Operative mortality and frequency of coexistent anomalies in interruption of the aortic arch

Operative mortality for 262 infants with interruption of the aortic arch repaired from 1982 to June 1993 has remained constant at about 35%. Major coexistent cardiac malformations, type B interruption, or staged repair are risk factors for mortality.

Visual marking: prioritizing selection for new objects by top-down attentional inhibition of old objects

The authors propose a new mechanism for prioritizing the selection of new events: visual marking. In a modified conjunction search task the authors presented one set of distractors before the remaining items, which contained the target if present. Search was as efficient as if only the second items were presented. This held when eye movements were prevented and required a gap of 400 ms between the old and new items. The effect was abolished by luminance changes at old distractor locations when the new items appeared, and it was reduced by the addition of an attention demanding load task. The authors propose that old items can be ignored by spatially parallel, top-down attentional inhibition applied to the locations of static stimuli. The authors discuss the relations between marking and other accounts of visual selection and potential neurophysiological mechanisms.

Comparative study of the determination of bupivacaine in human plasma by gas chromatography-mass spectrometry and high-performance liquid chromatography

A comparison was made between high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) as methods for determining bupivacaine in human plasma. Both methods utilized pentycaine as an internal standard, were found to be linear in the range 5-320 ng and had acceptable precision and accuracy. The precision for the HPLC method was better than that for the GC-MS method. The limits of detection of the HPLC and GC-MS methods were ca. 1.0 and 0.1 ng, respectively. Good agreement between the HPLC and GC-MS methods was obtained for the analysis of samples taken from a patient receiving bupivacaine topically. For most purposes the HPLC method would be slightly better. However, for samples containing interfering peaks GC-MS provides a higher degree of resolution from such interferants.

Chronic lithium-induced down-regulation of MARCKS in immortalized hippocampal cells: potentiation by muscarinic receptor activation

Previous studies in our laboratory have demonstrated that exposure of rats to chronic lithium results in a significant reduction in the hippocampus of levels of the protein kinase C (PKC) phosphoprotein substrate MARCKS (myristoylated alanine-rich C kinase substrate), which persists after withdrawal and is not observed following acute administration. In an immortalized hippocampal cell line (HN33), we have determined that phorbol esters rapidly down-regulate PKC activity and lead to a subsequent PKC-dependent reduction in content of MARCKS protein. We now report that chronic exposure of HN33 cells to LiCl (1-10 mM) produces a dose- and time-dependent down-regulation of MARCKS protein. The lithium-induced reduction in MARCKS is dependent on the concentration of inositol present in the medium and is reversed and prevented in the presence of elevated inositol concentrations. When HN33 cells were exposed to lithium at clinically relevant concentrations (11 mM) under limiting inositol conditions, activation of muscarinic receptor-coupled phosphoinositide signaling significantly potentiated the lithium-induced down-regulation of MARCKS protein. It has been suggested that a major action of lithium in the brain is linked to its inositol monophosphatase inhibitory activity in receptor-mediated signaling through the inositol trisphosphate/diacylglycerol pathway, resulting in a relative inositol depletion. Our data provide evidence that this initial action of lithium may translate into a PKC-dependent long-term down-regulation of MARCKS protein expression in the hippocampus.

Bioavailability of subcutaneous 5-fluorouracil: a case report

The optimal schedule for the administration of 5-fluorouracil (5-FU) in the management of advanced colorectal cancer remains to be determined. It has been suggested that this drug may be given by the subcutaneous route and that following a short infusion the bioavailability is similar to that observed after intravenous administration. We report the results we obtained in a patient treated with an intravenous bolus of 5-FU followed by a 22-h subcutaneous infusion. In this patient the bioavailability of 5-FU given by subcutaneous infusion was 0.94. The steady-state plasma levels of 5-FU reached during subcutaneous infusion were comparable with those achieved during intravenous infusion. Following four cycles of subcutaneous therapy, painless blistering was noted at the infusion sites, which healed following the cessation of subcutaneous therapy. Further studies are required to evaluate this route of therapy as an alternative to protracted intravenous therapy. The main dose-limiting side effect appears to the local skin toxicity.

