Orexin/hypocretin excites the histaminergic neurons of the tuberomammillary nucleus - PubMed (original) (raw)

Characterization of the mechanism of depolarization. In A, the effects of different treatments on the depolarization induced by 300 n

m

orexin-A are summarized. Increasing the external K+concentration had no significant effect on the response. Replacing most of the external Na+ with NMDG+ resulted in efficient blocking, indicating dependency on external Na+. The selective NCX blocker KB-R7943 (80 μ

m

) also strongly suppressed the depolarization. Treatment with 3 m

m

NiCl2 blocked the depolarization almost completely. In the top tracing in_B_, the voltage recording shows a representative depolarization of a TM neuron by 300 n

m

orexin-A. In the_middle tracing_ the slice has been preincubated with the NCX blocker KB-R7943 (80 μ

m

). The depolarization is smaller, delayed by almost 2 min, and develops more slowly compared with the control. In the bottom tracing the effect of 3 m

m

NiCl2 is shown. Ni2+causes a transient hyperpolarization by itself and completely inhibits the effect of 300 n

m

orexin-A. In C, the effects on the orexin-B-induced depolarization by 3 m

m

NiCl2 and 80 μ

m

KB-R7943 are demonstrated. Treatment with KB-R7943 attenuates the depolarization, and Ni2+ has a very strong inhibitory effect.Numbers above bars indicate_n_. **p < 0.001; *p < 0.05.