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31. Carotid Body Volume in Three-Weeks-Old Rats Having an Episode of Neonatal Anoxia.

Author

BACK, NATHAN, COHEN, IRUN R., KRITCHEVSKY, DAVID, LAJTHA, ABEL, PAOLETTI, RODOLFO, Hayashida, Yoshiaki, Gonzalez, Constancio, Kondo, Hisatake, SAIKI, CHIKAKO, MAKINO, MASAYA, and MATSUMOTO, SHIGEJI

Abstract

The development of oxygen chemosensitivity in carotid chemoreceptor cells, i.e. type I cell (glomus cell), is reported to continue postnatally (Wasicko et al., 1999), and it has been suggested that environmental experiences such as episode of hypoxia and chronic hypoxia during critical period of maturation may result in long-term alterations in the structure or function of the respiratory control neural network (Carroll, 2003). In the previous studies, we have observed no apparent effect on the hypoxic ventilatory response (HVR) in the day 7 newborn rats, which had daily episode of anoxia from day 1 to day 6 (day 0 = day of birth) (Saiki and Mortola, 1994), but significantly higher HVR in the 3-weeks-old rats, which had an episode of anoxia on day 3-4 after birth (Saiki and Matsumoto, 1999). These results suggest that the severity of anoxia and the timing of the anoxic episode as well as the assessment of HVR may be important factors, and that an episode of anoxia during the neonatal period has long-lasting effects on the control of ventilation in rats. Because no further information is available on the effects, including carotid body chemoreceptors, we examined whether or not an episode of anoxia in neonatal period induces changes in the carotid body and glomus cell structures in the three-weeks-old rats. [ABSTRACT FROM AUTHOR]

Published
2006
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50. Effect of α1-adrenergic receptor antagonist on the noradrenaline-induced facilitation in respiratory rhythm in newborn rat pons-medulla-spinal cord preparations

Author

Makino, Masaya, Saiki, Chikako, and Matsumoto, Shigeji

Subjects
*ADRENERGIC receptors, *PRAZOSIN, *NORADRENALINE, *RESPIRATORY organs
Abstract

Abstract: We hypothesized that facilitation of respiratory rhythm by noradrenaline (NA) in rat pons-medulla-spinal cord preparations is mediated through α1-adrenergic receptors. In 0- to 4-day-old rats, the respiratory frequency (f R) was monitored at the C4 ventral root and trigeminal motor (V MO) outputs. f R at temperature (Te)=23°C was lower than that at a higher Te (27°C) and was increased by NA. At 23°C, lower concentrations of NA were needed to produce the same increases in f R seen at 27°C. With highest NA concentration we tested (50μM), activity at C4 was maintained in all preparations at both Te, whereas that at V MO was maintained in 50% (27°C) or 88% (23°C) of the preparations. Particularly, tonic activity at C4 appeared in all preparations at both Te, but that at the V MO occurred in 0% (27°C) or 18% (23°C) of the preparations. Based on these results, we used the lower Te (23°C) and applied a low concentration of NA (3μM) to the preparations. We found that: (1) with the addition of NA, f R was increased without the occurrence of tonic activity and (2) NA-related f R facilitation was inhibited by pre-treatment with the α1-adrenergic receptor antagonist prazosin (2μM). f R was increased by application of the α1-adrenergic receptor agonist phenylephrine (4μM), and this response was inhibited by prazosin (4μM). At Te=23°C, f R facilitation by NA in newborn rat pons-medulla-spinal cord preparations was obtained by activation of α1-adrenergic receptors. [Copyright &y& Elsevier]

Published
2006
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