Omega-3 fatty acids prevent the ketamine-induced increase in acetylcholinesterase activity in an animal model of schizophrenia.

AIMS: Schizophrenia is a debilitating neurodevelopmental disorder that is associated with dysfunction in the cholinergic system. Early prevention is a target of treatment to improve long-term outcomes. Therefore, we evaluated the preventive effects of omega-3 fatty acids on AChE activity in the prefrontal cortex, hippocampus and striatum in an animal model of schizophrenia. MAIN METHODS: Young Wistar rats (30 days old) were initially treated with omega-3 fatty acids or vehicle alone. Animals received ketamine to induce an animal model of schizophrenia or saline plus omega-3 fatty acids or vehicle alone for 7 consecutive days beginning on day 15. A total of 22 days elapsed between the treatment and intervention. Animals were sacrificed, and brain structures were dissected to evaluate AChE activity and gene expression. KEY FINDINGS: Our results demonstrate that ketamine increased AChE activity in these three structures, and omega-3 fatty acids plus ketamine showed lower values for the studied parameters, which indicate a partial preventive mechanism of omega-3 fatty acid supplementation. We observed no effect on AChE expression. Together, these results indicate that omega-3 fatty acid supplementation effectively reduced AChE activity in an animal model of schizophrenia in all studied structures. In conclusion, the present study provides evidence that ketamine and omega-3 fatty acids affect the cholinergic system, and this effect may be associated with the physiopathology of schizophrenia. Further studies are required to investigate the mechanisms that are associated with this effect.

Dysregulation of dopamine signaling in the dorsal striatum inhibits feeding.

Dopamine signaling is an important component of many goal-directed behaviors, such as feeding. Acute disruption of dopamine signaling using pharmacological agents tends to inhibit normal feeding behaviors in rodents. Likewise, genetically engineered dopamine-deficient (DD) mice are unable to initiate sufficient feeding and will starve by approximately 3 weeks of age if untreated. Adequate feeding by DD mice can be achieved by daily administration of L-3,4-dihydroxyphenylalanine (L-dopa), a precursor of dopamine, which can be taken up by dopaminergic neurons, converted to dopamine, and released in a regulated manner. In contrast, adequate feeding cannot be restored with apomorphine (APO), a mixed agonist that activates D1 and D2 receptors. Viral restoration of dopamine production in neurons that project to the dorsal striatum also restores feeding in DD mice. Administration of amphetamine (AMPH) or nomifensine (NOM), drugs which increase synaptic dopamine concentration, inhibits food intake in virally rescued DD mice (vrDD) as in control animals. These results indicate that the dysregulation of dopamine signaling in the dorsal striatum is sufficient to induce hypophagia and suggest that regulated release of dopamine in that brain region is essential for normal feeding and, probably, many other goal-directed behaviors.

S-Allylcysteine, a garlic-derived antioxidant, ameliorates quinolinic acid-induced neurotoxicity and oxidative damage in rats.

Excitotoxicity elicited by overactivation of N-methyl-D-aspartate receptors is a well-known characteristic of quinolinic acid-induced neurotoxicity. However, since many experimental evidences suggest that the actions of quinolinic acid also involve reactive oxygen species formation and oxidative stress as major features of its pattern of toxicity, the use of antioxidants as experimental tools against the deleterious effects evoked by this neurotoxin becomes more relevant. In this work, we investigated the effect of a garlic-derived compound and well-characterized free radical scavenger, S-allylcysteine, on quinolinic acid-induced striatal neurotoxicity and oxidative damage. For this purpose, rats were administered S-allylcysteine (150, 300 or 450 mg/kg, i.p.) 30 min before a single striatal infusion of 1 microl of quinolinic acid (240 nmol). The lower dose (150 mg/kg) of S-allylcysteine resulted effective to prevent only the quinolinate-induced lipid peroxidation (P < 0.05), whereas the systemic administration of 300 mg/kg of this compound to rats decreased effectively the quinolinic acid-induced oxidative injury measured as striatal reactive oxygen species formation (P < 0.01) and lipid peroxidation (P < 0.05). S-Allylcysteine (300 mg/kg) also prevented the striatal decrease of copper/zinc-superoxide dismutase activity (P < 0.05) produced by quinolinate. In addition, S-allylcysteine, at the same dose tested, was able to reduce the quinolinic acid-induced neurotoxicity evaluated as circling behavior (P < 0.01) and striatal morphologic alterations. In summary, S-allylcysteine ameliorates the in vivo quinolinate striatal toxicity by a mechanism related to its ability to: (a) scavenge free radicals; (b) decrease oxidative stress; and (c) preserve the striatal activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). This antioxidant effect seems to be responsible for the preservation of the morphological and functional integrity of the striatum.

