Chemoreception in the Carotid Body

It is becoming traditional that periodically those of us interested in the carotid body hold an international meeting to discuss their results. In 1966 a meeting was organized by R. W. Torrance in Oxford and in 1973 by M. J. Purves in Bristol; in 1974 A. S. Paintal organized a satellite symposium of the Physiological Congress in Kashmir. The organizers of these meetings are to be commended for their efforts in publishing both the papers and discussions. At these meetings it has become apparent that the direction of research is becoming more sharpely focused on the cellular mechanisms of chemoreception. During the meeting in Dortmund the papers dealt mostly with the different cell types in the carotid body and their environment, i. e. , local P0 and local flow. These included 2 light and electron microscopic studies of the morphometric and histochemical pro­ perties of the different cells, microelectrode studies of the glomoid tissue to understand the conversion of a chemical stimulation into nervous activity, as well as strictly bio­ chemical and physiologic investigations concerning the dependence of the chemo­ receptive process on O consumption and the turnover of catecholamines. In spite 2 of the variety in methodology, it was apparent that all contributors had a common interest: to understand the mechanisms of chemoreception. Although at the meeting itself there was ample time to fully discuss the various papers, it has become necessary here to shorten the papers and discussions; otherwise the cost of publication would have been prohibitive.

Session I: Morphometric and Histologic Analysis of the Cell Elements in the Carotid Body Tissue.- Light-Microscopic and Electron-Microscopic Studies on the Morphology of Cat Carotid Body.- Origin of Nerve Terminals on Glomus Cells in Cat Carotid Body: A Study of Axoplasmic Movement of Labeled Material Along Sensory Neurons of the Petrosal Ganglion.- Identification of Sensory Axon Terminations in the Carotid Body by Autoradiography.- Degenerative Changes in Rabbit Carotid Body Following Systematic Denervation and Preliminary Results about the Morphology of Sinus Nerve Neuromas.- Regeneration of Nerves and Nerve Terminals in Rabbit Carotid Body Following Carotid Nerve Sectioning and Suturing.- Chemoreceptor Activity in the Rabbit Carotid Sinus Nerve During Regeneration.- Recovery of Chemosensory Function of Regenerating Carotid Nerve Fibers.- Studies of Normal and Wobbler Mutant Carotid Bodies.- Fine Structure of Pressoreceptor Terminals in the Carotid Body (Mouse, Cat, Rat).- Capillary Distances and Oxygen Supply to the Specific Tissue of the Carotid Body.- Session II: Electrophysiological Characteristics of the Cell Elements in the Carotid Body.- Effects of Temperature and Stimulating Agents on Carotid Body Cells.- Are the Conventional Electrophysiological Criteria Sufficient to Give Evidence of an Electrogenic Sodium Transport Across Neuronal Membranes?.- Reaction of Cultured Carotid Body Cells to Different Concentrations of Oxygen and Carbon Dioxide.- Meaning of the Type I Cell for the Chemoreceptive Process - An Electrophysiological Study on Cultured Type I Cells of the Carotid Body.- Session III: Histochemical and Biochemical Investigation of the Transmitters in the Carotid Body.- Dopamine Beta-Hydroxylase Activity in the Cat Carotid Body.- Endogenous Acetylcholine Levels in Cat Carotid Body and the Autoradiographic Localization of a High Affinity Component of Choline Uptake.- Molecular Biology of Chemoreceptor Function: Induction of Tyrosine Hydroxylase in the Rat Carotid Body Elicited by Hypoxia.- Effects of Hypoxia on Carotid Body Type I Cells and Their Catecholamines. A Biochemical and Morphologic Study.- Loss of Histochemically Demonstrable Catecholamines in the Glomus Cells of the Carotid Body After a-Methylparatyrosine Treatment.- Enzymes and Inhibitors of the Catecholamine Metabolism in the Cat Carotid Body.- Session IV: The Afferent and Efferent Chemoreceptive Pathway of the Carotid Body.- A Pharmacologic Study on a Possible Inhibitory Role of Dopamine in the Cat Carotid Body Chemoreceptor.- Blockade of Carotid Body Chemosensory Inhibition.- Variable Influences of the Sympathetic Nervous System Upon Carotid Body Chemoreceptor Activity.- Mechanism of Inhibition of Chemoreceptor Activity by Sinus Nerve Efferents.- Further Studies on the Fluctuation of Chemoreceptor Discharge in the Cat.- Carotid Body Chemoreceptor Afferent Neurons in the Solitary Tract Nucleus Area of the Cat.- Multifactor Influences on the Functional Relationship Between Ventilation and Arterial Oxygen Pressure.- Session V: Morphometric Analysis of Ultrastructural Changes in the Carotid Body Tissue.- Histofluorescent and Ultrastructural Studies on the Effects of Reserpine and Calcium on Dense-Cored Vesicles in Glomus Cells of the Rat Carotid Body.- Ultrastructural Changes in Sensory Nerve Endings Accompanying Increased Chemoreceptor Activity: A Morphometric Study of the Rat Carotid Body.- Dense-Cored Vesicles and Cell Types in the Rabbit Carotid Body.- The Carotid Body Chief Cell as a Paraneuron.- Session VI: Environmental Conditions for the Chemoreceptive Process in the Carotid Body.- Factors Affecting O2 Consumption of the Cat Carotid Body.- Mathematical Analysis of Oxygen Partial Pressure Distribution of the Carotid Body Tissue.- Comparative Measurements of Tissue PO2 in the Carotid Body.- A Functional Estimate of the Local PO2 at Aortic Chemoreceptors.- Role of Calcium Ions in the Mechanism of Arterial Chemoreceptor Excitation.- Tissue P02 in the Cat Carotid Body During Respiratory Arrest After Breathing Pure Oxygen.- Relationship Between Local Flow, Tissue P02, and Total Flow of the Cat Carotid Body.- Effects of Temperature on Steady-State Activity and Dynamic Responses of Carotid Baroand Chemoreceptors.- Manipulation of Bicarbonate in the Carotid Body.