Carotid chemoreceptors

Lobelia chinensis L. L. pyramidalis Wallich. L. sessilifolia Lambert Ban Bian Lian Sha Gen Cai (Lobelia) (whole plant) Lobeline, lobelanine, lobelanidine, isolobelamine. (Lobeline has been approved by the FDA to curb the tobacco habit).33-50-71 This herb may be toxic. Diuretic, increase respiration via stimulation of carotid chemoreceptors. Treat snakebites, insecticide, reduce swelling, depurative, antirheumatic, antisyphilitic. 

Tissue hypoxia occurs within 4 minutes of failure to deliver adequate supply. Hyperventilation due to carotid chemoreceptor stimulation becomes noticeable when P02 falls to 5.3. Arterial oxygen saturation should be between 95-100%. This patient has a good saturation figure of 99.6%. 

Doxapram increases the tidal volume and respiratory rate by stimulating carotid chemoreceptors. Its use has been limited since the introduction of non-invasive ventilatory techniques for respiratory failure. 

Chemosensory Response, but not the Hypercapnic Chemosensory Response of the Carotid Chemoreceptor (Mulligan and Lahiri, 1982). 237... 

When the effect of PaO2 is lost, although the PaCO, effect is normal, it is due primarily to central chemoreceptor stimulation. The indications are that the stimulation due to carotid chemoreceptor is minimal (Milledge and Lahiri, 1967). 

After exposure of cats to normobaric hypero da for over 36 h, their carotid chemoreceptors did not respond to hypoxia but responded to hypercapnia with an overshoot and enhanced activity. The overshoot was abolished after inhibition of carbonic anhydrase with acetazolamide, showing that carotid body chemoreception responded to H+ (Lahiri et al., 1987). 

Prabhakar NR, Mitra J, ChemiackNS, 1987. Role of substance P in hypercapnic excitation of carotid chemoreceptors. J Appl Physiol 63 2418-2425. 

The dynamic response of the peripheral chemoreceptors to Pa02 maybe modeled in a similar fashion but the steady-state response is hyperbolic [Cunningham et al, 1986]. Furthermore, hypoxia and hypercapnia have a multiplicative effect on carotid chemoreceptor discharge [Fitzgerald and Lahiri, 1986],... 

Hashimoto K, Igarashi S, Uei I, Kumakura S (1964) Carotid chemoreceptor reflex effects on coronary flow and heart rate. Am J Physiol 206 536-540... 

The rapid onset of the bradycardia in response to hypoxia is suggestive of a neural reflex (Fig. 2). The sensors for this reflex have been identified as the carotid chemoreceptors (27,28), which send afferent fibers in the carotid sinus nerve to a central integrating area in the brainstem (29) and whose efferent arm consists of parasympathetic cholinergic fibers to the heart carried in the vagus nerve (cranial nerve X) and a-adrenergic sympathetic fibers to resistance vessels in peripheral vascular beds (30). The absence of this bradycardic response earlier in gestation (31) is indicative of immaturity of neural reflex mechanisms. 

Blanco CE, Hanson MA, McCooke HB. Effects on carotid chemoreceptor resetting of pulmonary ventilation in the fetal lamb in utero. J Dev Physiol 1988 10 167—174. 

Jansen AH, Ioffe S, Russell BJ, Chemick V Effect of carotid chemoreceptor denervation on breathing in utero and after birth. J Appl Physiol 1981 51 630-633. Purves MJ. The effects of h3fpoxia in the new-born lamb before and after denervation of the carotid chemoreceptors. J Physiol 1966 185 60-77. 

Forster HV Pan LG, Lowry TF, Serra A, Wenninger J, Martino P. Important role of carotid chemoreceptor afferents in control of breathing of adult and neonatal mammals. Respir Physiol 2000 119 199-208. 

Mulligan E, Alsberge M, Bhide S. Carotid chemoreceptor recording in the newborn piglet. In Eyzaguirre C, Fidone SJ, Fitzgerald RS, Lahiri S, McDonald D, eds. Arterial Chemoreception. New brk Springer. 1990 285-289. 

Marchal F, Bairam A, Haouzi P, Crance JP, Di Giulio C, Vert P, Lahiri S. Carotid chemoreceptor response to natural stimuli in the newborn kitten. Respir Physiol 1992 87 183-193. 

Carroll JL, Bamford OS, Fitzgerald RS. Postnatal maturation of carotid chemoreceptor responses to O2 and CO2 in the cat. J Appl Physiol 1993 75 2383-2391. 

Kholwadwala D, Donnelly DF. Maturation of carotid chemoreceptor sensitivity to h3q)oxia in vitro studies in the newborn rat. J Physiol 1992 453 461-473. 

Postnatal Maturation of the Carotid Chemoreceptor O2 Sensitivity at the Cellular Level... 

Perhaps surprisingly, given their importance in the developing infant, the carotid chemoreceptors have minimal sensitivity to hypoxia at birth and become more sensitive over the first few days or weeks of life (10-16). Increasing hypoxia sensitivity of the arterial chemoreceptors after birth is termed resetting, and it occurs in both carotid and aortic chemoreceptors (17). Carotid chemoreceptor resetting appears to be modulated by the 4-fold rise in arterial O2 tension that occurs at birth (18-22), raising the possibility that peri- and postnatal hypoxia may impair carotid chemoreceptor development. In addition, perinatal hyperoxia causes... 

Figure 1 Elements of carotid chemoreceptor O2 transduction pathway. See text for...

In every species studied to date, the carotid chemoreceptor response to hypoxia increases with postnatal age. In in vitro carotid body preparations, the peak nerve discharge in response to a potent hypoxia stimulus increases about fourfold in neonatal rats during the first month, with most of that change occurring by 2 weeks (10,12,45) (Fig. 2). Similar patterns of postnatal maturation of carotid sinus nerve... 

Figure 2 Summary of rat carotid chemoreceptor maturation. All plots depict responses to a strong hypoxia stimulus. Hypoxia-induced CSN activity, catecholamine secretion, and intracellular calcium responses all increase over approximately the same time course. (Data adapted from Refs. 10,12,45,68.)...

Table 1 Potential Sites of Postnatal Carotid Chemoreceptor Developmental Changes...

Type I cells were enzymatically dissociated from the carotid chemoreceptors of newborn and adult rabbits and studied using the fluorescent dye fura-2 (71). [Ca " "] responses to hypoxia were three- to flvefold larger in type I cells from adult versus newborn rabbits, while responses to ionomycin (a Ca ionophore) did not... 

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