Ethanol withdrawal tremor does not interact with physostigmine-induced tremor in rat

Tremor in rats withdrawn from repeated ethanol administration was analyzed using an electronic device. The ethanol withdrawal tremor appeared in bursts during the first and second day of withdrawal and subsided at the third day of withdrawal. The frequency analysis showed that the mean frequency of withdrawal tremor was 6-7 Hz during the 48 hr observation period used. The frequency spectra of tremor induced by physostigmine (0.7 or 0.9 mg/kg) in control rats revealed that the tremoring frequency encompassed only a narrow peak, which temporarily decreased from 13 Hz to 11 Hz during the tremoring period. Arecoline (25 mg/kg) also induced tremor with a peak frequency at 13 Hz, but this tremor did not show any temporary decrease in peak frequency. The frequency analysis of tremor in ethanol withdrawn rats treated with physostigmine showed that the rats trembled at two frequencies, 6-7 Hz and 13 Hz. These two frequencies, each characteristic for one of the treatments, remained separate during the 48 hr observation period. As these two tremors did not interact with each other, it is suggested that these tremors are mediated by different mechanisms in the central nervous system. Thus it seems unlikely that the central muscarinic cholinergic system is involved in the genesis of tremor during ethanol withdrawal.