Age- and region-dependent alterations in the GABAergic innervation in the brain of rats treated with amphetamine.

Mechanisms underlying the pathogenesis of psychotic disorders were explored by monitoring the expression of GABAergic neurons in an animal model. Male rats of postnatal days 21 and 60 were intraperitoneally injected with amphetamine (Amph), 5 mgkg, or saline three times daily for 6 d. After 1-d or 14-d withdrawal from Amph, they were challenged on day 8 (W1d) or on day 21 (W14d) with a single same dosage and then perfused. Immunostaining on the brain sections using an anti-glutamic acid decarboxylase (GAD67) antiserum revealed that the Amph treatment increased the densities of the GAD67-immunoreactive boutons by approx. 36 to 79% above controls in the layers of motor and somatosensory cortices of the W1d juvenile, whereas for those of W14d, the densities resembled controls. For the Amph-treated adults of both W1d and W14d, the GAD67 immunoreactivity increased 56-133% in these layers. In the striatum, the GAD67 densities responded to Amph in a similar manner to the neocortices. However, for the nucleus accumbens, the GAD67 terminals were up-regulated by 22-64% in all Amph-injected rats of both ages. In the hippocampal CA1CA3 region of the Amph-administered juvenile, increases of 24-27% of GAD67 terminals occurred for W1d and W14d animals. By contrast, however, in the W1d Amph-injected adult, there were increases of 42-48% in CA1-CA3, at W14d the GAD67 boutons resembled controls or were reduced. An age-dependent correlation was implicated between behavioural and immunostaining observations. The data support the view that inhibitory regulation is involved in neuronal responses to chronic psychostimulant administration and reflect differential neuronal plasticity among the developing and adult brain regions.

Effects of chronic dermal exposure to nonlethal doses of methyl parathion on brain regional acetylcholinesterase and muscarinic cholinergic receptors in female rats.

The in vivo and in vitro effects of methyl parathion, a phosphorothionate insecticide, on cholinergic neurotransmitter systems in the brain of rats were investigated. Three groups of adult female rats received 0, 0.1, or 1.0 mg/kg methyl parathion via dermal exposure for 95 days. Exposure to 0.1 mg/kg methyl parathion produced inhibition of AChE in the caudate-putamen and thalamic nuclei, whereas 1.0 mg/kg resulted in inhibition of AChE in most brain regions. The same doses of methyl parathion had no effect on [(3)H]QNB binding to muscarinic receptors in the brain regions examined. The in vitro study demonstrated that methyl parathion causes preferential inhibition of AChE and [(3)H]QNB binding in specific brain regions. As an inhibitor of AChE, methyl paraoxon was 1,000-fold more potent than was methyl parathion. Similarly, methyl paraoxon showed brain region-specific inhibition of the enzyme. Generally, the brain stem was highly sensitive to organophosphate-induced inhibition of AChE activity and [(3)H]QNB binding. Because central respiratory neurons gather in the brain stem, preferential effects there and in other brain regions may underlie lethal toxicity of methyl parathion and other organophosphates.

The novel long PDE4A10 cyclic AMP phosphodiesterase shows a pattern of expression within brain that is distinct from the long PDE4A5 and short PDE4A1 isoforms.

