α-Pinene Influence on Pulpal Pain-Induced Learning and Memory Impairment in Rats Via Modulation of the GABAA Receptor.

ABSTRACT

Background: This study investigated the effect of central administration of α-pinene and the interaction of α-pinene with GABAA receptor on pulpal nociception-induced changes in learning and memory performances in rats. Materials and Methods: Sixty-six adult male Wistar rats were used. Pulpal nociception was induced by intradental application of capsaicin (100 µg/rat). α-pinene (0.1, 0.2, and 0.4 µg/rat) was injected centrally 10 min before the administration of capsaicin. In addition, α-pinene (0.4 µg/rat) was co-injected with bicuculline (0.5 µg/rat). Spatial and passive avoidance learning and memory were assessed using Morris water maze (MWM) and shuttle box tasks, respectively. Results: Experimental results of the MWM test showed that capsaicin increases escape latency and distance traveled to the hidden platform (P < 0.01). The effect was prohibited by α-pinene at the dose of 0.4 µg/rat. Moreover, capsaicin-treated animals spent less time in the target zone than capsaicin + α-pinene (0.4 µg/rat)-treated rats (P < 0.05). In the shuttle box test, α-pinene (0.2 µg and 0.4 µg) prevented an increased number of acquisition trials and time spent in the dark chamber induced by capsaicin, whereas it increased step-through latency (P < 0.01). However, the effects of α-pinene (0.4 µg/rat) in both tests were prohibited by bicuculline (0.5 µg/rat). Conclusion: The data showed that central administration of α-pinene might reduce pulpalgia-induced learning and memory impairment, at least partially, via modulation of GABAA receptors.