Comparing the Effect of Methods of Rat Euthanasia on the Brain of Wistar Rats: Cervical Dislocation, Chloroform Inhalation, Diethyl Ether Inhalation and Formalin Inhalation

Contentions still exist as to the most humane method of sacrificing experimental animals. Beyond humaneness, there is also the issue of appropriateness of a method of sacrifice with regards to organ safety. This study compared four common methods of rodent sacrifice used in Nigeria and their effects on the brain. Twenty male Wistar rats weighing 150 to 180g were randomly separated into four groups of five rats each. After a two week period of acclimatization,the animals were sacrificed; Group A by Cervical dislocation (CD) which also served as control, Group B by chloroform inhalation (CI), Group C by diethyl ether inhalation (DEI) and group D by Formalin inhalation (FI). The time taken for the animals to pass out was documented and the brains were harvested. Four of the brains from rats in each group were homogenized in phosphate buffer solution and centrifuged at 10000rpm. The supernatant were used for antioxidant studies. The remaining one brain from each group were fixed in 10% formal saline and after 48 hours, the cerebellum (CB) and hippocampus (Hp) were used for histological studies using the H & E method. Our results show although CD was the quickest, it gave the least quantity of blood. Meanwhile CI was the most humane, gave the most blood and saved time compared to DEI and FI. None of the methods of sacrifice showed adverse effect on the antioxidant parameters of the rats. However, histological studies showed that while CD and CI showed no adverse effects on the hippocampus, only CD was completely safe for the CB. The other methods showed various levels of cell death. It is therefore expedient to consider these factors in making the choice of an appropriate method of sacrifice and to use the most humane and safest method with reference to the organ studied

Anestesia de roedores sigmodontinos en condiciones de campo / Anesthesia in Sigmodontinae Rodents Living out in the Countryside

Resumen Algunas investigaciones de mamíferos silvestres requieren del uso de métodos que faciliten la manipulación de los individuos en condiciones de campo, sin afectar negativamente a los animales o a los investigadores. Dentro de estos métodos, se encuentra la inmovilización química, la cual no ha sido muy documentada en roedores silvestres de la subfamilia Sigmodontinae (Cricetidae). Por ello, en esta investigación se evaluó el uso de éter dietílico inhalado para manipular roedores sigmodontinos en campo, comparando el tiempo de inducción y el tiempo de recuperación de la anestesia entre especies, sexos y tipos de ambientes. Se capturaron y anestesiaron un total de 289 individuos de seis especies en el Parque Nacional Natural Chingaza. El tiempo de inducción de la anestesia fue diferente entre Microryzomys minutus, Neomicroxus bogotensis, Thomasomys laniger y Thomasomys niveipes (F3; 552 = 9,36; p < 0,05); de igual forma, el tiempo de recuperación de la anestesia fue diferente entre dichas especies (H = 9,59; p = 0,022). No se encontraron diferencias en los tiempos de inducción y recuperación de la anestesia entre sexos, ni entre ambientes. La mortalidad total fue de 4,5 %. No se observaron secreciones mucosas, vómito o complicaciones cardíacas o respiratorias en los individuos anestesiados. Los individuos fueron recapturados y no se evidenciaron alteraciones en su comportamiento o aspecto físico que indicaran una afectación por la anestesia o manipulación en capturas previas. La anestesia inhalada con éter dietílico puede ser una opción rápida y segura para inmovilizar y manipular sigmodontinos durante procedimientos cortos en campo dentro de estudios poblacionales o programas de monitoreo en vida silvestre.

Abstract Some researches in wild mammals require methods that enable to handle the animals living in wild conditions, without affecting negatively the animals, or the researchers. These methods include the chemical immobilization, which has not been enough documented when handling wild rodents of the Sigmodontinae subfamily (Cricetidae). Therefore, this research evaluated the use of diethyl ether when handling Sigmodontinae rodents out in the countryside. It compared the induction time to the anesthesia recovery time between species, genders, and type of environments. A total of 289 animals were caught and anesthetized from six species in the Chingaza National Natural Park. The anesthesia induction times were different between Microryzomys minutus, Neomicroxus bogotensis, Thomasomys laniger y Thomasomys niveipes (F3; 552 = 9.36; p < 0.05). Likewise, the anesthesia recovery times were different between the same species (H = 9.59; p = 0.022). No difference was found in the induction times and the anesthesia recovery times between genders, neither for the types of environment. Total mortality was 4.5%. None mucosal secretions, vomit, or cardiac/respiratory complications were observed in the anesthetized animals. These subjects were caught again and they did not show any alterations in their behavior or physical aspect indicating affection derived either from the anesthesia or the previous handling under captivation. Anesthesia with diethyl ether can be a quick and safe choice when it comes to immobilize and handle Sigmodontinae rodents during short procedures out in the countryside, when carrying out population studies or wildlife monitoring programs.

Antihypertensive Effects of Nasal Administration of Nifedipine in Patients Anesthetized with Diethyl - Ether / 대한마취과학회지

The effect of intranasal nifedipine drops in 20 randomly chosen patients with diethyl-ether induced hypertension by inhalation anesthesia was observed. Patients were placed in two groups: the first group received intranasal nifedipine at the time of induction and the second group received intranasal nifedipine at the time to skin incision. The change in mean arterial pressure in the first group was not significant, but in the second group, the increase in mean arterial pressure was significant immediately after intranasal administration of nifedipine at the time of skin incision. An increase in pulse rate was noted with the increase in mean arterial pressure and this is thought to result from the stimulation of catecholamine secretion and baroreceptor reflex. Since the difference in mean arterial pressure between the two groups was minimal at ten minutes and twenty minutes after skin incision, it is suggested that the onset of intranasal nifedipine is quite fast. Based on the authors' experience, intranasal administration of nifedipine is very useful in preventing or treating hypertension during inhalation anesthesia using diethyl-ether.