In situ hybridisation methods were used to map the distribution of the novel long PDE4A10 isoform in the brain. PDE4A10 distribution was compared to that of the long PDE4A5 isoform and the short PDE4A1 isoform using probes specific for unique sequences within each of these isoforms. Coronal sections of the brain, taken at the level of the olfactory bulb, prefrontal cortex, striatum, thalamus, hippocampus and cerebellum, were analysed. Strongest expression of PDE4A isoforms was found in the olfactory bulb granular layer with high signals also in the piriform cortex, the dentate gyrus and the CA1 and CA2 pyramidal cells. For the two long forms, level general staining was noted throughout the striatum, thalamus and hippocampus but no signal was evident in the cerebellum. The long PDE4A10 and PDE4A5 isoforms localised to essentially the same regions throughout the brain, although PDE4A10 was uniquely expressed in the major island of Calleja. A signal for the short PDE4A1 isoform was found in regions in which the two long isoforms were both expressed, with the exception of the medial nucleus of the amygdala where weak signals for PDE4A5 and PDE4A10 were detected but PDE4A1 was absent. Uniquely, strong signals for PDE4A1 were detected in the glomerular layer of the olfactory bulb, the CA3 pyramidal cell region and the cerebellum; areas where signals for the two long forms were not evident. PDE4A transcripts for both PDE4A5 and PDE4A10 were not apparent in the brain stem and those for PDE4A1 were low. PDE4A isoforms are present in several key areas of the brain and therefore present valid targets for therapeutic interventions. Whilst the two long PDE4A isoforms show a remarkably similar distribution, in at least three regions there is clear segregation between their pattern of expression and that of the PDE4A1 short form. This identifies differential regulation of the expression of PDE4A long and short isoforms. We suggest that specific PDE4A isoforms may have distinct functional roles in the brain, indicating that PDE4A isoform-selective inhibitors may have specific therapeutic and pharmacologic properties.

Regional serotonin metabolism in the brain of transgenic mice lacking monoamine oxidase A.

The effect of a lack of the gene encoding monoamine oxidase A (MAO A) in transgenic Tg8 mice on the activity of tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin (5-HT) biosynthesis, and on the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the midbrain, hypothalamus, hippocampus, striatum, amygdala, and frontal cortex was studied. It was shown that mice with a genetic MAO A knockout differed from mice of the initial C3H/HeJ strain in having a higher level of 5-HT and a lower level of its metabolite, 5-HIAA, in all brain regions but the frontal cortex, where the changes were insignificant. Although the 5-HIAA/5-HT ratio in various brain regions differed considerably, the decrease of the 5-HT oxidative deamination index in Tg8 mice was similar in different brain regions (to 41-45% of control values), with the exception of the frontal cortex, where the decrease of the 5-HIAA/5-HT was somewhat smaller (to 54%). The presence of the remaining 45% +/- 1.9% of the control ratio value indicates rather effective oxidative deamination of 5-HT in MAO A knockout mice and explains the lack of severe behavioral and pathological consequences in MAO A genetic deficiency. An increase of TPH activity in mice lacking MAO A was found in the frontal cortex, hippocampus, and amygdala. No significant changes were found in the striatum, hypothalamus, and midbrain. The data show an effect of the MAO A gene mutation on TPH and indicate a uniform decrease of 5-HT catabolism in different brain regions except for the frontal cortex, which is somewhat more resistant to the lack of MAO A than other brain structures.

Indirubins inhibit glycogen synthase kinase-3 beta and CDK5/p25, two protein kinases involved in abnormal tau phosphorylation in Alzheimer's disease. A property common to most cyclin-dependent kinase inhibitors?

The bis-indole indirubin is an active ingredient of Danggui Longhui Wan, a traditional Chinese medicine recipe used in the treatment of chronic diseases such as leukemias. The antitumoral properties of indirubin appear to correlate with their antimitotic effects. Indirubins were recently described as potent (IC(50): 50-100 nm) inhibitors of cyclin-dependent kinases (CDKs). We report here that indirubins are also powerful inhibitors (IC(50): 5-50 nm) of an evolutionarily related kinase, glycogen synthase kinase-3beta (GSK-3 beta). Testing of a series of indoles and bis-indoles against GSK-3 beta, CDK1/cyclin B, and CDK5/p25 shows that only indirubins inhibit these kinases. The structure-activity relationship study also suggests that indirubins bind to GSK-3 beta's ATP binding pocket in a way similar to their binding to CDKs, the details of which were recently revealed by crystallographic analysis. GSK-3 beta, along with CDK5, is responsible for most of the abnormal hyperphosphorylation of the microtubule-binding protein tau observed in Alzheimer's disease. Indirubin-3'-monoxime inhibits tau phosphorylation in vitro and in vivo at Alzheimer's disease-specific sites. Indirubins may thus have important implications in the study and treatment of neurodegenerative disorders. Indirubin-3'-monoxime also inhibits the in vivo phosphorylation of DARPP-32 by CDK5 on Thr-75, thereby mimicking one of the effects of dopamine in the striatum. Finally, we show that many, but not all, reported CDK inhibitors are powerful inhibitors of GSK-3 beta. To which extent these GSK-3 beta effects of CDK inhibitors actually contribute to their antimitotic and antitumoral properties remains to be determined. Indirubins constitute the first family of low nanomolar inhibitors of GSK-3 beta to be described.

