Participation of opioid receptors in the modulation of the analgesic response by adrenal and gonadal glands.

The involvement of opioid receptors in the analgesic response was evaluated by the tail-immersion test in simultaneously adrenalectomized and ovariectomized female Wistar rats (210-250 g). The reaction time (mean +/- SEM) for tail withdrawal from hot water decreased significantly 2 weeks after surgery (3.52 +/- 0.20 s) when compared to intact animals (6.09 +/- 0.23 s). Hormonal replacement with dexamethasone (50 micrograms/day) did not affect reaction time (3.38 +/- 0.19 s). However, this response was restored by combined adrenal and gonadal steroid substitution (estradiol 5 micrograms/day and progesterone 1.5 micrograms 6 h before the tests) therapy (5.11 +/- 0.45 s in animals treated with dexamethasone plus estradiol and 5.04 +/- 0.43 s in animals treated with dexamethasone plus estradiol plus progesterone). Naloxone (2 mg/kg) decreased the reaction time of animals treated with adrenal and gonadal steroids (5.11 +/- 0.45 vs 4.15 +/- 0.44 s and 5.04 +/- 0.43 vs 3.87 +/- 0.28 s, respectively, before and after naloxone) but failed to decrease it in rats treated with dexamethasone only (3.88 +/- 0.18 vs 4.34 +/- 0.25 s, before and after naloxone). These observations indicate that gonadal steroids are the most important steroid factors involved in the reaction time to tail immersion in hot water and confirm other reports that the opioid pathways modulating the neuronal circuitry require the presence of these hormones.

Participation of opioid receptors in the modulation of the analgesic response by adrenal and gonadal glands

The invovlement of opiodi receptors in the analgesic response was evaluated by the tail-immersion test in simultaneously adrenalectomized and ovariectomized female Wistar rats (210-250g). The reaction time (mean ñ SEM) for tail withdrawal from hot water decreased significantly 2 weeks after surgery (3.52 ñ 0.20 s) when compared to intact animals (6.09 ñ 0.23 s). Hormonal replacement with dexamethasone (50*/day) did not affect reaction time (3.38 ñ 0.19 s). However, this response was restored by combined adrenal and gonadal steroid substitution (estradiol 5*g/day and progesterone 1.5*g 6h before the test) therapy (5.11 ñ 0.45 s) in animal treated with dexamethasone plus estradiol and 5.04 ñ 0.43 s in animals treated with dexamethasone plus estradiol plus progesterone). Naloxone (2mg/Kg decreased the reaction time of animals treated with adrenal and gonadal steroids (5.11 ñ 0.45 vs 4.15 ñ 0.44 and 5.04 ñ 0.43 vs 3.87 ñ 0.28 s, respectively, before and after naloxone) but failed to decrease it in rats treated with dexamethasone only (3.88 ñ 0.18 vs 4.34 ñ 0.25 s, before and after naloxone). These observations indicate that gonadal steroids are the most important steroid factors involved in the reaction time to tail immersion in hot water and confirm other reports that the opioid pathways modulating the neuronal circuitry require the presence of these hormones

[Relationship between the renal electrical impedance variations with glomerular filtration rate changes in dogs (author's transl)]. / Relação entre as variações da impedância elétrica renal com alterações da taxa de filtração glomerular em cães

Records of the electrical impedance were obtained by means of surface electrodes placed on ventral and dorsal sides of the left kidney of anesthetized dogs. Changes of the renal electrical impedance resulted from alterations of the glomerular filtration rate caused by decrease of blood renal pressure to 80 and 50 mm Hg either due to constriction of the aorta or bleeding. The relation were established also by using physiological solution's infusion. The results showed that changes of the means of renal electrical impedance were in opposite direction to changes in glomerular filtration rate. The electrodes employed were constituted of two parts: one fixed and another adjustable and flexible, possibiliting a good contact with the renal surface independently of the kidney size.