Synthesis and characterisation of acyl glycines. Their measurement in single blood spots by gas chromatography-mass spectrometry to diagnose inborn errors of metabolism

Acyl glycines are normally minor metabolites of fatty acids; however, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. Therefore measurement of the metabolites in body fluids can be used to diagnose these metabolic disorders. The chemical synthesis of a range of acyl glycines is described, together with that of their 13C2-isotopomers for use as internal standards. An analytical method for the measurement of hexanoyl, octanoyl, 3-phenylpropionyl and suberyl glycines in urine, employing gas chromatography-mass spectrometry with negative-ion chemical ionisation was adapted to measure a larger range of acyl glycines in a single blood spot on a standard Guthrie card. Diagnoses of a case of medium-chain acyl-CoA dehydrogenase deficiency and a case of isovaleric acidaemia were confirmed using a single blood spot from each patient.

Myristoylated alanine-rich C kinase substrate (MARCKS): a molecular target for the therapeutic action of mood stabilizers in the brain?

BACKGROUND

Lithium remains a first-line treatment for the acute and prophylactic management of bipolar illness. Previous studies in our laboratory have demonstrated that chronic, but not acute, exposure to therapeutic concentrations of lithium significantly reduces the expression of the protein kinase C (PKC) substrate MARCKS (myristoylated alanine-rich C kinase substrate) in the rat hippocampus and an immortalized hippocampal cell line (HN33). The anticonvulsant drugs valproate and carbamazepine are emerging as efficacious alternative and adjunctive treatments for bipolar disorder. In the present study, we sought to determine the effects of valproate and carbamazepine on MARCKS protein levels by using our hippocampal cell model.

METHOD

HN33 immortalized hippocampal cells were exposed acutely or chronically to sodium valproate 1 mM, carbamazepine 100 microM, lithium chloride 5 mM, or lithium chloride 5 mM + sodium valproate 1 mM. Additionally, cells were exposed to lithium chloride 5 mM in the absence or presence of inositol 5 microM, or sodium valproate 1 mM in the absence or presence of inositol 40 microM. After drug exposure, cells were collected, separated into soluble and membrane fractions, and MARCKS protein assayed by Western blot analysis using polyclonal rabbit antibody. Immunoreactive bands were quantitated by densitometric analysis.

RESULTS

We report that chronic exposure of HN33 cells to either lithium or valproate produced a time-dependent down-regulation of MARCKS protein. Maximal reduction in MARCKS levels were observed after 3 days of exposure to valproate and after 7 days of exposure to lithium. The reduction of MARCKS produced by lithium and valproate alone were additive when the two drugs were combined. The reduction in MARCKS produced by lithium was reversed by the addition of inositol to the media, whereas the reduction produced by valproate was unaffected by the addition of inositol. Carbamazepine failed to affect MARCKS protein levels at each dose and time tested.

CONCLUSION

These data provide evidence that, like lithium, chronic exposure to valproate produces a significant time-dependent down-regulation of the PKC substrate MARCKS, whereas carbamazepine is without effect. The MARCKS reduction produced by valproate appears to occur independently of inositol concentrations yet is additive with the reduction produced by lithium, which is inositol-reversible. Valproate- and lithium-induced regulation of MARCKS expression appears to be mediated by different mechanisms that may utilize PKC, and may be associated with the clinical profile of these mood stabilizers. Regulation of MARCKS expression may be associated with the prophylactic efficacy of lithium in the long-term stabilization of the recurrent affective episodes in bipolar disorder, and valproate may share this property.

Metabolism by Schistosoma mansoni of a new schistosomicide: 2-[(1-methylpropyl)amino]-1-octanethiosulphuric acid

In order to investigate the mode of action of a new class of schistosomicides, the N-alkylaminoalkanethiosulphuric acids, the [outer 25S] 2-[(1-methylpropyl)amino]-1-octanethiosulphuric acids was synthesized. Labelling studies of adult Schistosoma mansoni were performed in infected mice and in in vitro incubations. After a single oral dose of the drug to infected mice, 5 metabolites were detected by thin-layer chromatogrpahy in organic extracts of male and female adult schistosomes. In vitro studies showed that the same compounds were present in organic extracts obtained from adult male and female worms. One of these metabolites was identified by mass spectroscopy as being the dimeric disulphide derivative of the parent labelled thiosulphuric acid.

