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Query: UMLS:C0020440 (
hypercapnia
)
7,939
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Sighs, a well-known phenomenon in mammals, are substantially augmented by hypoxia and
hypercapnia
. Because (d-Ala(2),N-Me-Phe(4),Gly-ol)-enkephalin (
DAMGO
), a mu-receptor agonist, injected intravenously and locally in the caudal medullary raphe region (cMRR) decreased the ventilatory response to hypoxia and
hypercapnia
, we hypothesized that these treatments could inhibit sigh responses to these chemical stimuli. The number and amplitude of sighs were recorded during three levels of isocapnic hypoxia (15%, 10%, and 5% O(2) for 1.5 min) or
hypercapnia
(3%, 7%, and 10% CO(2) for 4 min) to test the dependence of sigh responses on the intensity of chemical drive in anesthetized and spontaneously breathing rats. The role of mu-receptors in modulating sigh responses to 10% O(2) or 7% CO(2) was subsequently evaluated by comparing the sighs before and after 1) intravenous administration of
DAMGO
(100 microg/kg), 2) microinjection of
DAMGO
(35 ng/100 nl) into the cMRR, and 3) intravenous administration of
DAMGO
after microinjection of d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP, 100 ng/100 nl), a micro-receptor antagonist, into the cMRR. Hypoxia and
hypercapnia
increased the number, but not amplitude, of sighs in a concentration-dependent manner, and the responses to hypoxia were significantly greater than those to
hypercapnia
. Systemic and local injection of
DAMGO
into the cMRR predominantly decreased the number of sighs, while microinjection into the rostral and middle MRR had no or limited effects. Microinjecting CTAP into the cMRR significantly diminished the systemic
DAMGO
-induced reduction of the number of sighs in response to hypoxia, but not to
hypercapnia
. Thus we conclude that hypoxia and
hypercapnia
elevate the number of sighs in a concentration-dependent manner in anesthetized rats, and this response is significantly depressed by activating systemic mu-receptors, especially those within the cMRR.
...
PMID:Activation of opioid micro-receptors in medullary raphe depresses sighs. 1924 86
We tested the hypothesis that mu-opioid receptors (MORs) in the caudomedial nucleus tractus solitarius (cmNTS) are important for the ventilatory responses to stimulation of bronchopulmonary C-fibers (PCFs), the carotid body-mediated hypoxia, and
hypercapnia
independent of the carotid body. First, we used immunohistochemistry to map MORs distribution in the caudal medulla. Then we compared the effects of intra-cmNTS microinjection of
DAMGO
(a MOR agonist) with or without a combination of CTAP (a MOR antagonist) on the ventilatory responses to: 1) right atrial injection of capsaicin (to stimulation of PCFs) and 2) acute hypoxia (HVR, to stimulate the carotid body) in awake intact rats; and 3)
hypercapnia
(HCVR) in the carotid body ablated rats. The cmNTS presented the highest MORs in the caudal medulla. Microinjection of
DAMGO
blocked the PCF-mediated apnea, attenuated HVR (70%) and HCVR (21%), while microinjection of CTAP+DAMGO failed to affect these chemoreflexes. Our data demonstrate a critical role of activation of cmNTS MORs in regulating these chemoreflexes and imply a presence of MORs in the synapse of the 2nd-order neurons receiving inputs from PCFs and the carotid body, and NTS chemosensitive neurons.
...
PMID:Mu-opioid receptors in the caudomedial NTS are critical for respiratory responses to stimulation of bronchopulmonary C-fibers and carotid body in conscious rats. 2774 12
