the modulatory effects of orexin b on the calcium channels activity in neuronal cells of helix aspersa (garden snail)

introduction: the functional effects of orexin-b on the calcium spikes and excitability of the neuronal soma membrane of garden snail, helix aspersa were studied. methods: conventional intracellular recording, under the current clamp conditions was performed to examine the effects of orexin-b on the configuration and electrophysiological properties of calcium spikes. results: application of orexin-b (300 nm) led to a membrane depolarization and thereby the increase in excitability of neurons. it also decreased the duration and the amplitude of calcium spikes. on the other hand, orexin-b had a dual effect on the amplitude of afterhyper polarization (ahp) in a time dependent manner. the maximum reduction of the amplitude of ahp was recorded within 10 min of orexin-b exposure. however a maximum increase in ahp amplitude was observed later (15 min after exposure to orexin-b). inactivation of g-proteins by pertussis toxin (100 nm) was used to test the involvement of gi/go in the orexin-b induced modulation of calcium channels. pre-incubation of ganglia for 3-6 h with ptx blocked the depolarization effect of orexin-b on the resting membrane potential. orexin-b on pretreated neuronal cells with ptx did not statistically change the calcium spike parameters, unless the peak amplitude of ahp increased remarkably. conclusion: in conclusion, these data suggest that orexin-b (300 nm) may affect the membrane excitability and modulates the activity of calcium and calcium activated potassium channels in snail neurons.