Basic properties of the circadian leaf movements of Oxalis regnellii, and period change due to lithium ions

The circadian leaf movement of Oxalis regnellii Mig, has been investigated. The three leaflets of a stalk were normally synchronized, and under the experimental conditions chosen they showed a period of 26.2 ± 0.1 h. Cutting off one or two leaflets led to a successive decrease of the period length (25.7 ± 0.1 and 25.1 ± 0.3 h resp.). It was possible to phase shift the leaf movements by mechanical means (advance of 1.6 ± 0.3 h).
Lithium ions, added permanently to the transpiration stream, increased the period length of the leaf movements by more than one hour (with 10 m M Li⁺). A 24 h pulse of 20 m M LiCl caused a permanent 2–3 h phase delay of the circadian rhythm. Four-h pulses, on the other hand, provoked only transient phase delays, the magnitude being dependent on the phase of application. Lithium concentrations were determined for different regions of leaves and pulvini. It was shown that leaf segments had considerably lower concentrations than pulvini. No significant difference in the lithium concentration was observed between the upper and lower part of pulvini.
In the light leaf position was strongly correlated with water uptake and the consequences for applications of substances to the circadian system via the transpiration stream is discussed. A simple model of the oscillatory system and reactions connected to it is discussed.     

Regulation of Endogenous ADP-Ribosylation by Acute and Chronic Lithium in Rat Brain

Abstract: In the present study, we investigated the effects of lithium on endogenous ADP-ribosylation in rat brain. It was found that addition of lithium in vitro inhibits endogenous ADP-ribosylation activity in extracts of frontal cortex at therapeutically relevant concentrations. Inhibition is observed at concentrations as low as 0.3 m M and is maximal at 1 m M when 50% inhibition is obtained. A similar degree of inhibition of endogenous ADP-ribosylation was observed for all substrate proteins identified, including G_sα, suggesting that lithium's effect may be achieved at the level of ADP-ribosyltransferases and not specific substrate proteins. In contrast to lithium, chloride salts of sodium and potassium do not alter endogenous ADP-ribosylation activity in frontal cortex. To assess the possible in vivo relevance of this in vitro action of lithium, we studied the effect of chronic lithium administration on levels of endogenous ADP-ribosylation in frontal cortex. It was found that chronic lithium treatment, in contrast to the inhibitory effect of the drug in vitro, produced a >35% increase in endogenous ADP-ribosylation activity. A similar degree of increase was observed for all of the substrate proteins identified. These novel findings raise the possibility that certain endogenous ADP-ribosyltransferases are among the acute targets of lithium in the brain and that adaptations in these enzymes may be part of the mechanisms underlying lithium's long-term effects on brain function.     

Lithium Chloride SCN Injection Alters the Orcadian Rhythm of Food Intake

Effect of lithium injections through chronically implanted cannulae into the bilateral suprachiasmatic nuclei (SCN) on the circadian rhythm of food intake was investigated in the rat. It was observed that the circadian rhythm was disrupted by injections of lithium at the beginning of the light as well as the dark phase of the LD cycle. In either case the percentage of the food consumed during the 12-hr light period increased while that during the dark period decreased without any significant change in the total daily intake. Disruptions in the circadian rhythm of food intake failed to show any dose-response relation. Injections of saline into the SCN or lithium into the nearby SCN area did not produce a disruption of the circadian rhythm of food intake.     

Circadian rhythms of the parameters of the mouse esophagus epithelial cell kinetics

Circadian rhythms of the mitotic activity, DNA synthesis and the parameters of the mitotic cells of the mouse esophagus epithelium were studied during the periods of maximum and minimum proliferation. The number of mitoses and DNA-synthetizing cells increases rhythmically at 1--7 a. m. from 22 p. m. to 4 a. m., respectively. When 3H-thymidine was injected to the mice at 2 a. m., tG2min was 1h; tG2+1/2 M was 2h; tS was 7.1; tG1+1/2 M was 2h; tS was 7.1; tG1+1/2 M was 15.9h. When 3H-thymidine was injected at 2 p. m., tS rose up to 8.2 and tG1+1/2 M up to 14.8h. The mitotic cycle in both series of experiments totalled 25 h. Thus, the duration of various phases of the mitotic cycle depends on the time of the day and correlates with circadian rhythms of the mitotic activity and the number of DNA-synthetizing cells. Duration of the mitotic cycle of the cells passing through it at varying time of the day is the same and approximates the period of the circadian rhythm of mitoses and DNA synthesis in esophagus epithelium.     

