RESUMEN
In the present study we evaluated the possible modulatory role of noradrenaline on the neurotransmission of the peripheral chemoreflex afferents in the caudal commissural NTS of awake rats. To reach this goal we performed a dose-response curve to microinjection of increasing dose of noradrenaline into the caudal commissural NTS of awake rats and then the threshold dose, which produces minor changes in the baseline mean arterial pressure, was selected to be used in the chemoreflex experiment. The peripheral chemoreflex was activated with KCN before and after bilateral microinjections of noradrenaline (5 nMol/50 nL, threshold dose) into the NTS. The data show that microinjection of noradrenaline into the caudal NTS produced a significant reduction in the pressor response to the chemoreflex 30 s after the injection when compared to the control response (30+/-6 vs. 49+/-3 mm Hg) but no significant changes in the bradycardic response. The data indicate that noradrenaline in the caudal commissural NTS of awake rats may play an important inhibitory neuromodulatory role on the processing of the pressor/sympathoexcitatory component of the chemoreflex.
Asunto(s)
Presión Sanguínea/fisiología , Células Quimiorreceptoras/fisiología , Inhibición Neural/fisiología , Norepinefrina/metabolismo , Reflejo/fisiología , Núcleo Solitario/fisiología , Animales , Presión Sanguínea/efectos de los fármacos , Bradicardia/inducido químicamente , Fenómenos Fisiológicos Cardiovasculares/efectos de los fármacos , Células Quimiorreceptoras/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Masculino , Microinyecciones , Inhibición Neural/efectos de los fármacos , Norepinefrina/farmacología , Sistema Nervioso Parasimpático/efectos de los fármacos , Sistema Nervioso Parasimpático/fisiología , Cianuro de Potasio/farmacología , Ratas , Ratas Wistar , Reflejo/efectos de los fármacos , Núcleo Solitario/efectos de los fármacos , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/fisiología , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Vasoconstricción/efectos de los fármacos , Vasoconstricción/fisiología , Vasoconstrictores/metabolismo , Vasoconstrictores/farmacología , Vasodilatación/efectos de los fármacos , Vasodilatación/fisiología , Aferentes Viscerales/efectos de los fármacos , Aferentes Viscerales/fisiología , Vigilia/fisiologíaRESUMEN
Extra-cellular production of a novel galactose oxidase from Fusarium acuminatum using submerged fermentation was studied. Glucose (1.0% w/v) was used as the sole carbon source. Maximum galactose oxidase production (approximately 4.0 U/ml) was obtained when fermentation was carried out at 25 degrees C, with orbital shaking (100 rpm) and an initial medium of pH 7.0, for 96 h, using a 2% (v/v) inoculum made from a homogenized four-day-old liquid culture, in the presence of copper, manganese, and magnesium. The enzyme was purified by one-step affinity chromatography, with a recovery of 42% of the initial activity. The purified enzyme ran as a single band of 66 kDa in SDS-PAGE. Optimal pH and temperature for the enzyme activity were 8.0 and 30 degrees C, respectively. The enzyme was thermoinactivated at temperatures above 60 degrees C. The purified enzyme was active toward various substrates, including galactose, dihydroxyacetone, guar gum, lactose, melibiose, methyl-galactopyranoside, and raffinose. SDS was an inhibitor but EDTA, Tween 80, NH(4)(+), Na(+), Mg(2+), K(+), and glycerol were not. The Michaelis-Menten constant (K(m)) for galactose was estimated to be 16.2 mM, while maximal velocity (V(max)) was 0.27 micromol of H(2)O(2) . ml(-1) . min(-1).