To learn whether the low flux density combined magnetic field (CMF) can affect rats pretreated with a dopamine agonist, the frequency spectra of cortical and hippocampal EEG were studied after intraperitoneal injection of agroclavine (50 microg/kg, Day 1) either alone (N=5) or combined with 30-min exposure to CMF (B(AC)=50 microT, f(AC)=20.9Hz, B(DC)=27.3 microT) (N=5) an hour post-injection. The CMF caused an immediate and robust increase in the hippocampal beta(2) activity (22.5-30.5Hz) vs. its value in the pre-exposure period. This effect persisted during 30-min post-exposure period. After vehicle injection (0.1% ethanol) on Day 10, the beta(2) activity increased gradually during the exposure to CMF and was at the pre-exposure level during the post-exposure period. In two rats, pretreated with the vehicle on Day 1, CMF increased a hippocampal beta(2) level. The effect was about half the amplitude and shorter in duration than that after agroclavine, with no effects in the post-exposure period. However, during the 2nd exposure to CMF, started 30 min later, cortical and hippocampal beta activity was significantly greater than that during the 1st. On Day 10, the 1st exposure was completely ineffective, while during the 2nd, the hippocampal beta(2) activity was increased gradually. These results demonstrate that dopaminergic activation can potentiate CMF-evoked EEG effects in the hippocampal beta(2) frequency band.