Modifications in brain CaM kinase II after long-term treatment with desmethylimipramine.

The present study investigated the effect of long-term (15 mg/kg for 15 days) and acute (15 mg/kg, single administration) treatment with desmethylimipramine, a tricyclic antidepressant drug, on calcium/calmodulin-dependent protein kinase II (CaMKII), a kinase implicated in the mechanism of antidepressant drug action. Similar to selective and non-selective serotonin reuptake inhibitors, long-term, but not acute, treatment with desmethylimipramine markedly increased the activity of CaMKII in the hippocampal synaptic vesicle fraction (+51.9%). The kinase activity was also increased in the same fraction of frontal cortex (+24.2%) and in the striatum (+45.9%), although in this last area the mechanism appeared to be different because the protein level of the kinase was also markedly increased (+43.7%). However, the effect of treatment was not restricted to the presynaptic kinase, because CaMKII activity was also increased in the total cellular cytosol in cortical areas. The autonomous (calcium-independent) activity of CaMKII was assayed for the first time after antidepressant treatment, and found to be increased in synaptic vesicles of all three areas. These results confirmed the involvement of CaMKII in antidepressant drug action and suggested that modulation of transmitter release is a primary component in the action of psychotropic drugs.

Low selenium diet induces tyrosine hydroxylase enzyme in nigrostriatal system of the rat.

We have studied the effect of a selenium-deficient diet on the nigrostriatal dopaminergic system for 15 and 30 days. The neurochemical analysis demonstrated significant elevations in nigral DA levels after 15 and 30 days of selenium deficiency. The most significant change in striatum was an elevation in dopamine (DA) in 30-day-deficient animals. As a further step, we measured the levels of activity and mRNA expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT). There were significant elevations in all of these parameters in the nigrostriatal system following selenium deficiency at the two time-points studied except for the striatal DA uptake at day 30, which dropped to control levels. Altogether, our results suggest that the decrease in antioxidant capacity due to a selenium deficiency promotes an increase in DA synthesis and turnover, which are clearly associated to the induction of TH. This effect may trigger a positive feed-forward mechanism that could increase the oxidative stress considering the capacity of DA to generate free radicals.

Noradrenergic lesions differentially alter the expression of two subtypes of low Km cAMP-sensitive phosphodiesterase type 4 (PDE4A and PDE4B) in rat brain.

This study examined the effects of selective, central noradrenergic dennervation with 6-hydroxydopamine (6-OHDA) on the expression of type 4 phosphodiesterases (PDE4). Twenty-one days following i.c.v. injection of 6-OHDA (200 microg) hypothalamus, neostriatum, and cerebellum were dissected. Infusion of 6-OHDA reduced norepinephrine (NE) content in all the brain areas examined (to 17%, 76% and 16% of sham-operated controls in hypothalamus, striatum, and cerebellum, respectively). 6-OHDA injections also reduced dopamine levels in hypothalamus (53%) and neostriatum (68%). Administration of desipramine (20 mg/kg, i.p.) 30 min prior to 6-OHDA injection protected neostriatal and cerebellar noradrenergic neurons NE levels (110-122% of the control levels). Desipramine partially attenuated the 6-OHDA-mediated decrease in NE content of hypothalamus, but had little or no effect on either striatal or hypothalamic dopamine (DA) levels. Western blot analysis using a PDE4A-selective antibody revealed three major bands (109 kDa PDE4A5, 102 kDa PDE4AX and 76 kDa PDE4A1) in hypothalamus and striatum. Infusion of 6-OHDA decreased the expression of PDE4A5 and PDE4AX but not of PDE4A1 in hypothalamus, as determined by quantitative Western blotting. Pretreatment of rats with desipramine attenuated the 6-OHDA-induced down-regulation of PDE4A5 and PDE4AX bands in hypothalamus. The PDE4B selective antibody K118 labels 5 major bands in all the brain regions studied. One hundred kDa PDE4B3, 86 kDa PDE4B2 and a 78 kDa PDE4B band was identified using recombinant proteins. Treatment of rats with 6-OHDA resulted in a 52% decrease in the PDE4B3 and 58% decrease in 78 kDa PDE4B variant in hypothalamus; administration of desipramine attenuated the 6-OHDA-induced down-regulation of both PDE4B variants. Neither 6-OHDA nor desipramine altered striatal PDE4A or PDE4B isozymes. In contrast, cerebellar PDE4B3 variant is up-regulated by 6-OHDA treatment and were partially normalized to control values by desipramine pretreatment. These data demonstrate that PDE4 subtypes are differentially regulated by presynaptic noradrenergic activity and may play an important role in the maintaining homeostasis of noradrenergic signal transduction in rat brain.