Attention capture by contour onsets and offsets: no special role for onsets

In five experiments, we investigated the power of targets defined by the onset or offset of one of an object's parts (contour onsets and offsets) either to guide or to capture visual attention. In Experiment 1, search for a single contour onset target was compared with search for a single contour offset target against a static background of distractors; no difference was found between the efficiency with which each could be detected. In Experiment 2, onsets and offsets were compared for automatic attention capture, when both occurred simultaneously. Unlike in previous studies, the effects of overall luminance change, new-object creation, and number of onset and offset items were controlled. It was found that contour onset and offset items captured attention equally well. However, display size effects on both target types were also apparent. Such effects may have been due to competition for selection between multiple onset and offset stimuli. In Experiments 3 and 4, single onset and offset stimuli were presented simultaneously and pitted directly against one another among a background of static distractors. In Experiment 3, we examined "guided search," for a target that was formed either from an onset or from an offset among static items. In Experiment 4, the onsets and offsets were uncorrelated with the target location. Similar results occurred in both experiments: target onsets and offsets were detected more efficiently than static stimuli which needed serial search; there remained effects of display size on performance; but there was still no advantage for onsets. In Experiment 5, we examined automatic attention capture by single onset and offset stimuli presented individually among static distractors. Again, there was no advantage for onset over offset targets and a display size effect was also present. These results suggest that, both in isolation and in competition, onsets that do not form new objects neither guide nor gain automatic attention more efficiently than offsets. In addition, in contrast to previous studies in which onsets formed new objects, contour onsets and offsets did not reliably capture attention automatically.

Analysis of unconjugated morphine, codeine, normorphine and morphine as glucuronides in small volumes of plasma from children

A sensitive method for the analysis of unconjugated morphine, codeine, normorphine and total morphine after hydrolysis of glucuronide conjugates is described. The method was applicable to 50-microliters volumes of plasma. The analytes were converted to heptafluorobutyryl (HFB) derivatives before analysis by gas chromatography-negative ion chemical ionization mass spectrometry. Morphine and codeine were quantified against their [2H3]-isotopomers. Linearity, precision and accuracy were quite acceptable (in the 10(-10)-10(-9) g range), and the absolute limits of detection were < 1 pg.

Phorbol ester- and retinoic acid-induced regulation of the protein kinase C substrate MARCKS in immortalized hippocampal cells

The expression of MARCKS, a major protein kinase C (PKC) substrate, was examined in the immortalized hippocampal cell line HN33, following differentiation using phorbol esters or retinoic acid. In cells exposed to phorbol esters, MARCKS protein levels were reduced through an apparent PKC-dependent mechanism. Exposure to 1 microM phorbol 12-myristate 13-acetate (PMA) for 10 min resulted in a rapid loss of PKC activity in the soluble fraction with a concurrent increase in membrane-associated PKC activity. PKC activity was reduced to < 20% of control values in both soluble and membrane fractions following 1 h of PMA exposure. Significant reductions in MARCKS protein levels were initially observed in membrane and soluble fractions following PMA exposure for 4 and 8 h, respectively. The reduction in MARCKS protein levels was maximal following 24 h of PMA exposure. MARCKS protein expression was also down-regulated in a dose-dependent manner on exposure of HN33 cells to retinoic acid. In cells exposed to 10 microM retinoic acid, the MARCKS protein level was reduced in the membrane fraction within 4 h. Reduction of MARCKS protein levels was maximal (> 90%) by 12 h with no evidence for any alteration in PKC activity. Reduced levels of MARCKS protein were also observed in the soluble fraction of retinoic acid-exposed cells, but to a significantly lesser extent. Addition of the PKC inhibitor GF109203X blocked the down-regulation of MARCKS protein in PMA-treated cultures but not in retinoic acid-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Object recognition under sequential viewing conditions: evidence for viewpoint-specific recognition procedures

In many computational approaches to vision it has been emphasised that object recognition involves the encoding of view-independent descriptions prior to matching to a stored object model, thus enabling objects to be identified across different retinal projections. In contrast, neurophysiological studies suggest that image descriptions are matched to less abstract, view-specific representations, resulting in more efficient access to stored object knowledge for objects presented from a view similar to a stored viewpoint. Evidence favouring a primary role for view-specific object descriptions in object recognition is reported. In a series of experiments employing line drawings of familiar objects, the effects of depth rotation upon the efficiency of object recognition were investigated. Subjects were required to identify an object from a sequence of very briefly presented pictures. The results suggested that object recognition is based upon the matching of image descriptions to view-specific stored representations, and that priming effects under sequential viewing conditions are strongly influenced by the visual similarity of different views of objects.

