Search

Rats pretreated with lithium or sodium chloride were killed at various intervals and the forebrains analyzed for 5-HT and 5-HIAA. Pretreatment of rats with lithium chloride increased the rate of brain serotonin turnover. This effect of lithium was accentuated by electrical stimulation of serotonincontaining neuronal perikarya in the dorsal raphe nucleus.

The action of different doses of LSD on shock elicited fighting was tested in rats. A biphasic dose response was found with low doses facilitating fighting whereas a high dose had no effect. The results are discussed in terms of the effects of LSD on single units of the serotonin neuronal system.

The early positive cortical evoked potential to somatosensory stimuli is regularly increased in amplitude in patients receiving lithium carbonate treatment. This may reflect a unique neurochemical effect of lithium since similar changes have not been observed in humans following other drugs. To investigate this finding, cortical evoked potentials to peripheral somatosensory stimulation were obtained in rats and cats with implanted epidural electrodes. In rats, increasing doses of oral lithium chloride, up to 5 meq/kg/d which approached the LD 50, produced no reliable change in the early positive evoked response amplitude. In cats, an increased amplitude of the early positive-negative cortical potential was observed in every instance and the serum lithium levels were within the range used clinically in humans. The increased cortical evoked response amplitude in cats did not directly correlate with serum lithium levels but was delayed 1 to 5 days after serum lithium levels reached their peak. The findings in cats are similar to the human studies. The negative results observed in rats may reflect important species differences regarding lithium.

Awake, unrestrained rats were stimulated electrically via chronic electrodes implanted in the region of serotonin-containing neurones in the midbrain raphe. Behavioral observations showed a failure of the usual habituation to reptitive sensory stimuli (as indicated by a persistence of the startle response) without any evidence of motor excitation, or somnolence. Para-chlorophenylalanine and reserpine abolish this effect of raphe stimulation. Rental temperatures showed a rise of 1 – 1.5°C during the course of stimulation.