Differential effects of the orexin-1 receptor blockade in the prefrontal cortex and lesion of the lateral hypothalamus on neuronal activity in the orbitofrontal and anterior cingulate cortices

Background and Aim : Several studies indicate that orexins may take a part in the regulation of a difference form of affective and cognitive processes during wakefulness. The prefrontal cortex (PFC) plays a key role in cognitive processes. Orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC) as an important part of the PFC have a crucial role in reward and decision-making processes, and has a high density of orexin receptor type 1 (OX1Rs) in the PFC.Methods : In the present study, for detecting the role of the OX1Rson OFC neurons firing rate, the OX1Rswereinhibited in this area after 10-min baseline recording. In the second part of the study, the lateral hypothalamus (LH) as a main source of orexinergic neurons, was inhibited and its effect on the firing rate and activity pattern of the ACC or OFC neurons were detected by using single-unit recording technique in the rats.Results : Results showed that blockade of OX1Rs in the OFC could excite 8 neurons, inhibit 1 neuron and did not affect 2 neurons out of 11. Beside, the blockade of OX1Rs in the ACC could excite 6, inhibit 3 and did not affect 1neuron. Also, LH inactivation excited 5 out of 12 neurons and inhibited 6 neurons in the ACC. Also, it excited 8 and inhibited 6 neurons out of 14 neurons in the OFC.Conclusion : These data suggested that blockade of theOX1Rs excited 72% of the neurons but LH inactivation had an excitation effect just in 50% ofneurons in two main part of PFC regions. It seems that the PFC neurons receive the orexinergic inputs from the LH and indirectly from other sources.

Keywords:

Neuronal activity , Orexin-1 receptor , Lateral hypothalamus , Orbitofrontal cortex , Anterior cingulate cortex , Single-unit recording