Reza Fartootzadeh - Department of Physiology, Ramsar Campus, Mazandaran University of Medical Sciences, Ramsar, Iran
Ramezan Taheri - Nanobiotechnology Research Centre, Baqiyatallah University of Medical Sciences, Tehran, Iran
Mohammad Reza Nourani - Nanobiotechnology Research Centre, Baqiyatallah University of Medical Sciences, Tehran, Iran
Kamelya Goudarzi - Department of Psychiatry, Ramsar Campus, Mazandaran University of Medical Sciences, Ramsar, Iran

Objective(s): Long-term potentiation (LTP) is a kind of synaptic plasticity and has a key role in learning and memory. Endocannabinoids and orexins are the endogenous systems that can modulate synaptic plasticity. Given that new studies have shown an interaction between cannabinoid and orexin systems in the brain, we decided to examine this interaction between the two systems on LTP induction in rat’s hippocampus.Materials and Methods: Twenty-eight male Wistar rats were used for evaluating the effects of co-administrating of cannabinoid-۱ receptor (CB۱R) antagonist (AM۲۵۱) and orexin-۲ receptor (OX۲R) antagonist (TCS OX۲ ۲۹) on the induction of LTP in the Schaffer collateral-CA۱ synapses of rat hippocampus. The drugs were microinjected into the CA۱ area of rat hippocampus ۳۰ min before inducing of LTP.Results: Results showed that sole administration of the antagonists inhibited LTP, with respect to the control group. Also, co-administrating of them reduced LTP as compared to the control group, but not significantly more than that when the antagonists were solely microinjected into the CA۱. Nonetheless, the inhibitory effect of concurrent administration of the antagonists on LTP lasted until the end of the recording. Conclusion: These results propose that endogenous cannabinoids and orexins play a role in the expression of LTP, at least by CA۱-CB۱Rs and CA۱-OX۲Rs, respectively. Finally, there is no interaction between CB۱R and OX۲R on the induction of LTP in the Schaffer collateral-CA۱ synapses; therefore, these two systems possibly act through common signaling pathways in the hippocampus’s CA۱ region.

AM۲۵۱, Cannabinoid receptors, Hippocampus, Long-term potentiation, Orexin receptors, TCS OX۲ ۲۹