Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of selective opioid receptor agonists and antagonists on neural discharge recorded from carotid body arterial chemoreceptors in vivo were studied in anaesthetized cats. Mean ID50 values were determined for each agonist and used to assess chemodepressant potency on intracarotid (i.c.) injection in animals artificially ventilated with air. [Met]enkephalin, [Leu]enkephalin, [D-Ala2, D-Leu5]enkephalin and [D-Pen2, D-Pen5]enkephalin were more potent chemodepressants than [D-Ala2, Me-Phe4, Gly-ol5]enkephalin, dynorphin (1-8) or ethylketocyclazocine; morphiceptin (mu-agonist) was inactive. The rank order of potency was compatible with the involvement of delta-opioid receptors in opioid-induced depression of chemosensory discharge. ICI 154129, a delta-opioid receptor antagonist, was used in fairly high doses and caused reversible dose-related antagonism of chemodepression induced by [Met]enkephalin. It also antagonized depression caused by single doses of [Leu]enkephalin, [D-Ala2, D-Leu5]enkephalin, [D-Ala2, Me-Phe4, Gly-ol5]enkephalin or dynorphin (1-8). ICI 174864, a more potent and selective delta-opioid receptor antagonist, also antagonized chemodepression induced by [Met]enkephalin or by the selective delta-receptor agonist [D-Pen2, D-Pen5]enkephalin. Comparison of background or 'spontaneous' chemosensory discharge during the 30 min periods immediately before and after injecting ICI 174864 (0.1-0.2 mg kg-1 i.c.) showed a significant increase in discharge in one experiment, but in four others discharge was either unaffected or decreased after the antagonist, which argues against a toxic depression of chemosensors by endogenous opioids under resting conditions in our preparation. Sensitivity of the carotid chemoreceptors to hypoxia (ventilating with 10% O2) was increased significantly after ICI 174864, which could be taken as evidence that endogenous opioids depress chemosensitivity during hypoxia. In contrast, responsiveness to hypercapnia was reduced after the antagonist, implying that endogenous opioids may potentiate chemoreceptor sensitivity during hypercapnia. The results obtained using 'selective' agonists and antagonists provide evidence that depression of chemosensory discharge caused by injected opioids involves a delta type of opioid receptor within the cat carotid body. Endogenous opioids may modulate arterial chemoreceptor sensitivity to physiological stimuli such as hypoxia and hypercapnia.
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PMID:Characterization of opioid receptors in the cat carotid body involved in chemosensory depression in vivo. 287 62

The dispersed neuroendocrine (NE) system is represented in the bronchopulmonary tract by the solitary neuroendocrine cells and the neuroepithelial bodies (NEBs). Immunohistochemically, neuron-specific enolase, serotonin, bombesin, and calcitonin are demonstrable in both components, whereas leu-enkephalin is demonstrable only in solitary NE cells. The precise function of and interplay between these two components under physiologic and pathologic conditions are not entirely clear. Current indications are that NEBs act as intrapulmonary chemoreceptors sensitive to hypoxia and hypercapnia, whereas solitary NE cells may have a paracrine, regulatory function. Even less clear is the possible role of solitary NE cells and NEBs in the processes associated with intrauterine and neonatal pulmonary growth and maturation. Various experimental manipulations have resulted in proliferation of solitary NE cells and NEBs. Of particular interest is the apparently selective proliferative effect on NEBs shown by several nitroso compounds. Diethylnitrosamine administration to hamsters for several weeks results in an increase in the number of NEBs and an increase in the number of cells per NEB. These hyperplastic NEBs express the same immunoreactive hormones as their normal counterparts. However, when NEB cells from diethylnitrosamine-treated hamsters are cultured in vitro a notable proportion of the resulting endocrine cells express ACTH immunoreactivity. Interestingly, the neoplasms that eventually develop in these hamsters are not comprised of NE cells. Studies on human bronchi from specimens resected for various types of neoplasms and for bronchiectasis with and without associated chronic obstructive pulmonary disease have revealed frequent hyperplasias of solitary NE cells and NEBs. In about 10% of the specimens, dysplastic aggregates of solitary NE cells and NEBs are found. Unexpected "microcarcinoids" and tumorlets are also seen. The mildly and moderately hyperplastic solitary NE cells and NEBs tend to express the hormones indigenous to the bronchi, whereas in the severely hyperplastic and dysplastic cells, "ectopic" hormones may also be expressed; the latter include predominantly ACTH and vasoactive intestinal polypeptide. A distinct hyperplasia of NEBs has been found in the lungs from individuals living at altitudes ranging from 3400 to 4300 meters; these changes may represent an adaptive response to chronic hypoxia parallel to the hyperplastic carotid paraganglia that may be found in the same type of population. Bronchopulmonary NE neoplasms comprise a spectrum that includes typical carcinoids, well-differentiated NE carcinomas, and NE carcinomas of intermediate and small cell types. Typical carcinoids are predominantly central, display little if any pleomorphism, are richly granulated by electron microscopy, and by immunohistochemistry express predominantly, although not exclusively, hormones indigenous to their site of origin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Neuroendocrine components of the bronchopulmonary tract: hyperplasias, dysplasias, and neoplasms. 613 58

Endogenous opioid peptides are present in cerebral perivascular nerves and in the CSF, and their concentrations are changing in response to stimuli that activate regulatory mechanisms of the cerebral circulation (e.g., alterations of the perfusion pressure or changes of the arterial O2 tension). Opiate receptors are expressed in the cells of the CNS and the cerebrovascular bed, and their activation modulates the function of other vasoregulatory mechanisms (i.e., the autonomic nervous system, nitric oxide, prostanoids, vasopressin) that are involved in the control of the cerebrovascular tone. The direct vasomotor effects of opioid peptides and opiates on the cerebral arteries under in vitro or in situ conditions appear to be weak or absent in several species. However, Met- and Leu-enkephalin induce pial arterial vasodilation in the newborn pig. In this species, beta-endorphin acts as a constrictor, whereas dynorphin may induce either dilation or constriction depending on the experimental conditions. The influence of exogenously applied natural and synthetic opioids on the cerebral blood flow (CBF) is determined mainly by their metabolic, neuronal, and respiratory effects. Hypothalamic and pituitary circulations are especially sensitive to opioids. Under resting conditions, endogenous opioid peptides do not participate in the regulation of the cerebrovascular tone and CBF. On the other hand, mu and delta opiate receptor stimulation by endogenous opioid peptides, interacting with other vasoactive factors, obviously contributes to the hypoxia- and hypercapnia-induced cerebral vasodilation. Furthermore, endogenous opioid mechanisms are involved in the autoregulation of the hypothalamic blood flow. Thus, the endogenous opioid system may well represent a latent regulatory mechanism, which is of limited importance under basal conditions, but becomes more important under conditions of stress. Synthetic exogenous opioids do not appear to influence the hypoxic or hypercapnic CBF responses or the cerebral autoregulatory process.
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PMID:Opiate receptor-mediated mechanisms in the regulation of cerebral blood flow. 896 68