RESUMO
Lidocaine, a local anesthetic, produces seizures by unknown central mechanisms. The objective of this study was to investigate the effect of cellular metabolism alteration, by changing thyroid hormones levels, on susceptibility to lidocaine-kindling. Lidocaine was administered daily (60 mg/Kg x day, i.p.) to rats treated with thyroxine (300 microg/Kg x day) or methimazole (60 mg/Kg day), dissolved in drinking water. After the 18th lidocaine administration, the cumulative percent of animals convulsed was higher (100%) for the methimazole-treated group and lower (20%) for the thyroxine-treated group, compared to the control group (40%). The results suggest that susceptibility to lidocaine-kindling depends on neuronal metabolism, which probably affects monoamines uptake mechanisms.
Assuntos
Excitação Neurológica/fisiologia , Hormônios Tireóideos/fisiologia , Análise de Variância , Anestésicos Locais/efeitos adversos , Anestésicos Locais/farmacologia , Animais , Excitação Neurológica/efeitos dos fármacos , Lidocaína/efeitos adversos , Lidocaína/farmacologia , Modelos Animais , Ratos , Ratos Wistar , Convulsões/induzido quimicamente , Convulsões/metabolismoRESUMO
It is known that lactation induces a mild hypothyroid state in rats and other mammals while thyroid hormone administration increases milk secretion in ruminants. The aim of this study was to investigate the effects of a moderate dose of 3,5,3'-triiodothyronine (T3), administered to rat dams during lactation on pups' growth and milk yield and composition. Primiparous Wistar rats with litters adjusted to 10 pups per dam received either tap water or T3 (75 microg/kg x day) in their drinking water from parturition till weaning. Food and water intake of dams and body weight of dams and pups were measured daily. In other groups of rats with similar treatments, milk yield of dams, macronutrient milk composition, and mammary arteriovenous differences for triglycerides (TG) and glucose were also determined. Dams treated with T3 ingested more food and their pups gained more weight than controls. Milk yield, milk TG concentration and glucose extraction by mammary glands were also higher in T3 treated dams. The results show that compensation of the mild hypothyroidism of the lactating rat may contribute to an increase in milk production and lipid levels, leading to an increase in growth of pups.
Assuntos
Animais Recém-Nascidos/crescimento & desenvolvimento , Lactação/efeitos dos fármacos , Leite/efeitos dos fármacos , Triglicerídeos/metabolismo , Tri-Iodotironina/farmacologia , Animais , Peso Corporal/efeitos dos fármacos , Feminino , Leite/fisiologia , Ratos , Ratos Wistar , Tri-Iodotironina/administração & dosagemRESUMO
The effects of 3,5,3'-triiodothyronine (T3) levels on threshold, latency and duration of pentylenetetrazole-induced seizures were tested in rats treated with thyroxine (300 micrograms/kg.day, N = 9) or methimazole (60 mg/kg.day, N = 5) dissolved in drinking water. Compared to controls (N = 7), methimazole treatment reduced T3 levels (45.4 +/- 2.0 vs. 33.0 +/- 4.8 ng/dl) and increased seizure duration (36.2 +/- 22.4 vs. 289.6 +/- 24.4 s) and threshold (29.0 +/- vs. 45.5 mg/kg). Thyroxine treatment increased T3 levels (45.4 +/- 2.0 vs. 67.7 +/- 4.8 ng/dl), but had no significant effect on seizures.