The influence of lithium on water binding ability, consistency and macromolecules in the rat brain

Hyaluronan and its function as an unspecific regulator of cell-bound receptors

In a former study on primary mesangial cells a regulatory function of hyaluronan (HA) was shown. HA is the backbone of a cell-bound jelly-barrier. The thickness of that cell-bound jelly-barrier regulates the access of ligands to their cellular receptors in an unspecific way. The thickness of that barrier is reduced by degradation of HA. The hypothesis was that this regulatory mechanism is not restricted to mesangial cells, but applies for other cell types as well. A selective and topic oriented review of the literature was performed to collect references, which support the impression, that this unspecific mechanism of receptor-regulation by HA is not restricted to primary mesangial cells. On the basis of the data from the review of the literature it was concluded that the regulatory mechanism of HA also applies for other than mesangial cells. On the basis of the said mechanism it was concluded that a tissue-specific regulation of HA on the cell surface might be relevant in therapy, especially in chronic diseases.

Contrasting effects of haloperidol and lithium on rodent brain structure: a magnetic resonance imaging study with postmortem confirmation

BACKGROUND

Magnetic resonance imaging (MRI) studies suggest that antipsychotic -treated patients with schizophrenia show a decrease in gray-matter volumes, whereas lithium-treated patients with bipolar disorder show marginal increases in gray-matter volumes. Although these clinical data are confounded by illness, chronicity, and other medications, they do suggest that typical antipsychotic drugs and lithium have contrasting effects on brain volume.

METHODS

Rodent models offer a tractable system to test this hypothesis, and we therefore examined the effect of chronic treatment (8 weeks) and subsequent withdrawal (8 weeks) with clinically relevant dosing of an antipsychotic (haloperidol, HAL) or lithium (Li) on brain volume using longitudinal in vivo structural MRI and confirmed the findings postmortem using unbiased stereology.

RESULTS

Chronic HAL treatment induced decreases in whole brain volume (-4%) and cortical gray matter (-6%), accompanied by hypertrophy of the corpus striatum (+14%). In contrast, chronic Li treatment induced increases in whole-brain volume (+5%) and cortical gray matter (+3%) without a significant effect on striatal volume. Following 8 weeks of drug withdrawal, HAL-induced changes in brain volumes normalized, whereas Li-treated animals retained significantly greater total brain volumes, as confirmed postmortem. However, the distribution of these contrasting changes was topographically distinct: with the haloperidol decreases more prominent rostral, the lithium increases were more prominent caudal.

CONCLUSIONS

The implications of these findings for the clinic, potential mitigation strategies, and further drug development are discussed.

Lithium and inositol: effects on brain water homeostasis in the rat

RATIONALE

Since its earliest use in psychiatry, lithium has been known to alter body water homeostasis. Although lithium is also known to decrease the concentration of inositol, an important brain osmolyte, little is known of the effects of lithium on brain water homeostasis.

OBJECTIVE

To determine whether lithium alters brain water homeostasis, and, if so, whether the mechanism involves changes in inositol concentration.

MATERIALS AND METHODS

Rats were fed regular food or regular food plus lithium chloride for either 11 days or 5 weeks. Brains were dissected and assayed for tissue water by the wet-dry method and for inositol by gas chromatography-mass spectrometry.

RESULTS

We found a statistically significant (p=0.05, corrected) 3.1% mean elevation in frontal cortex tissue water in 5-week lithium-fed rats (86.7+/-3.9%), compared to control rats (83.6+/-2.6%). Inositol concentration correlated inversely with percent tissue water (r=-0.50, p=0.003, corrected) in pooled samples of 5-week lithium-fed rats, and was significantly lower in frontal cortex and hippocampus of 5-week lithium-fed rats, compared to controls. Rats fed lithium for 11 days did not differ significantly from controls on either variable.

CONCLUSIONS

This is the first report of a lithium-induced increase in brain tissue water. Although the mechanism is unclear, it does not appear to result from changes in brain inositol concentration or blood sodium concentration. This finding may have implications for the therapeutic or toxic effects of lithium on brain, because increased tissue water can augment cell excitability.

No change in rat cerebral cortex calmodulin content following chronic treatment with lithium, reserpine, imipramine, and lithium combined with reserpine or imipramine

Rats were treated 2-3 weeks with lithium, reserpine, imipramine, and combinations of lithium with reserpine or imipramine. Lithium was given in the diet, while the other drugs were dissolved in 0.9% saline and given intraperitoneally twice daily. The control and lithium groups received only vehicle injections. Twenty-four hours after the last injection the rats were decapitated and the cerebral cortex dissected. The tissue was sliced and the noradrenaline-stimulated cyclic AMP accumulation determined or the tissue was homogenized and centrifuged at 10,000 X g for 30 min. and the calmodulin content determined in the pellet and the supernatant. Reserpine treatment was found to cause an 50% increase in the noradrenaline-stimulated cyclic AMP accumulation, while treatment with imipramine and the combination lithium-imipramine decreased the noradrenaline-stimulated cyclic AMP accumulation by 40%. The tissue content of calmodulin was, however, found unaltered by all treatments.

