Effects of lithium treatment on extracellular serotonin levels in the dorsal hippocampus and wet-dog shakes in the rat

In the present study wet-dog shakes in rats were induced by local potassium (K+) depolarization in the dorsal hippocampus. Concurrently, changes in ex tracellular concentrations of cyclic AMP (cAMP) and serotonin (5-HT) were a ssessed by microdialysis. It has been well-established that lithium influen ces the synthesis of cAMP in the brain via effects on adenylate cyclases. I n this study, the effect of chronic lithium treatment on the number of wet- dog shakes and the release of 5-HT was investigated. Wet-dog shakes, format ion of cAMP and release of 5-HT were induced by perfusing a Ringer solution containing 60 mM K+ through the microdialysis probe for 20 min. Under some conditions, this high K+ solution also contained 20 mu M forskolin. The nu mber of wet-dog shakes and the formation of cAMP induced by K+ depolarizati on were enhanced by forskolin, while the K+-stimulated release of 5-HT was unaffected by forskolin. Chronic lithium treatment, yielding a plasma lithi um level of 0.78+/-0.09 mmol/l, decreased the number of wet-dog shakes but did not affect the extracellular level of 5-HT in the dorsal hippocampus. C hronic lithium treatment may affect the serotonergic wet-dog shake syndrome in the rat partly via the cAMP signalling system but does not seem to infl uence this syndrome by changing the release of 5-HT from nerve terminals in the dorsal hippocampus. (C) 1998 Elsevier Science B.V./ECNP. All rights re served.