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. .

Effect of pain related of sex and estrous cycle on blood plasma glucose, free fatty acids and corticosterone in rats / Resposta de dor relacionada ao sexo e ciclo estral em concentrações plasmáticas de glicose, ácidos graxos livres e corticosterona em ratos

Sex differences related with pain have been studied and evidences suggesting influence of sex steroid hormones on the thresholds of pain. Experimental nociception has been test using formalin as a model of nociceptive stimulus. Association of stress, pain and metabolic and hormonal changes has not been explored. The aim of this study was to compare metabolic and hormonal changes between male rats and female rats in proestrus and estrus cycle after painful stimulus by formalin into the masseter muscle. Male and female Wistar rats (200-250 g b.w.) were submitted to an injection of formalin (F, 1.5%) or saline (S, 9.9%) into the masseter muscle and after 0 (N, control group without injection), 5, 15, 30 or 60 minutes they were decapitate and blood was collected to measure biochemical parameters. Plasma estradiol concentration (pg dL-1) was significantly higher in proestrus (106.3  4.3, n = 45, p < 0.05) group compared to the estrous group (89.4  3.5, n = 43). Blood plasma concentration of glucose (mg dL-1) was increased after 5 and 15 minutes of injection of formalin or saline in the animals, but in the estrus group the increase was bigger than in the others. Free fatty acids levels increased in the estrous group after 5, 15 and 30 minutes and also the corticosterone levels and these concentrations were significantly different (p < 0.05) from either male or female animals in proestrus state. The results obtained suggesting that estradiol is related to a sensibility to pain and the estrus stage is related to stress and the estrous cycle has a modulator effect on pain and nociceptive sensibility.

Estudos experimentais têm demonstrado a existência de diferenças sexuais na resposta de dor, e as evidências sugerem a influência de hormônios sexuais na experiência dolorosa. O objetivo deste estudo foi o de comparar as alterações metabólicas e hormonais entre machos e fêmeas em proestro e estro após o estímulo doloroso por formalina no músculo masseter. Ratos machos e fêmeas Wistar (peso: 200-250 g) foram submetidos a uma injeção de formalina (grupo F, 1,5%) ou salina (grupo S, 9,9%) no músculo masseter e depois de 0 (grupo N, controle sem injeção), 5, 15, 30 ou 60 minutos foram decapitados e retirou­se o sangue para dosagens bioquímicas. A concentração plasmática de estradiol (pg dL-1) foi significativamente maior no proestro (106,3 ± 4,3, n = 45, p < 0,05) em comparação com o grupo em estro (89,4 ± 3,5, n = 43). A concentração sanguínea de glicose plasmática (mg dL-1) aumentou após 5 e 15 minutos da injeção de formalina ou salina nos animais, mas no grupo estro o esse aumento foi maior. A concentração plasmática de ácidos graxos livres e de corticosterona demonstrou níveis elevados no grupo estro após 5, 15 e 30 minutos apresentando uma diferença significante (p < 0,05) em relação aos animais machos ou fêmeas em proestro. Os valores de glicose, ácidos graxos livres e corticosterona mais elevados nas fêmeas em estro sugerem que a fase do ciclo estral pode estar interferindo na resposta de estresse, podendo estar relacionada com a diminuição na concentração de estradiol.