Carrier-free 131I-meta-iodobenzylguanidine: comparison of production from meta-diazobenzylguanidine and from meta-trimethylsilylbenzylguanidine

Meta-iodobenzylguanidine (MIBG) is a drug which is selectively accumulated by the uptake-1 process in adrenergic tissues. When labelled with 131I, it may be used for the targetted radiotherapy of tumours such as phaeochromocytoma and neuroblastoma. This paper describes the preparation of carrier-free 131I-MIBG by radioiodination of meta-diazobenzylguanidine, and compares this process with one involving iododesilylation of meta-trimethylsilylbenzylguanidine. Both processes result in the formation of carrier-free 131I-MIBG whose specific activity at greater than 3 x 10(16) Bq mol-1 is at least 100 times higher than that of commercially available 131I-MIBG for therapeutic use. The therapeutic use of 131I-MIBG with a higher than usual specific activity is predicted to result in a greater target-to-nontarget ratio, and therefore enhanced efficacy because of an increased therapeutic index. As the radiochemical yield of the process involving the metadiazobenzylguanidine intermediate is only 13%, compared with 98% for the iododesilylation reaction, the latter is the preferred synthetic route.

Lithium and the brain: a psychopharmacological strategy to a molecular basis for manic depressive illness

Lithium, an effective treatment for mania and the prevention of recurrent episodes of both mania and depression in patients with manic depressive illness, exerts multiple biochemical effects. However, any clinically relevant site of action of lithium must occur at therapeutic concentrations attained in the brain of patients and must account for the lag period accompanying onset of action as well as effects persisting beyond discontinuation of treatment. This monovalent cation acts as a potent uncompetitive inhibitor in the receptor-coupled breakdown of inositol phospholipids, resulting in a relative depletion of inositol and an alteration in the generation of diacylglycerol, an endogenous activator of protein kinase C. In our laboratory, we are examining the action of chronically administered lithium on posttranslational modification of specific phosphoproteins involved in regulating signal transduction in the brain. We have found that chronic, but not acute, administration of lithium in rats markedly reduces a major phosphoprotein substrate of protein kinase C in the hippocampus, an effect that persists beyond the cessation of lithium treatment. This protein, myristoylated alanine-rich C kinase substrate ("MARCKS"), is implicated in synaptic neurotransmission, calcium regulation, and cytoskeletal restructuring. These findings have relevance for the long-term action of lithium in stabilizing an underlying dysregulation in the brain and may move us closer to formulating a molecular basis of manic depressive illness.

Lithium and the brain: a psychopharmacological strategy to a molecular basis for manic depressive illness

Lithium, an effective treatment for mania and the prevention of recurrent episodes of both mania and depression in patients with manic depressive illness, exerts multiple biochemical effects. However, any clinically relevant site of action of lithium must occur at therapeutic concentrations attained in the brain of patients and must account for the lag period accompanying onset of action as well as effects persisting beyond discontinuation of treatment. This monovalent cation acts as a potent uncompetitive inhibitor in the receptor-coupled breakdown of inositol phospholipids, resulting in a relative depletion of inositol and an alteration in the generation of diacylglycerol, an endogenous activator of protein kinase C. In our laboratory, we are examining the action of chronically administered lithium on posttranslational modification of specific phosphoproteins involved in regulating signal transduction in the brain. We have found that chronic, but not acute, administration of lithium in rats markedly reduces a major phosphoprotein substrate of protein kinase C in the hippocampus, an effect that persists beyond the cessation of lithium treatment. This protein, myristoylated alanine-rich C kinase substrate ("MARCKS"), is implicated in synaptic neurotransmission, calcium regulation, and cytoskeletal restructuring. These findings have relevance for the long-term action of lithium in stabilizing an underlying dysregulation in the brain and may move us closer to formulating a molecular basis of manic depressive illness.