Functional organisation of the field-L-complex of adult male zebra finches.

Functional maps of auditory response areas were established from multiunit recordings in the caudal telencephalon of male zebra finches. The response criterion was a difference of activity from the spontaneous discharge level. Pure tones and conspecific song were used as stimuli. The auditory part of the caudal telencephalon in zebra finches can be subdivided into six functionally separated centres. The definition of separate areas is based on the existence of tonotopic gradients in each single area and on differences in neural response behaviour between areas. The anatomical area L2a is functionally subdivided into two tonotopic centres. Other areas can be identified by anatomy and function. The borders vary slightly depending on the description method.

Induction of caspase-3-like protease may mediate delayed neuronal death in the hippocampus after transient cerebral ischemia.

Delayed neuronal death after transient cerebral ischemia may be mediated, in part, by the induction of apoptosis-regulatory gene products. Caspase-3 is a newly characterized mammalian cysteine protease that promotes cell death during brain development, in neuronal cultures, and in other cell types under many different conditions. To determine whether caspase-3 serves to regulate neuronal death after cerebral ischemia, we have (1) cloned a cDNA encoding the rat brain caspase-3; (2) examined caspase-3 mRNA and protein expression in the brain using in situ hybridization, Northern and Western blot analyses, and double-labeled immunohistochemistry; (3) determined caspase-3-like activity in brain cell extracts; and (4) studied the effect of caspase-3 inhibition on cell survival and DNA fragmentation in the hippocampus in a rat model of transient global ischemia. At 8-72 hr after ischemia, caspase-3 mRNA and protein were induced in the hippocampus and caudate-putamen (CPu), accompanied by increased caspase-3-like protease activity. In the hippocampus, caspase-3 mRNA and protein were predominantly increased in degenerating CA1 pyramidal neurons. Proteolytic activation of the caspase-3 precursor was detected in hippocampus and CPu but not in cortex at 4-72 hr after ischemia. Double-label experiments detected DNA fragmentation in the majority of CA1 neurons and selective CPu neurons that overexpressed caspase-3. Furthermore, ventricular infusion of Z-DEVD-FMK, a caspase-3 inhibitor, decreased caspase-3 activity in the hippocampus and significantly reduced cell death and DNA fragmentation in the CA1 sector up to 7 d after ischemia. These data strongly suggest that caspase-3 activity contributes to delayed neuronal death after transient ischemia.

Region-specific developmental patterns of atrial natriuretic factor- and nitric oxide-activated guanylyl cyclases in the postnatal frontal rat brain.

