used to obtain high spatial and temporal resolution monitoring of neuronal activity.

Mapping patterns of neuronal activity and seizure propagation by imaging intrinsic optical signals in the isolated whole brain of the guinea-pig

Image analysis techniques were used to examine changes in the intrinsic optical properties in the isolated brain of the guinea-pig in order to map normal neuronal activity patterns and seizure propagation in the olfactory cortex. Electrical stimulation of the lateral olfactory tract decreased light reflectance in distant cortical areas where fibres of the tract are known to project. These areas included the amygdalar, anterior and posterior piriform, and entorhinal cortices, as well as the olfactory tubercle. Stimulation of the lateral entorhinal cortex decreased reflectance in a more circumscribed area in the lateral and medial entorhinal cortex. By imaging intrinsic signals in real-time, we also demonstrated that seizure activity elicited in the entorhinal cortex/hippocampus preferentially propagated to the posteromedial cortical amygdaloid nucleus. The magnitudes of the intrinsic optical signals were correlated with the amplitudes of field potentials recorded in laminae II or III of the olfactory cortex of the same preparations. These signals had onset times of approximately 3 s during 5 Hz stimulation, consistently recovered and were graded with stimulation frequency. The generation of the intrinsic signals required postsynaptic activation, since attenuating synaptic transmission with kynurenic acid (an excitatory amino acid antagonist) eliminated the signals. The intrinsic signals exhibited maxima at 425-450, 550 and 600 nm, suggesting that they arose from changes in light absorption by cytochromes. Intrinsic signals of relatively constant magnitude were also present at 400, 475-500 and 575 nm, and at wavelengths greater than 600 nm. This suggested that an additional component of the intrinsic signal arose from changes in light scattering, possibly due to cellular swelling.

Analysis of Fungal Pellets by UV-Visible Spectrum Diffuse Reflectance Spectroscopy

The application of the UV-visible spectrum diffuse reflectance spectroscopy for the determination of intracellular pH in vivo, for determination of cytochrome content, and for the noninvasive in vivo detection of the redox state of fungal mitochondrial cytochromes in filamentous fungi is introduced. The time course of the intracellular pH values, mitochondrial cytochromes, and CO-binding pigments content and the correlations between the actual redox state of cytochrome aa 3 and saturation of growth medium with oxygen in pellets of the basidiomycete Phanerochaete chrysosporium were determined. As the test microorganism, the yeast Saccharomyces cerevisiae was used. UV-visible spectrum diffuse reflectance spectroscopy proved to be a promising method for the quick and simple analysis of light-impermeable biological structures for which the classical transmittance spectrophotometric methods are difficult to implement.

4-Aminopyridine causes reduction of cytochromes partly originated in glia with enhanced evoked potentials in the olfactory cortex slice

Enhanced electrical and metabolic activities with addition of 4-aminopyridine (4-AP) were investigated in the olfactory cortex slice by recording evoked potentials, the redox state of cytochromes and the rate of oxygen uptake. During perfusion with 4-AP (0.01-0.1 mM), the late N-wave was dose-relatedly elicited in the evoked potential, concomitant with reduction of cytochromes and acceleration of oxygen uptake. These enhanced responses by 4-AP (0.1 mM) depended on the extracellular Ca2+. When the slice was subject to 2-deoxy-D-glucose (2-DG) (10 mM), initiation of the late N-wave by 4-AP (0.1 mM) was delayed, and both the reduction of cytochromes and the raised oxygen uptake prompted by the same dose of 4-AP were also significantly attenuated. Nevertheless, the presynaptic potential and N-wave, which markedly diminished by 2-DG, became tolerant to glycopenia after addition of 4-AP. By prior exposure to fluoroacetate (1 mM), the N-wave was gradually increased, but the late N-wave was rapidly decreased in amplitude by adding 4-AP (0.1 mM). The cytochrome reduction and the accelerated oxygen uptake by 4-AP (0.1 mM) were suppressed in the presence of fluoroacetate (1 mM). These results indicate that cytochromes become reduced by 4-AP, concomitant with the enhanced evoked potentials and oxygen uptake in a Ca(2+)-dependent manner, and that glial cells probably contribute to the enhanced electrical and metabolic activities in the olfactory cortex slice.

A method for simultaneous recording of electrical activities and spectrophotometric signals from brain slice preparations in vitro

Organ spectrophotometry has been applied to analyze cytochrome redox changes in brain slice preparations. An interface-chamber method for maintaining metabolism of brain slice tissues was devised to reduce noise on recording traces of spectrophotometric signals, and then used for continuous monitoring and simultaneous recording of electrical and optical signals from brain slices. With this method, the noise level during the recording of redox states of cytochromes was decreased to 0.0004 A unit.