Acute effect of amiodarone on cardiovascular reflexes of normotensive and renal hypertensive rats

The aim of the present study was to evaluate the effect of amiodarone on mean arterial pressure (MAP), heart rate (HR), baroreflex, Bezold-Jarisch, and peripheral chemoreflex in normotensive and chronic one-kidney, one-clip (1K1C) hypertensive rats (N = 9 to 11 rats in each group). Amiodarone (50 mg/kg, iv) elicited hypotension and bradycardia in normotensive (-10 ± 1 mmHg, -57 ± 6 bpm) and hypertensive rats (-37 ± 7 mmHg, -39 ± 19 bpm). The baroreflex index (deltaHR/deltaMAP) was significantly attenuated by amiodarone in both normotensive (-0.61 ± 0.12 vs -1.47 ± 0.14 bpm/mmHg for reflex bradycardia and -1.15 ± 0.19 vs -2.63 ± 0.26 bpm/mmHg for reflex tachycardia) and hypertensive rats (-0.26 ± 0.05 vs -0.72 ± 0.16 bpm/mmHg for reflex bradycardia and -0.92 ± 0.19 vs -1.51 ± 0.19 bpm/mmHg for reflex tachycardia). The slope of linear regression from deltapulse interval/deltaMAP was attenuated for both reflex bradycardia and tachycardia in normotensive rats (-0.47 ± 0.13 vs -0.94 ± 0.19 ms/mmHg and -0.80 ± 0.13 vs -1.11 ± 0.13 ms/mmHg), but only for reflex bradycardia in hypertensive rats (-0.15 ± 0.02 vs -0.23 ± 0.3 ms/mmHg). In addition, the MAP and HR responses to the Bezold-Jarisch reflex were 20-30 percent smaller in amiodarone-treated normotensive or hypertensive rats. The bradycardic response to peripheral chemoreflex activation with intravenous potassium cyanide was also attenuated by amiodarone in both normotensive (-30 ± 6 vs -49 ± 8 bpm) and hypertensive rats (-34 ± 13 vs -42 ± 10 bpm). On the basis of the well-known electrophysiological effects of amiodarone, the sinus node might be the responsible for the attenuation of the cardiovascular reflexes found in the present study.

Morfologia da micrópila e da células micropilar em teleósteos neotropicais de água doce / Morphology of micropyle and micropylar cell in freshwater neotropical teleost

Através de análise ao microscópio de luz, caracterizaram-se quatro tipos de micrópilas em ovócitos vitelogênicos de 19 espécies de teleósteos, baseando-se na ocorrência e profundidade do vestíbulo, no comprimento do canal micropilar e na forma da célula micropilar. Em relaçäo a grupos taxonômicos, quatro espécies de pimelodídeos analisadas mostraram micrópila tipo 1, duas espécies de curimatídeos apresentaram micrópila tipo 2, nos caracídeos foram observados tipos 2, 3 e 4 e, nos anostomídeos, tipos 2 e 4. Os resultados indicam que a morfologia da micrópila e da célula micropilar variam em teleósteos de água doce, podendo apresentar padräo similar em alguns grupos sistemáticos