Eider duck (Somateria mollissima) cerebellar neurons are highly tolerant toward
hypoxia in vitro, which in part is due to a
hypoxia-induced depression of their spontaneous activity. We have studied whether this response involves
ATP-sensitive
potassium (
KATP) channels, which are known to be involved in the hypoxic/ischemic defense of mammalian neural and muscular tissues, by causing hyperpolarization and reduced
ATP demand. Extracellular recordings in the Purkinje layer of isolated normoxic eider duck cerebellar slices showed that their spontaneous neuronal activity decreased significantly compared to in control slices when the
KATP channel opener
diazoxide (600 μM) was added (F1,70=92.781, p<0.001). Adding the
KATP channel blocker
tolbutamide (400 μM) 5 min prior to
diazoxide completely abolished its effect (F1,55=39.639, p<0.001), strongly suggesting that these drugs have a similar mode of action in this avian species as in mammals. The spontaneous activity of slices treated with
tolbutamide in combined
hypoxia/chemical
anoxia (95% N2-5% CO2 and 2 mM NaCN) was not significantly different from that of control slices (F1,203=0.071, p=0.791). Recovery from
hypoxia/
anoxia was, however, slightly but significantly weaker in
tolbutamide-treated slices than in control slices (F1,137=15.539, p<0.001). We conclude that
KATP channels are present in eider duck cerebellar neurons and are activated in
hypoxia/
anoxia, but that they do not play a key role in the protective shut-down response to
hypoxia/
anoxia.