Vitamin D3 favorable outcome on recognition memory and prefrontal cortex expression of choline acetyltransferase and acetylcholinesterase in experimental model of chronic high-fat feeding.

Aim of the study: High-fat diet (HFD) consumption and insufficient vitamin D levels are globally increasing phenomena. The present study assessed the effect of chronic HFD feeding with and without vitamin D supplementation on recognition memory and prefrontal cortex expression of choline acetyltransferase (CAT) and acetylcholinesterase (Achase).Materials and methods: Forty male Wistar rats were subjected to four dietary regimens (n = 10); control diet (10% fat), control + vitamin D3, high-fat diet (HFD 45% fat) and HFD + vitamin D3 for 6 months. Rats were tested for the novel object recognition test, and their prefrontal cortices were assessed for expression of CAT and Achase.Results: Recognition memory was impaired in HFD-fed rats compared to control rats as evidenced by significantly decreased discrimination index in the novel object recognition test. Moreover, CAT expression was significantly decreased while Achase expression was significantly increased in the prefrontal cortex of HFD-fed rats. Vitamin D3 supplementation with HFD significantly increased the exploration of the novel object and the discrimination index and attenuated the alterations in the prefrontal cortex CAT and Achase expression.Conclusions: The present findings support the potential effect of vitamin D on recognition memory and cholinergic transmission in the prefrontal cortex and add to the pathophysiology of HFD consumption.

Cerebral MAO Activity Is Not Altered by a Novel Herbal Antidepressant Treatment.

Inhibition of monoamine oxidase (MAO)-A/B can ameliorate depressive- and anxiety-related symptoms via increase of monoamine extracellular levels. However, such inhibition can also instigate hypertensive response following exposure to dietary tyramine (i.e., "the cheese effect"). Novel herbal treatment (NHT) is an herbal formula that has been demonstrated to reduce depressive- and anxiety-like symptoms in pre-clinical studies. The aim of the current study was to examine whether the therapeutic potential of NHT is underlain by inhibition of MAO-A/B and whether NHT poses a risk for tyramine hyper-potentiation. Unpredictable chronic mild stress (UCMS)-exposed mice and naïve mice were treated for 3 weeks with NHT (30 mg/kg; i.p.), the selective serotonin reuptake inhibitor (SSRI) escitalopram (15 mg/kg; i.p.), or saline. Subsequently, MAO-A/B activities in the hypothalamus, striatum, and prefrontal cortex (PFC) were assessed. Exposure to UCMS led to significant increases in both MAO-A and MAO-B activities in the hypothalamus (p < 0.001) and in the PFC (p < 0.01 for MAO-A; p < 0.001 for MAO-B). Neither NHT nor escitalopram had any notable effects. Treatment with NHT was supported as safe in terms of risk for inducing a hypertensive response. The antidepressant- and anxiolytic-like effects of NHT are mediated via pathways other than MAO-A/B inhibition.

Brain region specific methylation and Sirt1 binding changes in MAOA promoter is associated with sexual dimorphism in early life stress induced aggressive behavior.

The maladaptive form of aggressive behavior confers risk for violence and criminal incidences with profound impact on society. Although considerable research has been devoted to elucidate the etiology of aggression, molecular correlates of sex differences remains largely unexplored. Also, little attention has been given to whether males and females respond differently to similar causal factor of aggression. Here, we show the possible association of brain region specific neural activity (c-Fos expression) and monoamine oxidase A (MAOA) epigenetic state with sexual dimorphism in peripubertal stress (PPS) induced adulthood aggression. While PPS adult males exhibited escalated aggression, females spent maximal time in social exploration. c-Fos expression was brain region and sex specific. In the PPS adult cohort, only males showed elevated c-Fos expression in the prefrontal cortex, indicative of their hyper-responsive behavior. MAOA expression and enzyme activity was reduced in hypothalamus and increased in prefrontal cortex of hyper-aggressive male mice. Investigation into the underlying mechanisms revealed hypomethylation in prefrontal cortex and hypermethylation in hypothalamus of MAOA promoter negatively correlating with the expression pattern. On the other hand, binding of Sirt1 to MAOA promoter was diametrically opposite being increased in prefrontal cortex and reduced in hypothalamus. In females, neither expression nor epigenetic state of MAOA gene was significantly altered between control and PPS adult mice. Our study revealed novel epigenetic correlates of sexual dimorphism in stress induced aggressive psychopathology. However, given the multi-factorial nature with environmental influences, further studies are warranted to uncover the biological hub.

The preventive effects of ascorbic acid supplementation on locomotor and acetylcholinesterase activity in an animal model of schizophrenia induced by ketamine.

