Anesthetic-dependent field potential interactions in the olfactory bulb.

The effect of anesthetic upon olfactory bulb field potentials evoked by paired stimuli to the lateral olfactory tract (LOT) was examined in male rats. Experiments were performed on rats anesthetized with urethane or barbiturates and on unanesthetized rats with midcollicular brain stem sections. Anesthetic doses of urethane (1.5 g/kg) produced an increse in the test response for condition-test intervals of 15-60 msec or more. With barbiturate anesthesia there was a decrease in the test response for all intershock intervals up to 150 msec. In unanesthetized rats with midbrain sections there was an increase in the test response with low intensity shock pairs and a decrease in the test response with high intensity shock pairs. Simultaneous use of both anesthetics produced either an increase or a decrease in the test response, depending upon the relative doses and upon the stimulus intensity. Paired stimuli to the olfactory nerve produced results similar to those with LOT stimulation. Augmentation of the olfactory bulb field potential produced by paired olfactory nerve shocks was not abolished by lesions which sectioned the LOT and produced extensive damage of the anterior olfactory nucleus.