Inhibitory effect of orexin-A on GABAergic synaptic transmission in rat locus coeruleus neurons

The locus coeruleus (LC) contains large clusters of noradrenergic neurons which project widely throughout the central nervous system including hypothalamus. The LC is involved in cognitive processes, including attention, learning, memory and drug addiction. Orexin neuropeptides excite the noradrenergic LC neurons; however, its effects on inhibitory synaptic transmission to the LC neurons are unknown.
Here, we investigated the effect of orexin-A (100 nM) on sIPSCs in LC neurons. We used whole-cell patch clamp recording in rat horizontal slices containing the LC nucleus.
Our electrophysiological data indicate that orexin-A application only decreased sIPSCs frequency of LC neurons that was blocked by SB-334867, selective orexin type-1 receptors.
In this study, our findings suggest that orexin-A depresses sIPSCs frequency through orexin type-1 receptors. It can be deduced that these changes in inhibitory synaptic transmission may be elicited by prestsynaptic mechanism. These results provide in vitro evidence for a critical role of orexin signaling in LC neurons.