[Slow potentials of the olfactory bulb in the carp]

The slow negative potentials evoked in carp olfactory bulb (OB) by some odorants and slow positive potentials evoked by nonspecific irritation (water stream, NaCl solutions) of olfactory epithelium have been studied. The slow potentials of both types were not inverted in deep layers of OB and were resistant to blockade of synaptic transmission by manganese ions. The negative slow potentials were not also affected by hypoxia and associated with local increase of OB tissue resistance. Positive slow potentials were affected by hypoxia and associated with local decrease of OB tissue resistance. The electrical tetanization of local zones of olfactory epithelium evoked in OB steady potential shifts of negative polarity, but diffuse tetanization of olfactory nerve evoked shifts of positive polarity. The results support the hypothesis of glial origin of slow potentials. Possible mechanisms of slow negative and positive potential generation are discussed.