The effect of long-term lithium treatment on the incorporation and distribution of 32P-orthosphosphate into the phospholipids from rat synaptosomes

Rats were treated with lithium added to their diet for five weeks (40 mmol LiCl/kg diet). Mean plasma concentration was 0.45 mmol Li+/plasma. The investigation was divided into two sections. I) In an in vivo experiment in which the rats were injected with 32P-orthosphosphate for 20 hours, and with carbamoylcholine for 20 min. prior to their death, the distribution of 32P in the synaptosomal phospholipids, phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and phosphatidylcholine (PC), was investigated. II) An in vitro experiment which was carried out in order to establish the effect of carbamoylcholine on the incorporation of 32P into total phospholipids from extracted synaptosomes. In I) the incorporation of 32P-orthosphosphate into PI from carbamoylcholine-stimulated rats was significantly lower than from unstimulated rats, whereas there was no difference between the incorporation of 32P into PI from synaptosomes from control animals and lithium-treated animals. In II) the incorporation of 32P-orthosphosphate was significantly lower in unstimulated synaptosomes from lithium-treated rats than from control rats, while the increase in the 32P-incorporation after stimulation followed the same pattern with regard to synaptosomes from control rats and lithium-treated rats. The results support the idea of lithium exerting an effect on basal synaptosomal activity but not on stimulated synaptosomal activity.

Lithium and chlorimipramine differentially alter the stability properties of tryptophan hydroxylase as seen in allosteric and scattering kinetics

Compared to control, both lithium and chlorimipramine (CMI) slow the frequency of variation in tryptophan hydroxylase (TPOH) velocity functions measured across increasing (nearly physiological) cofactor concentrations or across continuous (long residence) time. The common effect appears to be generated by different statistical mechanisms in view of the diverse patterns observed when, for multiple 60-point experiments for each condition, mean frequencies were plotted against mean amplitudes of variation: lithium constricted the frequencies over a range of amplitudes; CMI fixed amplitude across the range of frequencies. Initial rate, short residence time experiments suggest that at the micromolecular level, before the emergence of time-dependent macro-kinetic organization as seen in the long residence time assays, lithium may uncouple the elementary constituents of the system, allowing subsequent phase gathering and emergent stability around a statistically dominant frequency, whereas CMI may augment coupling, leading to unstable complexity in the population dynamics. The relationship between these effects and allosteric kinetic functions is discussed.

Scattering kinetics in a complex tryptophan hydroxylase preparation from rat brainstem raphe nuclei: statistical evidence that the lithium-induced sigmoid velocity function reflects two states of available catalytic potential

Multiple measures on statistical patterns from a kinetic scattering paradigm for the activities of rat brainstem medial and dorsal raphé nuclear tryptophan hydroxylase preparations are consistent with the previous hypothesis (J. Neural Transmission 45: 1-15, 1979) that the lithium ion induces a state of kinetic bistability in the system. In this context, the lithium-induced sigmoid tetrahydrobiopterin-reaction velocity function is interpreted as a jump between two stable states of differing catalytic potential with a less kinetically accessible domain between them. These dynamics are qualitatively portrayed in three dimensions by Thom's classical cusp catastrophe.

The effect of chronic lithium treatment on the sialic acid content in rat brain synaptosomes

Rats were fed a lithium-containing diet for five weeks (40 mmol LiCl/kg fodder). Plasma lithium concentration was 0.44 mmol Li+/l plasma. The synaptosomes were isolated an incubated with 3H-glucosamine for 60 min. The glycopeptides and the gangliosides were extracted and the sialic acid content and the 3H-sialic acid content were measured. The lithium treatment produced an increase in the synaptosomal glycopeptide content. The sialic acid content was simultaneously increased in glycopeptides as well as gangliosides. The specific activity of sialic acid was reduced to 75% of the control value in the sialoglycopeptide fraction.

The effect of lithium on the incorporation of 3H-glucosamine into glycopeptides and the transformation of 3H-glucosamine into sialic acid in rat brain

Rats were fed a lithium-containing diet (40 mmol LiCl/kg of diet) for five weeks. The plasma-lithium concentration was 0.48 mmol Li+/l of plasma. 3H-glucosamine (400 nCi/kg body weight was injected intraperitoneally, and 24 hrs later the brain was divided anatomically into hemisphere, cerebellum, pons and thalamus. The brain parts were defatted and the sialic acid-containing glycopeptides were separated by column chromatography before determination of 3H-glucosamine, 3H-sialic acid and total sialic acid. Neither the total amount nor the specific activity of sialic acid were influenced by the lithium treatment. Also the 3H-content of the sialic acid-free glycopeptides remained unchanged.

The effect of lithium on the incorporation of 32P-orthophosphate into synaptosomal phospholipids from rat brain

Rats were treated with lithium added to the diet for five weeks (40 mmol LiCl/kg diet). The mean plasma lithium concentration was 0.48 mmol/l plasma, and the blood was drawn at 8 a.m. The brains were removed and synaptosomes were prepared according to the method of Gray & Whittaker (1962) and Bradford (1972). The synaptosomes were incubated for 120 min. with 32P-orthophosphate, either in a lithium-containing medium or in a lithium-free medium. The 32P-incorporation was lower in the synaptosomes from lithium-treated rats than the 32P-incorporation in synaptosomes from control rats regardless of the medium chosen. The results indicate that lithium treatment in vivo decreases the 32P-incorporation into synaptosomal phospholipids and that the effect remains after the removal of the lithium ion.