Spontaneous activity of olfactory bulb neurons in awake rabbits, with some observations on the effects of pentobarbital anaesthesia.

A specially adapted microelectrode driver device has been used to record the spontaneous activity of neurons in the olfactory bulb of awake rabbits. Several parameters of this activity were studied in 78 neurons of conscious animals. A second experiment was performed to investigate anaesthetic-induced modifications of the spike discharge initially recorded in awake animals. 1. In unanaesthetized animals, the interspike interval distribution of all cells was found to be stable over short as well as long periods of time. 2. A periodical change in firing probability, correlated with respiratory activity, was observed in a high percentage of neurons. During inspiration, the discharge was markedly increased ("well synchronized" neurons, n = 2), slightly increased ("poorly synchronized" neurons, n = 15); or unchanged ("not synchronized" neurons, n = 8). 3. The passage from the awake to the anaesthetized state resulted in more regular cell activity with sudden changes from one steady firing level to another, without affecting the cell classification. As anaesthesia wore off, the cell units recovered the characteristic discharge pattern initially observed.