Differential Effects of Lithium on Muscarinic Cholinoceptor-Stimulated CMP-Phosphatidate Accumulation in Cerebellar Granule Cells, CHO-M3 Cells, and SH-SY5Y Neuroblastoma Cells

Abstract: The ability of lithium to potentiate muscarinic cholinoceptor-stimulated CMP-phosphatidate (CMP.PA) accumulation has been examined in various cells in which muscarinic cholinoceptor agonists evoke a phosphoinositide response. Cell types examined include rat cerebellar granule cells, Chinese hamster ovary cells transfected to express the human muscarinic M3 receptor (CHO-M3 cells), and SH-SY5Y neuroblastoma cells. Neither carbachol (1 m M ) nor lithium (10 m M ) caused significant increases in CMP.PA accumulation in rat cerebellar granule cells; however, when added together for 20 min a linear 17-fold increase over basal levels was observed. The increase was dependent on the concentration of carbachol and lithium present, and the effect could be reversed by addition of exogenous myo -inositol (10 m M ). Addition of carbachol alone to CHO-M3 cells caused a five-fold increase in CMP.PA accumulation. In the presence of lithium, a 70-fold increase was observed at 20 min after carbachol plus lithium addition. This latter response was concentration dependent and could be abolished by preincubation in the presence of 10 m M myo -inositol. In contrast, whereas carbachol elicited a three-fold increase in CMP.PA accumulation in SH-SY5Y neuroblastoma cells, which reached a plateau 10 min after agonist addition, the response could neither be augmented by addition of lithium nor inhibited by addition of myo -inositol. These results emphasise that the ability of lithium to affect agonist-stimulated CMP.PA accumulation is not simply a function of stimulus strength, but is also crucially dependent on the intracellular concentration of inositol.     

Glycogen synthase kinase 3beta as a likely target for the action of lithium on circadian clocks

Although lithium is one of the most commonly used drugs in the prophylaxis and treatment of bipolar disorder, the mechanisms underlying its therapeutic action are still unclear. Together with its mood-stabilizing effects, lithium is also known to influence the circadian clocks of several organisms including man. Circadian rhythms are altered in patients with bipolar disorder, and it is believed that these rhythms may play an important role in disease mechanisms. It is therefore possible that some of the therapeutic actions of lithium may be related to its effect on circadian clocks. Identifying the targets for lithium's action on circadian clocks would therefore be important both for understanding the mechanisms of its therapeutic effect and also in further understanding disease mechanisms in bipolar disorders. Using Drosophila melanogaster as a model system, we show that long-term administration of lithium results in lengthening of the free-running period (τ) of circadian locomotor activity rhythm of flies in constant darkness (DD). This effect occurs at concentrations similar to the plasma levels of lithium used in the treatment of bipolar disorder. The lithium-treated flies also show reduced activity of one of the previously reported targets of lithium action, Glycogen Synthase Kinase 3β (GSK 3β). GSK 3β has been shown to be involved in the regulation of circadian clocks as the down regulation of this protein results in an elongation of τ. The τ elongation resembles the effect seen with lithium administration in a number of organisms including man, and taken together with the earlier observations our results suggest that lithium inhibits the activity of GSK 3β to produce its effect on circadian clocks.     

Gene-Dependent Effect of Lithium on Circadian Rhythms in Mice (Mus Musculus)

Lithium has been shown to lengthen free-running circadian periods in a variety of species. Here we show that lithium carbonate differentially lengthens the free-running period of a circadian wheel running rhythm in BALB/CByJ and C57BL/10Sn inbred mouse strains. This result supports previous evidence that lithium lengthens mammalian circadian rhythms, and also demonstrates that gene differences can mediate individual differences in response to lithium treatment.     

