A study of the effects of clonidine on the EEG in rats treated with single and multiple doses of antidepressants.

The influence of repeated and single administrations of desipramine, amitryptiline, and mianserin on the EEG effects of clonidine has been investigated in rats implanted with chronic cortical electrodes. Clonidine induced a dose-dependent EEG synchronization in control animals. Signs of behavioral depression occurred after administration of moderate (0.1 mg/kg) and higher (0.2 mg/kg) doses of clonidine. Single doses of desipramine and amitryptiline attenuated the clonidine effect, while mianserine potentiated clonidine-induced synchronization. Antidepressants given once daily for 14 days completely (desipramine and amitryptiline) or partially (mianserin) reduced the effect of clonidine. Antidepressants alone produced only a slight effect on cortical EEG pattern.

Differential clonidine effects on EEG following lesions of the dorsal and median raphe nuclei in rats.

The effects of clonidine on EEG activity and gross behavior were studied in rats with electrolytic lesions of the median (MR) and dorsal (DR) raphe nuclei. Lesioned animals showed significant depletion in forebrain serotonin concentrations. Clonidine (0.1 mg/kg and 0.2 mg/kg IP) produced synchronization in cortical EEG pattern and markedly increased alpha and theta activities in unlesioned animals. Clonidine treatment resulted also in a sedative response. In MR lesioned rats clonidine effect upon EEG was significantly reduced and, additionally, sedative response was not seen. On the other hand clonidine effect on EEG was markedly increased in rats with lesioned DR. These results are discussed on the basis of possible interaction between serotonergic and noradrenergic neurons in the brain.