SCN-independent circadian oscillators in the rat.

In this short overview, features of the two suprachiasmatic nucleus (SCN)-independent oscillators are described. One is restricted daily feeding (RF)-associated oscillator and the other is methamphetamine-dependent oscillator. We found that both oscillators have free-running period of circadian range, and express themselves in the special state of energy supply or energy deficiency. The expression of the RF-associated oscillator depends heavily on the catecholaminergic input from the medulla, whereas the methamphetamine-dependent oscillator appears to depend on the sympathomimetic effects of the drug. It is plausible that overt rhythms of both oscillators are complex, mainly because of the interaction of hourglass principle with circadian clock mechanism.