Studies have shown that schizophrenic patients seem to have nutritional deficiencies. Ascorbic acid (AA) has an important antioxidant effect and neuromodulatory properties. The aim of this study was to evaluate the effects of AA on locomotor activity and the acetylcholinesterase activity (AChE) in an animal model of schizophrenia (SZ). Rats were supplemented with AA (0.1, 1, or 10 mg/kg), or water for 14 days (gavage). Between the 9th and 15th days, the animals received Ketamine (Ket) (25 mg/kg) or saline (i.p). After the last administration (30 min) rats were subjected to the behavioral test. Brain structures were dissected for biochemical analysis. There was a significant increase in the locomotor activity in Ket treated. AA prevented the hyperlocomotion induced by ket. Ket also showed an increase of AChE activity within the prefrontal cortex and striatum prevented by AA. Our data indicates an effect for AA in preventing alterations induced by Ket in an animal model of SZ, suggesting that it may be an adjuvant approach for the development of new therapeutic strategies within this psychiatric disorder.

Effects of hydrogen-rich water on depressive-like behavior in mice.

Emerging evidence suggests that neuroinflammation and oxidative stress may be major contributors to major depressive disorder (MDD). Patients or animal models of depression show significant increase of proinflammatory cytokine interleukin-1ß (IL-1ß) and oxidative stress biomarkers in the periphery or central nervous system (CNS). Recent studies show that hydrogen selectively reduces cytotoxic oxygen radicals, and hydrogen-rich saline potentially suppresses the production of several proinflammatory mediators. Since current depression medications are accompanied by a wide spectrum of side effects, novel preventative or therapeutic measures with fewer side effects might have a promising future. We investigated the effects of drinking hydrogen-rich water on the depressive-like behavior in mice and its underlying mechanisms. Our study show that hydrogen-rich water treatment prevents chronic unpredictable mild stress (CUMS) induced depressive-like behavior. CUMS induced elevation in IL-1ß protein levels in the hippocampus, and the cortex was significantly attenuated after 4 weeks of feeding the mice hydrogen-rich water. Over-expression of caspase-1 (the IL-1ß converting enzyme) and excessive reactive oxygen species (ROS) production in the hippocampus and prefrontal cortex (PFC) was successfully suppressed by hydrogen-rich water treatment. Our data suggest that the beneficial effects of hydrogen-rich water on depressive-like behavior may be mediated by suppression of the inflammasome activation resulting in attenuated protein IL-1ß and ROS production.

Oxidant/antioxidant effects of chronic exposure to predator odor in prefrontal cortex, amygdala, and hypothalamus.

The incidence of anxiety-related diseases is increasing these days, hence there is a need to understand the mechanisms that underlie its nature and consequences. It is known that limbic structures, mainly the prefrontal cortex and amygdala, are involved in the processing of anxiety, and that projections from prefrontal cortex and amygdala can induce activity of the hypothalamic-pituitary-adrenal axis with consequent cardiovascular changes, increase in oxygen consumption, and ROS production. The compensatory reaction can include increased antioxidant enzymes activities, overexpression of antioxidant enzymes, and genetic shifts that could include the activation of antioxidant genes. The main objective of this study was to evaluate the oxidant/antioxidant effect that chronic anxiogenic stress exposure can have in prefrontal cortex, amygdala, and hypothalamus by exposition to predator odor. Results showed (a) sensitization of the HPA axis response, (b) an enzymatic phase 1 and 2 antioxidant response to oxidative stress in amygdala, (c) an antioxidant stability without elevation of oxidative markers in prefrontal cortex, (d) an elevation in phase 1 antioxidant response in hypothalamus. Chronic exposure to predator odor has an impact in the metabolic REDOX state in amygdala, prefrontal cortex, and hypothalamus, with oxidative stress being prevalent in amygdala as this is the principal structure responsible for the management of anxiety.

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.

Regionally selective activation of ERK and JNK in morphine paradoxical hyperalgesia: a step toward improving opioid pain therapy.

In addition to analgesia, opioid agonists may increase pain sensitivity under different conditions varying dose and administration pattern. While opioid hyperalgesia induced by tolerance and withdrawal is largely studied, little is known on the mechanisms underlying ultra-low dose morphine hyperalgesia. This pronociceptive response appears to play an opposing role in morphine analgesia and might have clinical relevance. Ultra-low dose morphine elicited thermal hyperalgesia through activation of µ opioid receptors. To elucidate the intracellular mechanism of morphine nociceptive behaviour, we investigated the mitogen-activated protein kinase (MAPK), crucial pathways in pain hypersensitivity. The catalytic activity of extracellular signal-regulated kinase (ERK), p38, c-Jun-N-terminal kinase (JNK), upstream modulators and transcription factors was investigated in the mouse periaqueductal grey matter (PAG), thalamus and prefrontal cortex by western blotting. Ultra-low dose morphine intensively increased pERK1 contents in the PAG and cortex and, to a lesser extent, increased cortical ERK2 and JNK phosphorylation. No involvement of p38 was detected. Morphine exposure also increased phosphorylation of cortical c-Jun whereas levels of phosphorylated cAMP response element-binding protein (CREB) remained unmodified. Blockade of protein kinase C (PKC) prevented increases in phosphorylation showing a PKC-dependent mechanism of activation. Pharmacological inhibitors of PKC, ERK, and JNK activity prevented morphine hyperalgesia. No modulation of MAPK and transcription factors' activity was detected in the thalamus. These results support the concept that selective activation of ERK and JNK on descending pathways plays an important role in ultra-low dose morphine hyperalgesia. The modulation of these signalling processes might improve pain management with opiate analgesics.