Suppression of circadian rhythms of pineal and testicular hormones following lithium treatment in normal and reversed light-dark cycles, constant light and constant dark in rats

The aim of the current investigation was to study the effect of lithium on circadian rhythms of pineal - testicular hormones by quantitations of pineal and serum serotonin, N-acetylserotonin and melatonin, and serum testosterone at four time points (06.00, 12.00, 18.00 and 24.00) of a 24-hr period under normal photoperiod (L:D), reversed photoperiod (D:L), constant light (L:L) and constant dark phase (D:D) in rats. Circadian rhythms were observed in pineal hormones in all the combinations of photoperiodic regimens, except in constant light, and in testosterone levels in all the photoperiodic combinations. Pineal and serum N-acetylserotonin and melatonin levels were higher than serotonin at night (24.00 hr), in natural L:D cycle, in reversed L:D cycle or similar to normal L:D cycle in constant dark phase, without any change in constant light. In contrast, testosterone level was higher in light phase (12.00 hr through 18.00 hr) than in the dark phase (24.00 hr through 06.00 hr) in normal L:D cycle, in reversed L:D cycle, similar to normal L:D cycle in constant dark (D:D), and reversed to that of the normal L:D cycle in constant light (L:L). Lithium treatment (2 mEq/kg body weight daily for 15 days) suppressed the magnitude of circadian rhythms of pineal and serum serotonin, N-acetylserotonin and melatonin, and testosterone levels by decreasing their levels at four time points of a 24-hr period in natural L:D or reversed D:L cycle and in constant dark (D:D). Pineal indoleamine levels were reduced after lithium treatment even in constant light (L:L). Moreover, lithium abolished the melatonin rhythms in rats exposed to normal (L:D) and reversed L:D (D:L) cycles, and sustained the rhythms in constant dark. But testosterone rhythm was abolished after lithium treatment in normal (L:D)/reversed L:D (D:L) cycle or even in constant light/dark. The findings indicate that the circadian rhythm exists in pineal hormones in alternate light - dark cycle (L:D/D:L) and in constant dark (D:D), but was absent in constant light phase (L:L) in rats. Lithium not only suppresses the circadian rhythms of pineal hormones, but abolishes the pineal melatonin rhythm only in alternate light - dark cycles, but sustains it in constant dark. The testosterone rhythm is abolished after lithium treatment in alternate light - dark cycle and constant light/dark. It is suggested that (a) normal circadian rhythms of pineal hormones are regulated by pulse dark phase in normal rats, (b) lithium abolishes pineal hormonal rhythm only in pulse light but sustains it in constant dark phase, and (c) circadian testosterone rhythm occurs in both pulse light or pulse dark phase in normal rats, and lithium abolishes the rhythm in all the combinations of the photoperiod. The differential responses of circadian rhythms of pineal and testicular hormones to pulse light or pulse dark in normal and lithium recipients are discussed.     

Lithium Modulation of Phosphoinositide Signaling System in Rat Cortex: Selective Effect on Phorbol Ester Binding

Abstract— Recent work indicates that the therapeutic action of lithium may be mediated through perturbation of postreceptor second messenger systems. To elucidate further the postreceptor cellular sites of action(s) of lithium, the effect of chronic lithium treatment on various components of the receptor-activated phosphoinositide pathway was investigated. We found that chronic administration of lithium (0.2% LiCI, 21 days) to adult male rats did not significantly affect phosphoinositide hydrolysis in cerebral cortical slices induced by carbachol (1 m M ) or NaF (10 m M ). Nor did the same treatment alter the carbachol (1 m M ) potentiation of guanosine 5'-(γ-thio)triphosphate (30 μ M ) stimulation of phosphoinositide hydrolysis (an index of receptor/G protein coupling) in cortical membranes. Immunoblotting studies revealed no changes in the levels of Gα_q/11 immunoreactivity in the cortex after chronic lithium treatment. The levels of protein kinase C, as revealed by specific binding of [³H]phorbol dibutyrate ([³H]PDBu), were significantly reduced in the cytosolic fraction and increased in the particulate fraction of rat cortex after chronic lithium, whereas the K _D of [³H]PDBu binding remained relatively constant. A small and insignificant decrease in the density of [³H]inositol 1,4,5-trisphosphate binding was also found in the cortex. The above data suggest that chronic lithium treatment affects neither the muscarinic cholinergic-linked phosphoinositide turnover nor the putative G protein α subunit (Gα_q/11) responsible for phospholipase C activation. However, a possible translocation and activation of protein kinase C activity may be significant in the therapeutic effect of this mood-stabilizing agent.     

