Isoflurane anesthesia is a valuable alternative for alpha-chloralose anesthesia in the forepaw stimulation model in rats.

Isoflurane (ISO) can be a valuable alternative for alpha-chloralose (ACL) anesthesia in functional MRI (fMRI) studies. Therefore, we compared the efficacy of the blood oxygen level dependent (BOLD) effect in fMRI studies during ISO and ACL anesthesia sequentially in the same animals. After non-invasive instrumentation for ventilation and monitoring, series of T2* weighted MR images were acquired during forepaw stimulation, first under ISO, then followed by ACL anesthesia. The results demonstrated that ISO and ACL were both suitable to perform this fMRI experiment. The center of activation was at the same stereotactic position for both anesthetics and matched the primary somatosensory cortex (S1). Under the applied conditions, the BOLD response during ISO anesthesia declined in magnitude during the first stimulation period, as compared to ACL. From this study, we conclude that since ISO has several positive properties in comparison to ACL, including fast pharmacokinetics and suitability for repeated measurements, it is a valuable alternative for anesthesia in fMRI studies of rats.

Suppression of noxious-induced c-fos expression in the rat lumbar spinal cord by isoflurane alone or combined with fentanyl.

BACKGROUND: Although our understanding of nociceptive processing during anesthesia has increased greatly over the last decade, many patients still experience hyperalgesia and acute pain postoperatively. The noxious-induced withdrawal reflex (NIWR) model is specifically designed and validated to quantitatively study the reaction on painful, multimodal stimuli in animals under anesthetic conditions. Since the anesthetic mechanisms differ between inhaled anesthetics and opioids, we evaluated the differential effects of isoflurane and fentanyl on c-fos expression at the lumbar level as a measure of nociceptive information transfer during general anesthesia. METHODS: The experimental setup consisted of a randomized block design with four experimental groups: two light (3/4) minimum alveolar concentration (MAC) isoflurane anesthesia groups (unstimulated/NIWR-stimulated) and two NIWR-stimulated surgical anesthesia groups (1(1/2) MAC isoflurane anesthesia and (3/4) MAC isoflurane anesthesia combined with fentanyl 400-600 microg x kg(-1) x h(-1)). After 2 h of intermittent electrical stimulation of the hind paw of the rat, the number of Fos immunoreactive (Fos-IR) neurons in the dorsal horn was measured quantitatively. RESULTS: The main suppressive effects on lumbar c-fos expression of isoflurane were observed in the superficial lamina II (P = 0.02), whereas fentanyl showed the strongest effects in lamina V (P = 0.05). CONCLUSIONS: This study demonstrates that the NIWR model combined with spinal Fos-immunoreactivity is a suitable and useful model for evaluating the differential effects of inhaled anesthetics and opioids on nociceptive information transfer during general anesthesia.

The Saanen goat as an animal model for post-laryngectomy research: practical implications.

A modern way of voice rehabilitation after total laryngectomy includes the use of shunt valves and tracheostoma valves. Problems of fixation to the surrounding tissue are a major drawback in the use of the shunt valve, heat and moisture exchange (HME) filters and, especially, the tracheostoma valve. To solve these problems different tissue connectors were developed. The main objective was to test the feasibility of these prototypes in a new animal model. Here we discuss the results, problems and complications of the selected Saanen goat model. In this prospective laboratory study, 19 healthy adult female Saanen goats (Capra hircus) were used and observed post-surgically for 12 weeks. Selection criteria such as comparable anatomy to humans and easy handling were used for animal model development. Also a literature search using the Medline and the ISI Web of Science databases was performed. The anatomy of the Saanen goat was investigated in a separate postmortem study. Surgery consisted of a laryngotracheal separation and implantation of a tracheo-oesophageal and tracheostoma tissue connector with fibrin tissue glue. Postoperative care consisted of frequent stoma care, monitoring appetite, weight, vital signs and administration of antibiotics, analgesics and mucolytic agents. All animals survived the surgical procedure. However, postoperative care was extensive, labour intensive and was accompanied by several complications. Eleven animals died spontaneously before the end of the experiment. The tracheostoma tissue connector caused signs of local infection in all cases. There was no evidence of infection around the tracheo-oesophageal tissue connector in 18 cases. It was concluded that the use of goats in this tracheostoma model was associated with major complications and should, therefore, only be used for short-term experiments with intensive care. Additional research is needed to see if clinical application of the tissue connectors is possible in the future.