A sudden physical change in the sequence of standard auditory stimuli elicits, in humans, an event-related potential (ERP) called mismatch negativity (MMN) (Näätänen 1992). A MMN-like response has also been recorded epidurally above the auditory cortex (AC) in anesthetized rats (Ruusuvirta et al. 1998). Evidence obtained in monkeys suggests that N-methyl-D-aspartate (NMDA) receptor antagonists affect the generation of the MMN (Javitt et al. 1996). We aimed to investigate the effects of an NMDA receptor antagonist MK-801 (dizocilpine, Germany) on auditory ERPs recorded epidurally above AC in anesthetized rats during an oddball (OB) paradigm. Two tones of different frequencies were used as stimuli in the OB paradigm (randomized 96% standards and 4% deviants). Either saline or a low (0.1 mg/kg) or a high dose (0.3 mg/kg) of MK-801 was injected intraperitoneally before the recording. During OB paradigm in saline condition, a MMN-like response was recorded within a time interval of 60-190 ms after the presentation of the deviant tone. The NMDA receptor antagonist dose-dependently blocked the generation of the MMN-like component. These results suggest that the MMN-like potential that is recordable in rats during an OB paradigm is dependent on an intact NMDA receptor system.

REFERENCES

Javitt, D.C., Steinschneider, M., Schroeder, C.E. & Arezzo, J.C. 1996. Proc Natl Acad Sci USA 93, 11962-11967.

Näätänen, R. 1992. Attention and Brain Function. Erlbaum. New Jersey.

Ruusuvirta, T., Penttonen, M., Korhonen, T. 1998. Neurosci Lett 248, 45-48.