Effect of chronic ethanol exposure on rat ventilatory responses to hypoxia and hypercapnia.
OBJECTIVE
The effect of chronic ethanol exposure on chemoreflexes has not been extensively studied in experimental animals. Therefore, this study tested the hypothesis that known ethanol-induced autonomic, neuroendocrine and cardiovascular changes coincide with increased chemoreflex sensitivity, as indicated by increased ventilatory responses to hypoxia and hypercapnia.


METHODS
Male Wistar rats were subjected to increasing ethanol concentrations in their drinking water (first week: 5% v/v, second week: 10% v/v, third and fourth weeks: 20% v/v). At the end of each week of ethanol exposure, ventilatory parameters were measured under basal conditions and in response to hypoxia (evaluation of peripheral chemoreflex sensitivity) and hypercapnia (evaluation of central chemoreflex sensitivity).


RESULTS
Decreased respiratory frequency was observed in rats exposed to ethanol from the first until the fourth week, whereas minute ventilation remained unchanged. Moreover, we observed an increased tidal volume in the second through the fourth week of exposure. The minute ventilation responses to hypoxia were attenuated in the first through the third week but remained unchanged during the last week. The respiratory frequency responses to hypoxia in ethanol-exposed rats were attenuated in the second through the third week but remained unchanged in the first and fourth weeks. There was no significant change in tidal volume responses to hypoxia. With regard to hypercapnic responses, no significant changes in ventilatory parameters were observed.


CONCLUSIONS
Our data are consistent with the notion that chronic ethanol exposure does not increase peripheral or central chemoreflex sensitivity.
Department of Physiology, Dental School of Ribeirao Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
João Paulo J
JP
Sabino
Department of Physiology, School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Andreia Lopes da
AL
Silva
Department of Pharmacology, School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Leonardo B
LB
Resstel
Department of Physiology, School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Jose
J
Antunes-Rodrigues
Department of Physiology, School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Mogens L
ML
Glass
Department of Physiology, Dental School of Ribeirao Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Luiz G S
LG
Branco
D000818:Animals; D000431:Ethanol / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D023421:Models, Animal; D012123:Pulmonary Ventilation / Q000187:drug effects*; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology; D015656:Respiratory Mechanics / Q000187:drug effects; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors
D000431:Ethanol