Validating injectable anesthesia for the streptozotocin-induced diabetic retinopathy rat model

Abstract

Purpose : Streptozotocin (STZ) induced hyperglycemic rats, commonly used in preclinical diabetic retinopathy (DR) research, have poor response to the most used laboratory rodent anesthesia such as medetomidine/ketamine mixture (MK), and are prone to develop various welfare issues. The purpose of this study was to compare medetomidine/midazolam/butorphanol anesthesia (MMB) to MK in the STZ induced DR rat model to validate injectable anesthesia with less side effects and faster recovery time without compromising the DR development.

Methods : Two groups (n=14/group) of 8-week-old RjHan:SD rats (Janvier Labs), were induced with two IP injections of STZ (32 mg/kg, Sigma Aldrich) in sodium citrate buffer. Two additional groups of rats (n=11/group) were injected with buffer (sham). The DR pathology was evaluated at Week 4, 6, 8, and 14 with flash electroretinography (ERG) and retinal thickness measurement by Spectral-Domain Optical Coherence Tomography (SD-OCT). Rats were anesthetized for the procedures with either MMB (0.15, 2, 2.5 mg/kg) or MK (0.3, 40 mg/kg). MMB was reversed with a mixture of atipamezole, flumazenil, and naloxone (0.75, 0.2, 0.12 mg/kg), and MK was reversed with atipamezole (1 mg/kg). Clinical health scoring (body weight, grimace, porphyrin excretion) was performed 24h after anesthesia.

Results : Clinical health scoring indicated better body weight maintenance and lower distress levels in MMB groups compared to the MK groups. At Week 14 the blood glucose levels were 5.8±0.5 (sham+MMB), 5.7±0.7 (sham+MK), 27.7±6.7 (STZ+MMB), and 29.6±7.0 (STZ+MK) mmol/l. The STZ induced rats anaesthetized at Week 14 with MMB showed a significant reduction in the flash ERG b-wave amplitude at 1, 3, and 10 cd.s/m² luminance (Fig.1.). A similar trend was seen with the main OPs.

Conclusions : The development of the DR phenotype was not affected by the anesthetics. MMB proved suitable injectable anesthesia for STZ-induced hyperglycemic rats in the DR research, having fast recovery, and less adverse effects on animal welfare.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Fig. 1. B-wave amplitude for the 1, 3 and 10 cd.s/m² luminance. The b-wave amplitude was significantly decreased in the STZ+MMB group compared to the sham with all the luminance tests (P=0.002, P=0.042, P=0.042, respectively, one-way ANOVA). Data are presented as mean±SD from 11–14 rats per group. Group differences were analyzed by Tukey’s multiple comparison test. *, P<0.05; **, P<0.01.