Vagal afferent activity and body temperature in 3 to 10-day-old and adult rats.

This study examined the possible contribution of vagal stretch receptor activity to the increased power of the Hering-Breuer reflex in hyperthermia in rats during the early postnatal period. Experiments were performed on 10 anesthetized (pentobarbital 40 mg/kg, i.p.) 3 to 10-day-old (body weight of 16 +/- 1 g; SE) and, for comparison, 18 adult Sprague-Dawley rats (body weight of 336 +/- 35 g). Animals were tracheostomized and artificially ventilated with oxygen. The left vagus nerve was cut. In adult animals, single receptor fibers or a bundle of a few fibers were recorded using a bipolar stainless-steel electrode under mineral oil. In the young rats, a suction electrode filled with normal saline was used. Positive pressure of either 5 or 10 cmH2O was applied to the trachea when the respirator was turned off. The vagal activity was amplified and monitored on a storage oscilloscope for calculation of the frequency of vagal afferent activity during a given pressure application at different rectal temperatures (T(R); range 28 to 42 degrees C). In total, 30 and 31 sets of vagal activity in the young and adult rats, respectively, were analyzed. In all cases, an increase in tracheal pressure (P(TR)) from 5 to 10 cmH2O increased the frequency of vagal firing. The increase was greater in the adult versus the young animals; at 36 degrees C the increase was 49 +/- 11% and 16 +/- 3% in the adult and young rats, respectively (P < 0.01). In all animals, vagal receptors showed temperature-sensitivity, but less so in the young than in the adult rats (P < 0.0004 and P < 0.003; for P(TR) of 5 and 10 cmH2O, respectively). In addition, the relationship between temperature-sensitivity and T(R) had significant slopes (P < 0.001 for both inflation pressures) in the adults but not in the young rats, indicating that in the latter the temperature-sensitivity of vagal receptors is independent of TR. These results imply that temperature-sensitivity of vagal receptors could have contributed to the increased power of the Hering-Breuer reflex in rats during the early postnatal period in the warmer environment.

[1]  J. Aranda,et al.  Interaction of caffeine and continuous distending airway pressure in neonatal apnea. , 2008, American journal of perinatology.

[2]  J. Remmers,et al.  Significance of vagal innervation in perinatal breathing and gas exchange. , 2000, Respiration physiology.

[3]  D. Merazzi,et al.  Hering-Breuer reflex in conscious newborn rats: effects of changes in ambient temperature during hypoxia. , 1999, Journal of applied physiology.

[4]  T. Trippenbach,et al.  Interaction between somatic and vagal afferent inputs in control of ventilation in 2-week-old rabbits. , 1999, Respiration physiology.

[5]  D. Merazzi,et al.  Effects of Changes in Ambient Temperature on the Hering-Breüer Reflex of the Conscious Newborn Rat , 1999, Pediatric Research.

[6]  J. Mortola,et al.  Hering-Breüer reflexes in high-altitude infants. , 1995, Clinical science.

[7]  S. England,et al.  Importance of vagal afferents in determining ventilation in newborn rats. , 1988, Journal of applied physiology.

[8]  N. Cherniack,et al.  Cooling the intermediate area of the ventral medullary surface affects tracheal responses to hypoxia. , 1987, Respiration physiology.

[9]  J. Fisher,et al.  Effects of hypoxia on lung mechanics in the newborn cat. , 1987, Canadian journal of physiology and pharmacology.

[10]  D. Marlot,et al.  Effects of tonic vagal input on breathing pattern in newborn rabbits. , 1985, Journal of applied physiology.

[11]  J. Farber,et al.  Developmental morphometry of the vagus nerve in the opossum. , 1985, Brain research.

[12]  G. Sant'ambrogio,et al.  Airway and lung receptors and their reflex effects in the newborn , 1985, Pediatric pulmonology.

[13]  G. Sant'ambrogio,et al.  Location and discharge properties of respiratory vagal afferents in the newborn dog. , 1982, Respiration physiology.

[14]  B. Duron,et al.  Functional localization of pulmonary stretch receptors in the tracheobronchial tree of the kitten. , 1982, Canadian journal of physiology and pharmacology.

[15]  J. Jansen,et al.  Developmental morphometry and physiology of the rabbit vagus nerve. , 1982, Brain research.

[16]  G. Sant'ambrogio.  Information arising from the tracheobronchial tree of mammals. , 1982, Physiological Reviews.

[17]  C. Gaultier,et al.  Hering-Breuer inflation reflex in young and adult mammals. , 1981, Canadian journal of physiology and pharmacology.

[18]  T. Trippenbach.  Laryngeal, vagal and intercostal reflexes during the early postnatal period. , 1981, Journal of developmental physiology.

[19]  D. Bartlett,et al.  Adaptation of pulmonary stretch receptors in different mammalian species. , 1979, Respiration physiology.

[20]  G. Bradley,et al.  The transduction properties of tracheal stretch receptors in vitro. , 1977, Respiration physiology.

[21]  P. Jeffery,et al.  Location of stretch receptors in the trachea and bronchi of the dog. , 1976, The Journal of physiology.

[22]  C. von Euler,et al.  Temperature effects on the inflation reflex during expiratory time in the cat. , 1976, Acta physiologica Scandinavica.

[23]  M. Younes,et al.  Interaction between chemical factors and duration of apnea following lung inflation. , 1974, Journal of applied physiology.

[24]  P. Dejours,et al.  Factors influencing the intensity of the Breuer-Hering inspiration-inhibiting reflex. , 1970, Respiration physiology.

[25]  K. W. Cross,et al.  The response of the new‐born baby to inflation of the lungs , 1960, The Journal of physiology.

[26]  J. Mortola,et al.  Effects of hypoxia and hypercapnia on the Hering-Breuer reflex of the conscious newborn rat. , 1995, Journal of applied physiology.

[27]  S. Iscoe,et al.  Bronchomotor responses to hypoxia and hypercapnia in decerebrate cats. , 1995, Journal of applied physiology.

[28]  B. Duron,et al.  Postnatal maturation of phrenic, vagus, and intercostal nerves in the kitten. , 1979, Biology of the Neonate.

[29]  B. Duron,et al.  Postnatal development of vagal control of breathing in the kitten. , 1979, Journal de physiologie.

[30]  Schoener Ep,et al.  Effect of hyperthermia and Pa CO2 on the slowly adapting pulmonary stretch receptor. , 1972 .

[31]  Schwieler Gh.  Respiratory regulation during postnatal development in cats and rabbits and some of its morphological substrate. , 1968 .

[32]  A. Hamberger.  Difference between isolated neuronal and vascular glia with respect to respiratory activity. , 1963, Acta physiologica Scandinavica. Supplementum.