Delayed behavioral effects of SH-I-048A, a novel nonselective positive modulator of GABAA receptors, after peripheral nerve injury in rats

Abstract

The complex clinical picture of mono-neuropathy following injury of peripheral nerve is often accompanied by changes in the patients' affective states. It has been shown that positive allosteric modulators of GABAA receptors can decrease nociceptive transmission in animal pain models. However, recent findings suggest a possibility that at least some of the antinociceptive effects of benzodiazepines, related to neuropathic painful stimuli, may to a significant degree be a consequence of their anxiolytic action. In this study we evaluated the possible delayed effects of SH-I-048A, a newly- synthesized high-efficacy nonselective positive modulator of GABAA receptors, on anxiety-like behavior and locomotor activity in Wistar rats with a previously induced peripheral nerve injury. Assessment of behavioral parameters, using spontaneous locomotor activity and elevated plus maze tests, was performed 48h after completion of single-day three i.p. injections treatment consisting of zero, one, two or three doses of SH-I-048A (10 mg/kg). In general, rats' behavior observed 72 h after a moderate peripheral nerve injury did not indicate the persistence of sequelae of mono-neuropathic pain. The rats treated with three doses of SH-I-048A displayed an enhanced immobility time in the locomotor activity test, without concomitant decrease of the total distance traveled. On the other hand, in the group treated with two doses of SH-I-048A, a decrease in the emotional reactivity in the elevated plus maze test was observed. Subtle changes in the regimen of dosing of SH-I-048A affect locomotor activity and anxiety-related behavior in animals with peripheral nerve injury.

Kompleksna klinička slika neuropatije nakon povrede perifernog nerva često je praćena i promenama afektivnog stanja pacijenata. U animalnim modelima bola pokazano je da pozitivni alosterni modulatori GABAA receptora mogu da smanje nociceptivnu transmisiju. Međutim, skorašnji nalazi ukazuju i na mogućnost da je prividni antinociceptivni efekat benzodiazepina nakon delovanja akutnog bolnog stimulusa u značajnoj meri posledica anksiolitičnog efekta. U ovoj studiji ispitani su mogući odloženi efekti novosintetisanog, neselektivnog liganda GABAA receptora (SH-I-048A) na lokomotornu aktivnost i ponašanje u vezi sa anksioznošću kod pacova soja Wistar prethodno podvrgnutih povredi perifernog nerva. Procena bihejvioralnih parametara sprovedena je testovima spontane lokomotorne aktivnosti i uzdignutog plus lavirinta 48 sati nakon što su životinje u periodu od 24 sata primile rastvarač, jednu, dve ili tri doze SH-I-048A (10 mg/kg). Generalno, ponašanje pacova praćeno 72 sata nakon umerene povrede perifernog nerva nije ukazivalo na prisustvo perzistentnih posledica neuropatskog bola. Pacovi prethodno tretirani sa tri doze SH-I-048A ispoljili su povećano vreme imobilnosti u testu lokomotorne aktivnosti, bez značajnog smanjenja ukupnog pređenog puta. S druge strane, u grupi koja je tretirana sa dve doze SH-I-048A zapažena je smanjena emocionalna reaktivnost u uzdignutom plus lavirintu. Kod životinja sa povredom perifernog nerva, suptilne razlike u režimu doziranja pozitivnog modulatora GABAA, mogu značajno da utiču na ponašanje vezano za lomotornu aktivnost i nivo anksioznosti.