Journal of the autonomic nervous system
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J. Auton. Nerv. Syst. · Apr 1981
Organization of the sacral parasympathetic reflex pathways to the urinary bladder and large intestine.
Electrophysiological and horseradish peroxidase (HRP) techniques have provided new insights into the organization of the sacral parasympathetic reflex pathways to the large intestine and urinary bladder. The innervation of the two organs arises from separate groups of sacral preganglionic cells: (1) a dorsal band of cells in laminae V and VI providing an input to the intestine; and (2) a lateral band of cells in lamina VII providing an input to the bladder. These two groups of cells were separated by an interband region containing tract cells and interneurons. ⋯ The long latency is attributable to the slow conduction velocity in immature unmyelinated peripheral and central axons. In chronic spinal kittens (3-7 days after spinalization) the long latency reflex was abolished and a shorter latency (90-150 msec) bladder reflex was unmasked. The emergence of this spinal pathway may reflect axonal sprouting and the formation of new reflex connections within the sacral parasympathetic nucleus.
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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.