In the rat central nervous system, cyclic GMP can be produced by two isoforms of guanylyl cyclase: a cytosolic isoform, which is activated by nitric oxide, and a membrane-bound isoform, activated by atrial natriuretic factor. We studied the development of guanylyl cyclase activity upon maturation of the rat forebrain from postnatal days 4 to 24, using a combined immunocytochemical and biochemical approach. Atrial natriuretic factor-activated particulate guanylyl cyclase activity was found to decrease in the frontal cortex, in the lateral septum and in the piriform cortex upon maturation. A transient expression of atrial natriuretic factor-sensitive guanylyl cyclase activity was observed at postnatal day 8 in the caudate putamen complex, whereas an increase was observed in the lateral olfactory tract from postnatal days 8 to 24. Biochemical and immunocytochemical studies using the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester, or the inhibitor of soluble guanylyl cyclase 1H-[1,2,4]oxadiazolo[4,3-a]quinaloxin-1-one, indicated high levels of endogenous nitric oxide release at postnatal days 4 and 8. This activity decreased strongly in all brain areas examined. From postnatal day 8 onwards, atrial natriuretic factor-responsive cyclic GMP-immunoreactive cells could be characterized as astrocytes, with the exception of those in the the lateral olfactory tract, where the myelinated fibers became cyclic GMP producing. Furthermore, our results on activation of both guanylyl cyclases at postnatal day 8 leads to the suggestion that both isoforms might be found in the same cells. This study shows that there are pronounced differences between various frontal brain areas in the development of the responsiveness of both the particulate and soluble isoforms of guanylyl cyclase, and lends further support to the hypothesis that natriuretic peptides have a role in neuronal growth and plasticity of the rat brain.

Less induced 1-methyl-4-phenylpyridinium ion neurotoxicity on striatal slices from guinea-pigs fed with a vitamin C-deficient diet.

The effect of ascorbic acid depletion on the 1-methyl-4-phenylpyridinium ion (MPP+)-induced neurotoxicity in the dopaminergic system has been tested in guinea-pig striatal slices. Guinea-pigs were divided into three groups and fed on a control diet, ascorbic acid-free diet and ascorbic acid-supplemented diet, respectively. Diets were maintained during 30 days. Striatal slices from ascorbic acid-deficient animals showed the highest levels of dopamine following 25 microM MPP+ treatment; the results from animals under this treatment condition were statistically different from both control and ascorbic acid-supplemented animals under identical experimental conditions. In addition, neurochemical analysis demonstrated that the levels of ascorbic acid and dehydroascorbic acid were highly reduced in striatal tissue from ascorbic acid-deficient animals, thus proving scorbutic conditions in our experimental animals. In view of the higher resistance of the ascorbic acid-deficient animals to the neurotoxicity elicited by MPP+, additional dopaminergic parameters were also measured in striatal tissue from ascorbic acid-deficient animals in the absence of MPP+, including levels of dopamine and its metabolites, tyrosine hydroxylase activity and dopamine uptake, with the aim of finding an explanation for this unexpected result. While dopamine levels and tyrosine hydroxylase activity remained close to control levels, dopamine uptake was significantly reduced in striatal synaptosomes from ascorbic acid-deficient animals as compared with control animals. Since MPP+ is actively accumulated into dopaminergic nerve terminals via the high-affinity dopamine uptake system, this finding could explain the higher resistance of ascorbic acid-deficient animals to the dopamine-depleting effect induced by MPP+ toxicity assayed in striatal slices.

Habrec1, a novel serine/threonine kinase TGF-beta type I-like receptor, has a specific cellular expression suggesting function in the developing organism and adult brain.

Members of the TGF-beta superfamily signal through a dual receptor system consisting of a type II receptor protein kinase that binds the ligand, after which this complex associates with a type I receptor to mediate intracellular signaling. In mammals, six type I and five type II receptors mediating responses to different TGF-beta family members have been identified to date. Using primers from conserved regions of the protein kinase domain of the serine/threonine kinase receptors in a low-stringency polymerase chain reaction-based screening procedure, and deselecting known receptors with colony hybridization, we now report cloning a novel receptor member. The novel receptor was found in a cDNA library prepared from the habenular nucleus area and was designated Habrec1. Although only a partial sequence is available, it fits the criteria for a TGF-beta type I serine/threonine kinase receptor. In situ hybridization of Habrec1 reveals mRNA expression in several distinct areas of the developing central nervous system, including cortex cerebri, cerebellum, hippocampus, striatum, and thalamic nuclei. Expression is also seen in the anterior pituitary. In the periphery, strong expression prenatally includes brown fat, the gastrointestinal tract, liver, pancreas, thymus, and nasal cavity epithelium. In the adult brain Habrec1 mRNA is prominently found in cerebellum, cortex cerebri, and striatum, but at lower levels in several additional areas. We conclude that Habrec1 is a member of the TGF-beta type I receptor family with expression patterns in the developing animal, suggesting specific functions in and outside the nervous system, and in the adult CNS, suggesting roles in both cortical and subcortical brain circuitry.

