title: Effect of chronic lithium treatment on rat pineal rhythms: N-acetyltransferase, N-acetylserotonin and melatonin.
abstract: Chronic lithium treatment in rats suppressed the peak activity of pineal N-acetyltransferase as well as the maximal concentrations of pineal N-acetylserotonin and melatonin which occur during the dark phase of the light/dark cycle. These changes were not related to changes in the precursor indoles tryptophan, 5-hydroxytryptophan and serotonin, which were unaltered by lithium treatment. The change in N-acetyltransferase activity appears in part to be due to a decreased Vmax of the enzyme, as assessed using tryptamine as the substrate. Lithium also suppressed pineal activity during the light phase of the diurnal lighting cycle as indicated by a markedly reduced cyclic AMP response to L-isoproterenol. In addition, lithium treatment elicited a 1- to 3-hr delay in peak pineal N-acetyltransferase activity. These effects may result from a lithium-induced desensitization of pineal beta adrenergic receptors, from a direct effect of the ion on the suprachiasmatic nucleus and/or from an action on a site distal to this hypothalamus nucleus.
mesh_terms: D006916:5-Hydroxytryptophan / Q000378:metabolism; D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002940:Circadian Rhythm / Q000187:drug effects; D000242:Cyclic AMP / Q000096:biosynthesis; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007545:Isoproterenol / Q000008:administration & dosage; D008094:Lithium / Q000008:administration & dosage*; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D010870:Pineal Gland / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000031:analogs & derivatives* / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D008094:Lithium; D006916:5-Hydroxytryptophan; D000242:Cyclic AMP; D000123:Acetyltransferases; D008550:Melatonin; D007545:Isoproterenol; C006389:N-acetylserotonin