Abstract
The impacts of morphine and dexmedetomidine on the MAC of isoflurane were studied in rats constantly medicated with the cannabinoid WIN 55,212-2. METHODS: Prior to the administration of morphine, the MAC was measured in both untreated rats (MAC ((ISO))) and those treated with a cannabinoid (MAC ((ISO + CANN))). The effects of morphine (MAC ((ISO + MOR))) and dexmedetomidine (MAC ((ISO + DEX))) on untreated rats and rats treated for 21 days with the cannabinoids (MAC ((ISO + CANN + MOR))) and (MAC ((ISO + CANN + DEX)) were also studied. RESULTS: MAC ((ISO)) was 1.32 ± 0.06, and MAC ((ISO + CANN)) was 1.69 ± 0.09. MAC ((ISO + MOR)) was 0.97 ± 0.02 (26% less than MAC ((ISO))). MAC ((ISO + CANN + MOR)) was 1.55 ± 0.08 (8% less than MAC ((ISO + CANN))), MAC ((ISO + DEX)) was 0.68 ± 0.10 (48% less than MAC ((ISO))), and MAC ((ISO + CANN + DEX)) was 0.67 ± 0.08 (60% less than MAC ((ISO + CANN))). CONCLUSIONS: Medication with a cannabinoid for 21 days augmented the MAC of isoflurane. The sparing effect of morphine on isoflurane is lower in rats constantly medicated with a cannabinoid. The sparing effect of dexmedetomidine on the minimum alveolar concentration of isoflurane is greater in rats repeatedly medicated with a cannabinoid.