Anesthesia protocol for ear surgery in Wistar rats (animal research).

OBJECTIVE: To formulate an anesthesia protocol for safe and satisfactory anesthesia for ear surgery in rats. METHODS: The rats were anesthetized with xylazine (10 mg/kg body weight) and ketamine at doses of 80, 50, 40, and 30 mg/kg body weight or with isoflurane anesthesia (2%-3.5% in 100% oxygen; maintenance dose 1.5%-3.5%). The anesthesia induction, surgery, and recovery time were recorded. RESULTS: In total, 17 rats were induced by varying doses of ketamine-xylazine and 28 rats with isoflurane. Mean induction time with ketamine-xylazine was 6 ± 2.9 min compared with 3.8 ± 1.1 min with isoflurane. Mean recovery time with ketamine-xylazine was 142.6 ± 49.3 min compared with 4.1 ± 1.2 min with isoflurane. A mortality of 4 animals after developing dyspnea was recorded with ketamine-xylazine. CONCLUSION: Isoflurane anesthesia offers appropriate induction and recovery times and low mortality rates for the surgeries performed. Isoflurane anesthesia offers reliable results for ear surgery in rats. However, more equipment and technical skills are needed.

Improved postauricular surgical approach to the round window of rats.

OBJECTIVES: Research using rat as an in-vivo model has played an important role in otological research. The rat ear anatomy has been described; however, detailed surgical procedures to access the temporal bone are limited. The authors present a technique to approach the inner ear of rat that was standardized by cadaveric dissections and later replicated in living animals. METHODS: Adult Wistar albino rats were dissected via the post-auricular approach. The emphasis was on early identification of the facial nerve that formed a reliable landmark for the tympanic bulla, which in turn houses the round window and stapedial artery. The point of identification of facial nerve was postero-inferior to the external auditory meatus. The procedure was then repeated in living animals. RESULTS: Seventeen cadaveric rats were dissected. Initially, the investigators attempted to identify the facial nerve at its crossing over the external auditory meatus. However, that method was found to be unsatisfactory. The facial nerve was then attempted to be identified in its course postero-inferior to the external auditory meatus. The technique improved drastically, and the facial nerve was identified promptly and reliably. The procedure was then repeated in seven living rats under general anaesthesia. The major issues encountered were bleeding from the stapedial artery, hematoma of the pinna in one rat. CONCLUSION: This study suggests that the post-auricular approach is a feasible and less time consuming route for round window drug delivery experiments in Wistar albino rats. Recognition of anatomical landmarks, particularly the facial nerve is the key to surgery.

Genistein represses PEPCK-C expression in an insulin-independent manner in HepG2 cells and in alloxan-induced diabetic mice.

Genistein has been reported to exert beneficial effects on type 2 diabetes mellitus (T2DM); however, the underlying molecular mechanisms involved therein have not been clearly elucidated. To address this question, the effect of genistein on the expression of phosphoenolpyruvate carboxykinase (PEPCK), and glucose production in HepG2 cells and in alloxan-induced diabetic mice was investigated. HepG2 cells were exposed to different concentration of genistein in presence or absence of modulators, and the expression of cytosolic PEPCK (PEPCK-C) and the signaling pathways was studied. Further, the biological relevance of the in vitro study was tested in alloxan-induced diabetic mice. Genistein lowered PEPCK-C expression and glucose production in HepG2 cells accompanied with increased in phosphorylation states of AMPK, MEK½, ERK½, and CRTC2. Treatment with the AMPK inhibitor (compound C) enhanced genistein-induced MEK½ and ERK½ activity indicating a potential cross-talk between the two signaling pathways. In vivo, genistein also reduced fasting glucose levels accompanied with reduced PEPCK-C expression and increased in AMPK and ERK½ phosphorylation states in the liver of genistein-treated alloxan-induced diabetic mice. Genistein fulfills the criteria of a suitable anti-diabetic agent by reducing glucose production and inhibiting PEPCK-C expression in HepG2 cells and also in alloxan-induced diabetic mice. These results indicate that genistein is an effective candidate for preventing T2DM through the modulation of AMPK-CRTC2 and MEK/ERK signaling pathways, which may allow a novel approach to modulate dysfunction in hepatic gluconeogenesis in T2DM.