Relative mitochondrial membrane potential and [Ca2+]i in type I cells isolated from the rabbit carotid body.

1. In the accompanying paper (Duchen & Biscoe, 1992) we have described graded changes in autofluorescence derived from mitochondrial NAD(P)H in type I cells of the carotid body in response to changes of PO2 over a physiologically significant range. These observations suggest that mitochondrial function in these cells is unusually sensitive to oxygen and could play a role in oxygen sensing.

Mitochondrial function in type I cells isolated from rabbit arterial chemoreceptors.

1. In this, and the accompanying paper (Duchen & Biscoe, 1992), we test the hypothesis that the oxygen sensitivity of mitochondrial electron transport forms a basis for transduction in the carotid body, the primary peripheral arterial oxygen sensor. We here describe for isolated type I cells the changes in autofluorescence of mitochondrial NAD(P)H that accompany changes in PO2.

Responses of type I cells dissociated from the rabbit carotid body to hypoxia.

1. The carotid body chemoreceptors are stimulated in situ by hypoxia. We have studied type I cells freshly dissociated from the carotid body of the rabbit.

Cellular basis of transduction in carotid chemoreceptors.

Understanding transduction mechanisms is central to much of sensory physiology. The carotid chemoreceptors monitor the PO2 of arterial blood en route to the brain and are powerfully excited when the arterial PO2 falls to less than 60 mmHg. The type I cell is generally believed to be the transducer.

Measurements of intracellular Ca2+ in dissociated type I cells of the rabbit carotid body.

1. The carotid body chemoreceptors are stimulated in situ by cyanide (CN-), which mimics the effect of hypoxia. We have shown that CN- increases a calcium-dependent potassium conductance (gK(Ca)) in single type I cells dissociated from the carotid body of the rabbit.

Electrophysiological responses of dissociated type I cells of the rabbit carotid body to cyanide.

1. The carotid body is the major peripheral sensor of arterial PO2 in the mammal and is excited by cyanide (CN-). Type I cells, the presumed sites for transduction, were freshly dissociated from the carotid body of the adult rabbit and studied with the whole-cell patch clamp technique.

Biophysical studies of the cellular elements of the rabbit carotid body.

The carotid body is a major sensor of oxygen partial pressure in the arterial blood, and plays a role in the control of respiration. Despite extensive investigation of the structure, the cellular basis of the transduction mechanism remains poorly understood. We have developed a preparation of freshly dissociated cells from the rabbit carotid body, in which two cell types may be identified using morphological criteria.

Primary afferent terminal excitability in the normal and spastic mutant mouse spinal cord.

A microcomputer-based system has been used to apply the technique of excitability testing to the study of the actions of a range of pharmacological agents on the excitability of single primary afferent terminals in the mouse spinal cord in vitro. GABAA analogues all evoked increases in excitability that were bicuculline sensitive. GABA itself also evoked biphasic changes in excitability, or occasionally only suppressed terminal excitability.

Synaptic physiology of spinal motoneurones of normal and spastic mice: an in vitro study.

Spinal cord reflexes have been examined in a preparation of the mouse spinal cord maintained in vitro. Responses of the motoneurone population of normal and spastic mutant mice to stimulation of a segmental dorsal root were compared. In the normal spinal cord, a monosynaptic response with very little polysynaptic excitation was typical.

An intracellular study of the interactions of N-methyl-DL-aspartate with ketamine in the mouse hippocampal slice.

Intracellular recordings were made from dentate and CA1 pyramidal cells of the mouse hippocampal slice preparation. N-methyl-DL-aspartate (NMDLA), quisqualate and kainate and the anaesthetic agent, ketamine, were applied by microelectrophoresis. Excitation by NMDLA but not by the other amino acids, was associated with increased outward rectification.

Actions and interactions of GABA and benzodiazepines in the mouse hippocampal slice.

Intracellular recordings have been made from CA1, CA3 and dentate cells of the mouse hippocampal slice. Gamma-aminobutyric acid (GABA) and the water-soluble benzodiazepines, midazolam and flurazepam were applied close to the impaled cell somata by microelectrophoresis. GABA always caused a fall in input resistance, although the associated changes in membrane potential were variable.

The anion selectivity of GABA-mediated post-synaptic potentials in mouse hippocampal cells.

Intracellular recordings were made from CA1 and dentate cells of the mouse hippocampal slice. When potassium acetate was used to fill the electrodes, spontaneous synaptic activity was rarely seen in CA1 or dentate cells. In contrast, when electrodes filled with potassium chloride were used, spontaneous depolarizing post-synaptic potentials (p.

