EFFECTS OF NEUROTENSIN AN EEG AND EVENT-RELATED POTENTIALS IN THE RAT

Neurotensin has neuromodulatory actions on multiple brain functions in cluding motor, sensory and limbic processes. However, little is known about how neurotensin affects general arousal and/or attention states. The present study evaluated the effects of neurotensin on spontaneous brain activity as well as auditory evoked responses using electrophys iological measures. Electroencephalographic and event-related potentia l recordings were obtained in awake animals following intracerebrovent ricular administration of neurotensin (1.0, 10.0 and 30.0 mu g). Twent y rats were implanted with recording electrodes in the frontal cortex, dorsal hippocampus, amygdala and nucleus accumbens. Neurotensin was f ound to produce a dose-related effect on behavior and electrophysiolog ical measures. Lower doses (10 mu g) produced no obvious behavioral ch anges, but significantly reduced EEG power in the lower frequency rang es (2-6 Hz) in the frontal cortex, the anterior amygdaloid complex and the nucleus accumbens. At higher doses (30 mu g), rats appeared behav iorally inactivated, and EEG power was reduced in all structures in bo th the lower frequency ranges (2-6 Hz) and the higher frequency ranges (8-32 Hz). Auditory processing, as assessed by event-related potentia ls, was affected most significantly in amygdala and dorsal hippocampus . In the amygdala, the amplitude of the P3 component of the auditory e vent-related potential was increased significantly by doses of 10.0 an d 30.0 mu g. In the dorsal hippocampus, the amplitude and the area of the N1 component was increased dose dependently and significance was r eached at the 30 mu g dose. These electrophysiological findings indica te that neurotensin does not reduce the arousal level of the animals a nd in fact may enhance neurosensory processing in limbic areas through increased arousal and/or enhanced stimulus evaluation.