Short-term lithium administration enhances serotonergic neurotransmission: electrophysiological evidence in the rat CNS.
Rats received lithium-containing chow for 48 h. Brain and plasma lithium concentrations ranged from 0.4 to 1.0 mEq/l. A first series of experiments served to assess the responsiveness of CA3 hippocampal pyramidal neurons to microiontophoretically applied serotonin (5-HT) and norepinephrine (NE). The response of the same neurons to electrical stimulation of the ventro-medial 5-HT pathway was measured after lithium treatment. The responsiveness to 5-HT and NE was not modified whereas the effect of activation of the ascending 5-HT pathway was increased two-fold by the lithium treatment. These neurons were activated to their physiological firing rate by means of small ejection currents of acetylcholine. A pretreatment with the 5-HT neurotoxin 5,7-dihydroxytryptamine abolished the response to the electrical stimulation in lithium-treated rats. In a second series of experiments, unitary recordings of 5-HT neurons were obtained from the dorsal raphe nucleus. The lithium treatment modified neither the number of spontaneously active 5-HT neurons nor their mean firing rate. These results provide direct electrophysiological evidence for the enhancement of 5-HT neurotransmission by short-term lithium treatment through its presynaptic action on 5-HT terminals.
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects*; D004558:Electric Stimulation; D006624:Hippocampus / Q000187:drug effects; D008094:Lithium / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009434:Neural Pathways / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism; D011903:Raphe Nuclei / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*
D011985:Receptors, Serotonin; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D008094:Lithium; D009638:Norepinephrine