Evaluation of the antinociceptive effects of gabapentin using Gromphadorhina portentosa as a non-vertebrate in vivo model

Gabapentin is a structural analogue of gamma-aminobutyric acid. Initially introduced as an anti-epileptic drug, it has also been shown to be effective in the treatment of pain in humans and non-human animals. The main purpose of this study was to test the suitability of the cockroach Gromphadorhina portentosa (Blattodea: Blaberidae) as a non-vertebrate in vivo model for evaluation of the antinociceptive properties of gabapentin. After the intersegmental abdominal membrane administration of different doses of gabapentin (50, 150 and 250 mg/kg), two acute thermal pain tests were performed: the hot plate test and the hot box escape test. In the hot plate test, 50 mg/kg gabapentin was the most potent dose in terms of reducing thermal stimulus-associated movement of the cockroaches; in the hot box escape test, 150 mg/kg gabapentin was the most efficacious dose. Thus, when comparing the two different tests, gabapentin exerted effective antinociception effects in cockroaches at different doses. This is similar to the effects observed in mice and rats exposed to thermal stimuli. Our results therefore demonstrate that G. portentosa could be a suitable non-vertebrate in vivo model for the study of pain, and suggest that it could be effectively used for the evaluation and screening of other analgesic compounds.