The Japanese journal of physiology
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The upper airway is a vital part of the respiratory tract. Although the upper airway serves several functions, protection of the airway and preservation of airway patency are the most essential functions subserved by upper airway reflexes. Various types of nerve endings have been identified in and under the epithelium of the upper airway, and afferent nerve endings are the natural starting of all reflex activity. ⋯ Both depression and exaggeration of upper airway reflexes cause clinical problems. Depression of upper airway reflexes enhances the chance of pulmonary aspiration and compromises the maintenance of the airway, whereas exaggeration of airway reflexes such as laryngospasm and prolonged paroxysm of cough can be harmful and dangerous. In this review, various aspects of upper airway reflexes are discussed focusing on the functions of upper airway reflexes in humans and some pathophysiological problems related to clinical medicine.
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Numerous studies have demonstrated that acupuncture and moxibustion induce analgesic effects. This study examined whether diffuse noxious inhibitory controls (DNIC) participated in acupuncture and moxibustion induced-analgesia. Single unit extracellular recordings from neurons in the trigeminal nucleus caudalis of urethane-anesthetized Wistar rats were obtained with a glass micropipette. ⋯ Pinch stimulation induced the most profound suppression followed by manual acupuncture. Moxibustion induced moderate suppression with a long induction time. These results suggest that DNIC may be involved in the analgesic mechanism of acupuncture and moxibustion.
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The ventilatory response to acute systemic hypoxia has been thought to be determined by the balance between hypoxic stimulation via peripheral chemoreceptors and hypoxic inhibition of the respiratory neurons. In moderate-severe hypoxia, the latter predominates the former resulting in ventilatory "depression" (HVD). However, ventilation relative to metabolic rate (V. ⋯ The possible origin of CO2 accumulation in the venous blood, such as the buffering of lactic acid by bicarbonate, and its role in ventilatory stimulation are discussed. Since there was no large increase in V. E and metabolic rate in the post-hypoxic period, "O2 debt" during HVD was small.
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Review Comparative Study
Neuronal mechanisms of respiratory rhythm generation: an approach using in vitro preparation.
The respiratory network in the ventrolateral medulla of the brainstem-spinal cord preparation from newborn rat involves pre-inspiratory (Pre-I) neurons, three types of inspiratory (Insp I, II, III) neurons and two types of expiratory (Exp-i, Exp-p-i) neurons as major subtypes, which were classified according to patterns of postsynaptic potentials. The neuronal respiratory-related membrane potential fluctuations of these cells indicate at least four distinguishable phases of the in vitro respiratory cycle: pre-inspiratory, inspiratory, post-inspiratory (E1), and late-expiratory (E2). A current hypothesis for the central pattern generator of respiration proposed by our group is that Pre-I neurons in the rostral ventrolateral medulla, with intrinsic burster properties, produce the primary respiration rhythm. ⋯ Respiratory neuron networks in this preparation were compared with those of different in vitro preparations, like rhythmic slices or perfused brainstems and of adult mammals in vivo. Many types of synaptic connections among respiratory neurons in adult mammals were also found in the (rostral) ventrolateral medulla of a brainstem-spinal cord preparation from newborn rat. The characteristics of the inspiratory burst pattern and inspiratory off switch mechanisms in newborn rat preparations might be explained by insufficient inhibitory (or excitatory) synaptic inputs to the inspiratory pattern generator due to an immature neuron network and/or deafferentiation.
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Nociceptive thalamic units receiving afferent input from the greater splanchnic nerve (SPL) were recorded from the nucleus ventralis posterolatealis (VPL) and intralaminar nuclei in urethane-chloralose anesthetized cats. The effects of stimulating the periaqueductal gray (PAG), or the nucleus raphe dorsalis (NRD) on responses of nociceptive thalamic units were investigated. Forty-eight nociceptive specific (NS) and 20 wide dynamic range (WDR) units with SPL input were found in the shell region of the caudal VPL. ⋯ Of 113 intralaminar nociceptive units studied, 68 units were unaffected, 23 units were excited and 22 units were inhibited following the conditioning stimulation. In the units in which responses to SPL stimulation were inhibited, responses elicited by electrical stimulation of the mesencephalic reticular formation (MRF) were also inhibited. These data suggest that although there is an ascending inhibitory pathway from PAG/NRD to intralaminar nuclei, this system is far less potent compared with the ascending inhibitory system acting upon the VPL.