The use of sodium pentobarbital for the study of immobility-related (type 2) hippocampal theta

A series of experiments investigated the effects of sodium pentobarbital on the dentate electroencephalographic (EEG) activity of rats and rabbits implanted with tungsten microelectrodes. Type 1 (movement-related) theta was abolished in both species and Type 2 (immobility-related) theta was abolished in the rat but remained intact and readily elicitable by sensory stimulation in the rabbit, following anaesthetic doses of pentobarbital. It was proposed that sodium pentobarbital may be useful for the investigation of mechanisms underlying the two types of theta and that the effect of pentobarbital provides further evidence for species differences in the way the hippocampal formation produces Type 2 theta.