Mice lacking circadian clock components display different mood-related behaviors and do not respond uniformly to chronic lithium treatment

Genomic studies suggest an association of circadian clock genes with bipolar disorder (BD) and lithium response in humans. Therefore, we tested mice mutant in various clock genes before and after lithium treatment in the forced swim test (FST), a rodent behavioral test used for evaluation of depressive-like states. We find that expression of circadian clock components, including Per2, Cry1 and Rev-erbα, is affected by lithium treatment, and thus, these clock components may contribute to the beneficial effects of lithium therapy. In particular, we observed that Cry1 is important at specific times of the day to transmit lithium-mediated effects. Interestingly, the pathways involving Per2 and Cry1, which regulate the behavior in the FST and the response to lithium, are distinct as evidenced by the phosphorylation of GSK3β after lithium treatment and the modulation of dopamine levels in the striatum. Furthermore, we observed the co-existence of depressive and mania-like symptoms in Cry1 knock-out mice, which resembles the so-called mixed state seen in BD patients. Taken together our results strengthen the concept that a defective circadian timing system may impact directly or indirectly on mood-related behaviors.     

高原鼠兔肾上腺皮质功能的每日节律及急性低氧效应

机体对各种有害刺激如冷、热、毒、损伤、缺氧等均产生应激反应,表现出肾上腺皮质功能增强,皮质激素分泌增加,从而提高了机体对外界恶劣环境的适应能力与耐受能力。本文试图探讨高原上的土生动物--高原鼠兔(Ochotona curzoniae)对低氧应激反应的特点,以及高原鼠兔肾上腺皮质酮分泌的每日节律(Circadian rhythm);并与实验大鼠进行比较。     

Lithium leads to an increased FRQ protein stability and to a partial loss of temperature compensation in the Neurospora circadian clock

In many organisms, the presence of lithium leads to an increase of the circadian period length. In Neurospora crassa, it was earlier found that lithium results in a decrease of overall growth and increased circadian periods. In this article, the authors show that lithium leads to a reduction of FRQ degradation with elevated FRQ levels and to a partial loss of temperature compensation. At a concentration of 13 mM lithium, FRQ degradation is reduced by about 60% while, surprisingly, the activity of the 20S proteasome remains unaffected. Experiments and model calculations have shown that the stability of FRQ is dependent on its phosphorylation state and that increased FRQ protein stabilities lead to increased circadian periods, consistent with the observed increase of the period when lithium is present. Because in Neurospora the proteasome activity is unaffected by lithium concentrations that lead to significant FRQ stabilization, it appears that lithium acts as an inhibitor of kinases that affect phosphorylation of FRQ and other proteins. A competition between Li(+) and Mg(2+) ions for Mg(2+)-binding sites may be a mechanism to how certain kinases are inhibited by Li(+). A possible kinase in this respect is GSK-3, which in other organisms is known to be inhibited by lithium. The partial loss of temperature compensation in the presence of lithium can be understood as an increase in the overall activation energy of FRQ degradation. This increase in activation energy may be related to a reduction in FRQ phosphorylation so that more kinase activity, that is, higher temperature and longer times, is required to achieve the necessary amount of FRQ phosphorylation leading to turnover. Using a modified Goodwin oscillator as a semiquantitative model for the Neurospora clock, the effects of lithium can be described by adding lithium inhibitory terms of FRQ degradation to the model.     

