Cardiovascular responses to microinjection of trans -(+)-ACPD into the NTS were similar in conscious and chloralose-anesthetized rats

The changes in mean arterial pressure (MAP) and heart rate (HR) in response to the activation of metabotropic receptors in the nucleus tractus solitarii (NTS) with trans-(+)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-(+)-ACPD) were evaluated in conscious and anesthetized Wistar, male rats weighing 240-260g (N=8). The responses obtained with trans-(+)-ACPD were compared with the responses to L-glutamate (1 nmol/100 nl), since in a previous study we showed that anesthesia converted a pressor response to L-glutamate microinjected into the NTS of conscious rats to a depressor response in the same rats under urethane or chloralose anesthesia. Microinjection of 3 doses of trans-(+)-ACPD (100, 500 and 1000 pmol/100 nl) produced a dose-dependent fall in MAP (range, -20 to -50 mmHg) and HR (range, -30 to -170 bpm) under both conscious and chloralose anesthesia conditions. These data indicate that the cardiovascular responses to the activation of metabotropic receptors by trans-(+)-ACPD are not affected by chloralose anesthesia while the cardiovascular responses to the activation of excitatory amino acid (EAA) receptors by L-glutamate are significantly altered.

Mecánica respiratoria del conejo bajo la acción del uretano, el pentobarbital o la mezcla cloralosa-uretano / Respiratory mechanics of the rabbit under the action of urethane, pentobarbital or chloralose-urethane mixture

Se caracterizó el patrón respiratorio dle conejo bajo la acción de 3 anestésicos. Se registraron el flujo y el volumen respiratorios mediante un neumotacógrafo, la presión intraesofágica y el electrocardiograma, en animales que respiraban espontáneamente en condiciones basales, agrupados y anestesiados como sigue: grupo 1: pentobarbital EV, 30 mg/kg; grupo 2: mezcla de uretano EV, 400 mg/kg y cloralosa EV, 60-80 mg/kg y grupo 3: uretano IP, 1,5 g/kg. Se analizaron las variables frecuencia respiratoria, volumen corriente, volumen minuto, flujo inspiratorio medio, relación entre tiempo de inspiración y tiempo total de la respiración (tiempo útil), resistencia pulmonar, complianza dinámica y frecuencia cardíaca. En el grupo 3 las variables indicadoras de la ventilación difirieron significativamente respecto a los grupos 1 y 2, que no mostraron diferencias entre sí. El tiempo útil fue diferente en los 3 grupos. En las demás variables no hubo diferencias significativas. Se valora que el uretano pueda ejercer una acción estimulante sobre la respiración

Influence of general anesthetics on baroreflex control of circulation

1. The effects of sodium pentabarbital and alfa-chloralose anesthesia on the barreflex control of ciruclation were studied in groups of 7 to 11 rats. The tests were performed in conscious undisturbed rats and repeated after anesthesia. 2. Pentobarbital (15 min) depressed the initial peak of the pressor response produced by carotid occlusion by 68% (15 ñ 1 vs 47 ñ 3 mmHg) and the mainteined rsponse by 52% (13 ñ 1 vs 27 ñ 4). Depression by chloralose was 48% (26 ñ 5 vs 50 ñ 3) and (19 ñ 2 vs 24 ñ 3), respectively. The inhibition progressively declined at 30, 60.90 and 120 min after pentobarbital but was unchanged up to 120 min after chloralose. 3. The baroreflex sensitivity index for bradycardic responses (phenylephrine injection) diminished by 50% after pentobarbital (-1.1 ñ 0.3 vs -2.2 ñ 0.3 beats/min per mmHg) and remained unaltered after chloralose. 4. The baroreflex sensitivity index for tachycardic responses (nitroprusside injection) was depressed by 61% after pentobarbital (-1.5 ñ 0.5 vs -3.8 - 0.5 beats/min per mmHg) and 35% after chloralose (-2.5 ñ 0.2 vs -3.9 ñ 0,5). 5. In general the depression of reflex control of ciruclation was more severe after pentobarbital than after chloralose anesthesia, while the resting control arterial pressurte was not affected by either. The inhibition of the baroreflex tachycardic responses was more intense than that of the bradycardic responses and represented a betther index of the depression exerted on the pressure responses to carotid occlusion