The metabolism of fluorometholone by bovine cornea

Isolated bovine cornea was found to reduce the 20 ketone group in fluorometholone (FML) to produce a mixture of 20 alpha- and 20 beta-dihydrofluorometholone (DHFML). Incubation of FML with bovine cornea at pH 7.4 in phosphate buffer produced an increase in the amount of reduction products up to 8 h; after this time the rate of reduction decreased. The reduced products were quantified by GC-MS against [2H3] 20 alpha-DHFML. Variable amounts of 20 beta-DHFML were detected in six samples of human aqueous humour following topical application of 50 micrograms of FML to the eye. The rapid metabolism of the side chain of FML may account for the unexpected low concentrations of FML which are found in human aqueous humour following its application to the surface of the eye.

Analysis of biogenic amines in plasma of hypertensive patients and a control group

Procedures were developed for the determination of 17 circulating amines using gas chromatography-negative ion chemical ionisation mass spectrometry. The amines were quantified against their appropriate deuterated isotopomers. The mean concentrations and ranges of catecholamines and trace amines were high compared with previous studies. In comparison with nonhypertensives, plasma from hypertensives had higher concentrations of the following amines: noradrenaline (t = 4.0%); normetanephrine (t = 6.1%) and metanephrine (t = 1.9%). There were no significant differences between 5HT levels in plasma from hypertensives and controls. The following trace amines could be detected in variable amounts in plasma: p-tyramine, m-tyramine, p-octopamine, m-octopamine, p-synephrine, m-synephrine, and salsolinol. The trace amines melatonin, N-acetyl 5HT, tryptamine, 6-hydroxymelatonin and 5-methoxytryptamine could not be detected in plasma with limits of detection lying in the range 20-100 pg ml-1.

The determination of hydroxydopamines and other trace amines in the urine of parkinsonian patients and normal controls

5- and 6-Hydroxydopamine, which we had earlier identified as naturally occurring amines in human urine, were quantified in Parkinson's patients treated with L-DOPA, Parkinson's patients whose treatment did not include L-DOPA and in age matched controls. Analysis was carried out by GC-MS of the ditrifluoromethylbenzoyl-trimethylsilyl (DTFMB-TMS) derivatives of the compounds. The concentrations of 5- and 6-hydroxydopamine in the urine of DOPA treated Parkinson's patients were significantly higher than the concentrations from patients not treated and from normal controls. Urinary dopamine levels were greatly elevated in DOPA treated Parkinson's patients while p-tyramine levels were suppressed. No marked differences were seen between the three groups in terms of the urinary concentrations of any of the other amines measured.

The determination of biogenic amines in four strains of the fruit fly Drosophila melanogaster

A range of biogenic amines were measured in the heads from four strains of Drosophila melanogaster. Quantitation was carried out using gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) with stable isotope dilution. The principal amines detected in the heads were dopamine, noradrenaline and 5 HT with small amounts of p- and m-tyramine; p-octopamine could not be detected in samples of 25 heads with a limit of detection of 10 pg per sample. In addition to conventional neurotransmitters or putative neurotransmitters the amines 5- and 6-hydroxydopamine were detected in the heads in substantial amounts.

Identification and quantification of gamma-glutamyl conjugates of biogenic amines in the nervous system of the snail, Helix aspersa, by gas chromatography-negative-ion chemical ionisation mass spectrometry

The gamma-glutamyl conjugates of p-octopamine and dopamine were identified unambiguously for the first time and quantified in a single cerebral ganglion or pleural plus pedal ganglia of the snail, Helix aspersa, by gas chromatography-negative-ion chemical ionisation mass spectrometry. A new method was used for synthesis of gamma-glutamylamine standards. The concentration of gamma-glutamyltyramine was found to be low in the tissues, therefore it was used as an internal standard. The gamma-glutamylamines were extracted with water and derivatised with pentafluoropropionic anhydride and trifluoroethanol. Under negative-ion chemical ionisation conditions, the trifluoroethyl and pentafluoropropionyl derivatives produced significant ions which were sufficiently abundant to be suitable for selective ion monitoring. The method had a limit of detection of ca. 80 pg of gamma-glutamyl conjugate per tissue and calibration curves were linear over the range examined.