Differential effect of lithium on the circadian oscillator in young and old hamsters

Lithium is one of the most commonly used drugs in the prophylaxis and treatment of bipolar disorder. It is also known to lengthen circadian period in several organisms. Previously, we reported that there was the association between lengthening circadian period by lithium and GSK-3 protein and its enzyme activity in the mouse suprachiasmatic nucleus (SCN). In this study, we show that lithium affects the circadian oscillator in young and old hamster SCN, in an age-dependent manner. We found that basal levels of phosphorylated GSK-3 (pGSK-3) protein expression in old hamsters are much lower than that in young hamsters. Furthermore, in the old hamsters, lithium did not affect the period of the locomotor activity rhythm or pGSK-3 expression, while changing period and pGSK-3 in the younger animals. These results indicate that the content of pGSK-3 in the SCN has an important role in age-dependent effects of lithium on the circadian oscillator.     

Period lengthening of human circadian rhythms by lithium carbonate, a prophylactic for depressive disorders

The effect of lithium carbonate on the circadian system of man was studied. Four out of eight volunteers living without time cues in isolated huts in the arctic showed a lengthening of the periods of the body temperature rhythm, activity rhythm, and sleep/wakefulness rhythm by c. 1 h. Four of the participants did not show a change in the periods between the placebo and lithium ingestion phases. Two subjects who did not receive lithium salt showed internal desynchronization between the temperature rhythm and the sleep/wakefulness rhythm. Extreme isolation in bunkers is not necessary to allow free running of the circadian system in man. The sleep/wakefulness rhythm, which is very easy to record, was a reliable indicator of the circadian system in the internally-synchronized state.     

The Effects of Lithium on a Neuronal in Vitro Orcadian Pacemaker

Previous studies have suggested a causal connection between abnormalities of the circadian system and affective disorders. The effectiveness of lithium or rubidium as a treatment for affective disorders and the ability of lithium or rubidium to influence circadian pacemakers has stimulated research into the mechanism of lithium's action on circadian systems. In this study we used a neuronal in vitro circadian pacemaker preparation, the eye of the mollusc Bulla, to examine the cellular effects of lithium and rubidium. Continuous extracellular LiCl application lengthens the period of the circadian rhythm of the Bulla pacemaker in a concentration-dependent manner. Rubidium was found to be more effective than lithium in period lengthening. Stable phase delays were generated by 2-h pulses of 395 mM LiCl applied extracellularly from zeitgeber time (ZT) 5-7 (mid subjective day). Concomitant continuous application of 16 mM LiCl and light (a depolarizing agent) generated period lengthening substantially greater than the arithmetic sum of the modest period lengthening of each treatment alone. Furthermore, LiCl pulses, applied together with depolarizing extracellular KC1 concentrations, yielded an increasing magnitude of phase delays with increasing KC1 concentration. These data suggest that LiCl acts intracellularly on the circadian pacemaker cells by entering through a voltage-dependent channel, most likely a sodium channel.     

Lithium does not synergize the peripheral action of cholinomimetics as seen in the central nervous system

Lithium is known to synergize the action of cholinomimetics in the CNS such that pilocarpine induces seizures in low concentration (1/13th of per se dose) in rats. The present study was undertaken to see if lithium priming also enhances the peripheral effects of acetylcholine and pilocarpine i.e. change in blood pressure in rats and contractions of the isolated guinea pig ileum. In anaesthetized rats the blood pressure was recorded from cannulated carotid artery connected through the pressure transducer to Coulbourn polygraph. The blood pressure response of pilocarpine was not different either in magnitude or in duration when administered 1, 2 and 4 h after lithium chloride (3 meq/kg) pretreatment as compared to the control. Similarly acetylcholine effect remained unchanged after lithium chloride priming. In the isolated guinea pig ileum experiments, ileum was incubated for 1 h in different concentrations of lithium chloride and effect on acetylcholine induced contractions were observed. Lithium in concentration of 2.8 x 10(-3) M had no effect on acetylcholine induced contractions while incubation with higher concentrations of 1.4 x 10(-2) M and 2.8 x 10(-2) M significant inhibition of acetylcholine contractions were observed. At this concentration, histamine induced contractions were also inhibited. The results indicate that lithium does not synergize the action of cholinomimetics in the periphery as that seen in the CNS. The inhibition of acetylcholine and histamine induced contractions in guinea pig ileum at high concentration of lithium seems to be non-specific effect.     

