Journal of the autonomic nervous system
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The anatomical and functional organization of cardiac vagal preganglionic somata and the organization of ascending spinal pathways regulating the cell bodies were studies in the dog and cat. Horseradish peroxidase was injected subepicardially in cats after left or right cervical vagotomy to retrogradely label cardiomotor neurons. Somata were ipsilateral to the intact vagus in the dorsal motor nucleus (DMN) of the vagus, the nucleus ambiguus (NA) and an intermediate zone (IZ) between the DMN and NA. ⋯ Bilateral lesions placed in the dorsolateral sulcus area abolished the effects of somatic afferent stimulation. Thus, an ascending pathway regulating somata of the DMN and NA is located bilaterally in the dorsolateral sulcus. Similar studies in the dog suggested the pathway extends into the dorsolateral funiculus as well.
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J. Auton. Nerv. Syst. · Feb 1981
Role of baroreceptor reflexes in the hemodynamic and heart rate responses to althesin, ketamine and thiopentone anesthesia.
The effects of i.v. infusions of althesin, ketamine and thiopentone were studied in instrumental rabbits, in doses that produced similar levels of light anesthesia. The main hemodynamic differences were in the rises in mean arterial pressure (MAP) and in total peripheral resistance (TPR) which were in the order of ketamine greater than thiopentone greater than althesin. These rises in MAP and TPR did not occur in sino-aortic denervated rabbits suggesting that in normal rabbits these depended on the integrity of the arterial baroreceptors and /or chemoreceptors. ⋯ All drugs depressed the following curve parameters: (i) HP range, i.e. the difference in HP plateaux from maximal tachycardia to maximal bradycardia; and (ii) the reflex gain (sensitivity). The order of depression was ketamine greater than thiopentone greater than althesin, i.e. the same as the order in which they evoked pressor effects. The results suggest that the 3 anesthetics produce differing depression of afferent mechanisms related to baroreceptor reflexes and that this accounts for both the differences in pressor effects (through disinhibition of constrictor tone) and in depression of the vagal and sympathetic components of the baroreceptor--heart rate reflex.