The role of hyperpolarization-activated non-selective cation current in amygdala excitability and serotonin mediated effects.

The hyperpolarization-activated, cyclic nucleotide-dependent non-selective cationic (HCN) current (Ih) has an important functional role in the rat brain, participating in network oscillations, temporal summation of synaptic inputs, and seizure development. Since hyperexcitability of the amygdala is related to anxiety and stress disorders, we investigated the role of Ih in amgydala excitability. In lateral amygdala (LA) pyramidal neurons, blockade of Ih reduced the degree of spiking accommodation, suggesting that Ih modulates amygdala excitability. Since serotonin (5-HT) has a significant role in fear and anxiety disorders, we additionally investigated the modulatory effect of 5-HT on Ih in LA neurons. The results show that 5-HT can reduce Ih¬, possibly through activation of 5-HT2 receptors. Overall, the results suggest that Ih may be an important new target for pharmacological treatment of psychiatric disorders involving the amygdala.