Expression of C-Type Natriuretic Peptide in the Bovine Pineal Gland

Abstract: The effect of lithium on inositol phospholipid resynthesis in primary cultures of cerebellar granule cells was studied. During activation of phospholipase C by the combined action of a muscarinic agonist and mild depolarization, the levels of inositol phospholipids as well as the inositol phospholipid precursor CMP-phosphatidate appeared highly sensitive to lithium with half-maximal accumulation of CMP-phosphatidate attained at 0.5 m M LiCl, a concentration close to that in the plasma of patients subjected to lithium therapy. Under the same conditions, the effect of lithium on inositol phospholipid metabolism appeared to be mediated by depletion of cytoplasmic free inositol content. This was indicated by the observation that preincubation for 48 h in high extracellular inositol concentrations could decrease or delay the depletion of inositol phospholipids and the accumulation of CMP-phosphatidate induced by 10 m M LiCl. Because even relatively high concentrations of extracellular inositol (500 µ M ) only partially prevented inositol phospholipid depletion, cerebellar granule cells appear to have a comparatively low capacity to accumulate inositol intracellularly, in comparison with other brain cells in culture. The relationship between CMP-phosphatidate accumulation and phospholipase C activity has also been investigated using a range of agonists that have been reported to act on cerebellar granule cells.     

Involvement of the role of Chk1 in lithium-induced G2/M phase cell cycle arrest in hepatocellular carcinoma cells

Lithium, a therapeutic agent for bipolar disorder, can induce G2/M arrest in various cells, but the mechanism is unclear. In this article, we demonstrated that lithium arrested hepatocellular carcinoma cell SMMC-7721 at G2/M checkpoint by inducing the phosphorylation of cdc2 (Tyr-15). This effect was p53 independent and not concerned with the inhibition of glycogen synthase kinase-3 and inositol monophosphatase, two well-documented targets of lithium. Checkpoint kinase 1 (Chk1), a critical enzyme in DNA damage-induced G2/M arrest, was at least partially responsible for the lithium action. The lithium-induced phosphorylation of cdc2 and G2/M arrest was abrogated largely by SB218078, a potent Chk1 inhibitor, as well as by Chk1 siRNA or the over-expression of kinase dead Chk1. Furthermore, lithium-induced cdc25C phosphorylation in 7721 cells and in vitro kinase assay showed that the activity of Chk1 was enhanced after lithium treatment. Interestingly, the increase of Chk1 activity by lithium may be independent of ataxia telangiectasia mutated (ATM)/ATM and Rad3-related (ATR) kinase. This is because no elevated phosphorylation on Chk1 (Ser-317 and Ser-345) was observed after lithium treatment. Moreover, caffeine, a known ATM/ATR kinase inhibitor, relieved the phosphorylation of cdc2 (Tyr-15) by hydroxyurea, but not that by lithium. Our study's results revealed the role of Chk1 in lithium-induced G2/M arrest. Given that Chk1 has been proposed to be a novel tumor suppressor, we suggest that the effect of lithium on Chk1 and cell cycle is useful in tumor prevention and therapy.     

Chronic Administration of Imipramine and Lithium Changes the Phase-Angle Relationship Between the Activity and Core Body Temperature Circadian Rhythms in Rats

Evidence suggests that there is an association between the pathophysiology of depression and a disturbance of circadian rhythms. Accordingly, attention has focused on the possible effects of antidepressants on circadian rhythms. In the present study, we examined the effects of chronic administration of two clinically effective antidepressant agents, imipramine and lithium, on several circadian rhythms in the rat. Activity, core body temperature, and drinking rhythms were assessed in constant darkness (DD) and light-dark (LD) conditions. In DD, lithium significantly lengthened the circadian period of the activity, temperature, and drinking rhythms, while imipramine had no effect. In LD, both drugs significantly delayed the phase of the activity rhythm, but did not change that of the other two rhythms. As a result, the phase-angle differences between the activity and temperature rhythms significantly increased. Neither lithium nor imipramine produced any effect on the resynchronization of these rhythms after an 8-h delay in the LD cycle. These results indicate that although both drugs produced different effects on the circadian period of individual rhythms, both caused a relative phase advance of the temperature rhythm as compared to the activity rhythm, and this effect may be related to the similarity in their antidepressant effects. (Chronobiology International, 13(4), 251-259, 1996)