An intracellular study of dentate, CA1 and CA3 neurones in the mouse hippocampal slice.

Intracellular recordings were made from CA1 and CA3 pyramidal cells and from dentate granule cells of the mouse hippocampal slice preparation. The passive electrical properties of the cells and their responses to electrical stimulation of the major antidromic and orthodromic pathways were explored. The majority of cells were impaled between 60 and 100 micron from the surface of the slice.

On the location of gamma-aminobutyrate and benzodiazepine receptors in the cerebellum of the normal C3H and Lurcher mutant mouse.

Binding of gamma-aminobutyrate and benzodiazepine receptor ligands has been studied in the cerebellum of adult normal (C3H) and Lurcher mutant mice. The adult mutant has lost all Purkinje cells and more than 90% of the granule cells in the cerebellar cortex. When compared with their normal littermates Lurcher mice displayed large decreases in the number of high-affinity binding sites for [3H]muscimol, a synaptic gamma-aminobutyrate receptor ligand, in washed cerebellar homogenates.

Changes in benzodiazepine receptor binding as seen autoradiographically in the central nervous system of the spastic mouse.

Quantitative light-microscope autoradiography has been used to compare the specific, clonazepam-displaceable binding of [3H]flunitrazepam, a photoaffinity label for the 1,4-benzodiazepine receptor, in different regions of the brain and spinal cord of spastic mice and their unaffected littermates. Specific binding of [3H]flunitrazepam in the central nervous system of the spastic mouse showed significant increases in the anterior colliculus and pretectal area and in all laminae of the grey matter in the lumbar spinal cord. These results confirm homogenate binding assays suggesting an increased number of benzodiazepine receptors in the spinal cord of the spastic mouse.

Autoradiography of benzodiazepine receptor binding in the central nervous system of the normal C57BL6J mouse.

[3H]flunitrazepam has been used as a photoaffinity label for the specific, clonazepam-displaceable 1,4-benzodiazepine binding sites in sections of normal C57BL6J mouse brain and spinal cord. Binding was visualized by light microscope autoradiography and quantified by a simple microdensitometric procedure. Specific flunitrazepam binding was seen to be highest in the colliculi, cerebral cortex, hippocampal formation, interpeduncular nucleus, mamillary body, hypothalamus, olfactory tubercle, and in the molecular layer and deep nuclei of the cerebellum.

The carotid body chemoreceptor: an investigation in the mouse.

The carotid body chemoreceptor has been investigated in the normal mouse and in the wobbler mutant. Electron microscopic studies show that the synaptic vesicle-containing nerve endings on type I cells are reduced in number in the mutant to 4.2% of the normal number.

Quantitative light and electron microscopic studies on the ventral roots of the wobbler mutant mouse.

In wobbler mutant mice and normal litter-mates the numbers of axons have been counted in cervical and lumbar ventral roots and the dimensions of nerve fibres measured in the fifth cervical, C5, and third lumbar, L3, roots. In wobbler cervical ventral roots C5, C7 and C8 and lumbar roots L4 and L5 the number of axons was reduced. Abnormal features were seen in all mutant cervical ventral roots but not in the lumbar roots.

Numbers and sizes of nerve fibres in mouse spinal roots.

The numbers of myelinated and non-myelinated nerve fibres in the spinal roots of one strain of mouse have been counted from electron micrographs and the accuracy of counting procedures assessed. Non-myelinated nerve fibres are present in the ventral roots at all levels though the largest number are found inthe thoracic and L1, L5, L6 and S1 ventral roots. The number is very small in L2, L3, and L4 ventral roots which are those supplying the hind limb.

Some pharmacological studies on the spastic mouse.

1 Full-wave rectification and integration of the EMG signal recorded from the hamstring muscles of the spastic mouse was used to evaluate the actions of a variety of drugs on the muscle rigidity of these mutants, animals in which no histological lesion has yet been found. 2 Profound and long-lasting muscle relaxant responses were consistently observed upon the injection of diazepam (2 mg/kg, i.p.

The sizes of motoneurons supplying hindlimb muscles in the mouse.

Motoneurons supplying identified muscle groups in the mouse spinal cord were labelled by retrograde transport of horseradish peroxidase. The size of motoneurons was estimated by measuring perimeter and cross-sectional area at the level of the nucleolus for the following seven major muscle groups: quadriceps femoris, adductors and gracilis, gluteal musculature, hamstring muscles, posterior crural musculature, anterolateral crural musculature and intrinsic musculature of the foot. The qualitative observation of two size ranges of motoneuron was supported by the measurements.