The determination of 5-hydroxytryptamine, related indolealkylamines and 5-hydroxyindoleacetic acid in the bovine eye by gas chromatography-negative ion chemical ionization mass spectrometry

Methods were developed for the analysis of 5-hydroxytryptamine, related indolealkylamines (tryptamine, melatonin, 5-methoxytryptamine, N-acetyl-5-hydroxytryptamine and 6-hydroxymelatonin) and 5-hydroxyindole-3-acetic acid (5HIAA) in bovine retina, aqueous and vitreous humours. 5-Hydroxytryptamine and related indolealkylamines were extracted and derivatized to form their corresponding pentafluoropropionyl spirocyclic derivatives. 5HIAA was extracted and derivatized to the corresponding pentafluoropropionamide-trifluoroethyl derivative. Identification and quantitation by gas chromatography-negative ion chemical ionization mass spectrometry was made with reference to deuteriated internal standards. 5-Hydroxytryptamine was present in all (n = 34) retinal samples analysed (20.53 +/- 1.64 ng) while N-acetyl-5-hydroxytryptamine was detected in half of the samples of retina (0.06 +/- 0.02 ng). Melatonin (0.15 +/- 0.06 ng) and tryptamine (0.78 +/- 0.34 ng) were detected in only a small number of retinas. 5-Methoxytryptamine was not present in retina. 5-Hydroxytryptamine was also present in aqueous (0.76 +/- 0.17 ng ml-1 and vitreous (0.35 +/- 0.05 ng ml-1' humours from bovine eye. Tryptamine, melatonin, 5-methoxytryptamine and N-acetyl-5-hydroxytryptamine were not detected in bovine aqueous and vitreous humours. 5HIAA was found in both bovine aqueous (2.03 +/- 0.38 ng ml-1) and vitreous (0.65 +/- 0.06 ng ml-1) humours, but its consistent determination in retina was obviated by interference from spurious peaks.

Measurement of ascorbic acid in human aqueous humour and plasma and bovine aqueous humour by high-performance liquid chromatography with electrochemical detection

High-performance liquid chromatography (HPLC) on ODS silica with cetyltrimethylammonium bromide as an ion-pairing reagent and electrochemical detection (ECD) was used to determine ascorbic acid in bovine and human aqueous humour and human plasma. Hydroquinone was used as the internal standard. A calibration curve plotted with ascorbic acid concentrations in the range 0.5-5 micrograms ml-1 for peak height versus internal standard peak height had a correlation coefficient of 0.998. The RSD (precision) between analyses of the same diluted sample was 1.5% and the RSD (reproducibility) between analyses of separate aliquots of the same sample of aqueous humour was 1.6%.

Assay of certain oral contraceptive formulations by gas chromatography-mass spectrometry-selected ion monitoring

The combined technique of gas chromatography--mass spectrometry--selected ion monitoring (GC-MS-SIM) has been employed for the nanogram level determination of ethinyloestradiol, mestranol, norgestrel and norethisterone in various oral contraceptive formulations. Steroids were assayed as their DMES-or methoxime DMES ether derivatives in the presence of ethisterone as the internal standard. The method is accurate, specific and suitable for single tablet assay.

Chronic lithium administration alters a prominent PKC substrate in rat hippocampus

The therapeutic effect of lithium in the treatment of bipolar disorder exhibits a significant delay in the onset of action and a persistence of efficacy beyond abrupt discontinuation of treatment. Lithium is known to alter receptor-coupled phosphoinositide second messenger pathway in brain, resulting in indirect changes in an endogenous activator of protein kinase C (PKC). Such evidence has suggested that PKC may be involved in the mechanism of action of lithium in the brain. PKC represents a site wherein long-term regulatory changes in cell function occur through the phosphorylation of specific phosphoproteins involved in processes including neurotransmitter release and receptor activation. In studies of rats exposed to lithium, however, we have found no significant effects of chronic administration on the relative activity, subcellular distribution, or activation of PKC in hippocampus. We did find a major reduction in the in vitro PKC mediated phosphorylation of two major substrates, 83 kDa and 45 kDa, in hippocampus of rats exposed to chronic lithium and maintaining clinically relevant therapeutic levels in brain. Using immunoblot analysis we have identified a known myristoylated alanine-rich C kinase substrate (MARCKS) at 83 kDa. In vivo levels of MARCKS in hippocampus were found to be significantly reduced after chronic lithium exposure. These findings persist in animals withdrawn from lithium, but are not apparent following acute treatment.(ABSTRACT TRUNCATED AT 250 WORDS)