D2 dopamine receptor antisense increases the activity and mRNA of tyrosine hydroxylase and aromatic L-amino acid decarboxylase in mouse brain.

A D2 dopamine receptor antisense oligodeoxynucleotide was administered intracerebrovetricularly to mice twice on the first day and then once daily for 2 days. The animals were killed 2 h after the last injection, and tyrosine hydroxylase and aromatic L-amino acid decarboxylase activities assayed in the corpus striatum, olfactory tubercle and frontal cortex. Tyrosine hydroxylase activity increased in corpus striatum but not in the olfactory tubercle or in the frontal cortex, while the activity of aromatic L-amino acid decarboxylase increased in all three brain regions. The treatment with the antisense oligomer also elevated the mRNA levels for the two enzymes in the midbrain. In contrast, repeated injection of a vehicle or a random oligomer was without effect on enzyme activity or mRNA D2 antisense oligodeoxynucleotides appear to be selective tools to investigate the role of D2 dopamine receptors in brain.

Neurochemical characteristics of the rat neostriatum and motor cortex after the development of a unilateral manipulatory reflex.

Indicators of the activity of acetylcholinesterase (ACE), 5'-nucleotidase (NT), adenylate cyclase (AC) in the sensorimotor cortex and the neostriatum (NS) of the right and left cerebral hemispheres of control rats and rats trained to perform a food-procuring movement by pressing against an obstacle with the forelimb. An identical level of the averaged bilateral values of the activity of NT and AC in both of the structures in question and an increased ACE activity in the NS were found in the control animals. After the development of a manipulatory skill, the activity of AC decreased in the cortex and the NS in the presence of unchanged ACE activity, while NT activity decreased in the cortex and increased in the NS. The bilateral values of the activity of the enzymes differed significantly in well and poorly trained rats. At the same time, the activity of the enzymes was similar in character in the dominant and subdominant hemispheres for each group of animals. Overall the neurochemical changes obtained can be regarded as specific correlates of the developed unilateral manipulatory reactions that are characteristic for the structures in question of both cerebral hemispheres.

Choline acetyltransferase activity is reduced in rat nucleus accumbens after unlimited access to self-administration of cocaine.

Choline acetyltransferase (ChAT) activity was measured in discrete areas of rat brain after chronic, unlimited access to self-administration of cocaine. Mean activity of ChAT was reduced by approximately 30% in the nucleus accumbens, both on the last day of cocaine access and after 3 weeks cocaine withdrawal. These data suggest that chronic cocaine exposure might inhibit nucleus accumbens cholinergic neurones which could underlie some of the behavioral effects of cocaine.

Isolation and characterization of a zebra finch aromatase cDNA: in situ hybridization reveals high aromatase expression in brain.

The brain regions controlling song are much larger in male than in female zebra finches. This sex difference is thought to arise developmentally when the male's brain is exposed to higher levels of estrogen. The synthesis of estrogen from androgen is catalyzed by aromatase, a key enzyme implicated in song development in the zebra finch. To study the role of estrogen synthesis in the organization of brain regions responsible for song, a cDNA encoding aromatase was isolated from a zebra finch ovarian cDNA library. The 3188 bp cDNA contains a 1527 bp open reading frame with 5' and 3' untranslated regions of 116 bp and 1545 bp, respectively. The deduced polypeptide is 509 amino acids in length, and is highly homologous to aromatases reported for chicken (92%), human (72%), mouse (70%), rat (69%) and trout (53%). Northern blot analysis revealed 5.4 kb, 4.8 kb and 3.2 kb aromatase mRNAs in brain and ovary. In situ hybridization histochemistry revealed the expression of aromatase mRNA in ovarian thecal cells of some, but not all, follicles, suggesting that aromatase gene expression is regulated during follicular maturation. In the adult brain, the distribution of aromatase mRNA was surprisingly widespread, and included the preoptic area, hypothalamus, hippocampus and neostriatum. By contrast, little aromatase mRNA expression was noted in the song nuclei (HVC, RA, area X). This study, the first description of aromatase mRNA expression by in situ hybridization in the brain of any species, identifies a surprisingly large number of cells that express aromatase mRNA in the zebra finch telencephalon. This pattern may be a unique feature of all songbirds.