[Effect of electroacupuncture intervention at different time-points in a day on expression of c-fos and neuronal nitric oxide synthase in medial prefrontal cortex in ketamine addiction rats].

UNLABELLED: To observe the effects of electroacupuncture(EA) stimulation of "Zusanli"(ST 36) and "Sanyinjiao"(SP 6) at different time-points of a day on the expression of c-fos and neuronal nitric oxide synthase (nNOS) in the medial prefrontal cortex (mPFC) in rats with ketamine addiction. METHODS: A total of 56 SD rats were randomized into control group, saline group, model group and EA group. The EA group was further divided into Zi-shi (23 : 00), Mao-shi (05 : 00), Wu-shi (11 : 00) and You-shi (17 : 00) subgroups (n = 8 in each group or subgroup). Ketamine addiction model was established by intraperitoneal administration of ketamine (100 mg/kg), once a day for 7 days. EA (2 Hz, 3 V) was applied to unilateral "Zusanli" (ST 36) and "Sanyinjiao" (SP 6) acupoints for 30 min, once daily for 7 days. The expression of c-fos and nNOS in the mPFC was detected by immunohistochemistry. RESULTS: Following EA intervention for 7 days, the animals' daily life activities including body stretching, standing, jumping, circling, falling on the back and fur-licking in the EA group (Wu-shi and You-shi subgroups) were close to those of the normal control and saline groups, being much better than the model group. Compared with the normal control group and saline group, the expression levels of c-fos and nNOS in the mPFC in the model group were significantly upregulated (P < 0.05). Compared with the model group, the expression levels of both c-fos and nNOS were considerably down-regulated in the Wu-shi (11 : 00) and You-shi (17 : 00) subgroups (P < 0.05), rather than in the Zi-shi (23 : 00) and Mao-shi (05 : 00) subgroups (P > 0.05). CONCLUSION: EA of ST 36 and SP 6 at 11 : 00 and 17 : 00 can decrease the expression o fc-fos and nNOS in the mPFC in ketamine addiction rats, which may contribute to its effects in improving the rats' behavior activity.

Sexual metabolic differences in the rat limbic brain.

BACKGROUND: There is actually limited evidence about the influence of estrogens on neuronal energy metabolism or functional cerebral asymmetry. In order to evaluate this relationship, eight male and sixteen female adult Wistar rats, divided into estrus and diestrus phase, were used to measure basal neuronal metabolic activity in some of the structures involved in the Papez circuit, using cytochrome c oxidase (C.O.) histochemistry. METHOD: We used C.O. histochemistry because cytochrome oxidase activity can be considered as a reliable endogenous marker of neuronal activity. RESULTS: We found higher C.O. activity levels in diestrus as compared to estrus and male groups in the prefrontal cortex and thalamus. Conversely, neuronal oxidative metabolism was significantly higher in estrus than in diestrus and male groups in the dorsal and ventral hippocampus (CA1 and CA3) and in the mammillary bodies. However, no hemispheric functional lateralization was found in estrus, diestrus or male groups by C.O. activity. CONCLUSIONS: These results suggest a modulatory effect of estrogens on neuronal oxidative metabolism.

'Roid rage in rats? Testosterone effects on aggressive motivation, impulsivity and tyrosine hydroxylase.

In humans and animals, anabolic-androgenic steroids (AAS) increase aggression, but the underlying behavioral mechanisms are unclear. AAS may increase the motivation to fight. Alternatively, AAS may increase impulsive behavior, consistent with the popular image of 'roid rage. To test this, adolescent male rats were treated chronically with testosterone (7.5mg/kg) or vehicle and tested for aggressive motivation and impulsivity. Rats were trained to respond on a nose-poke on a 10 min fixed-interval schedule for the opportunity to fight in their home cage with an unfamiliar rat. Although testosterone increased aggression (6.3±1.3 fights/5 min vs 2.4±0.8 for controls, p<0.05), there was no difference in operant responding (28.4±1.6 nose-pokes/10 min for testosterone, 32.4±7.0 for vehicle). This suggests that testosterone does not enhance motivation for aggression. To test for impulsivity, rats were trained to respond for food in a delay-discounting procedure. In an operant chamber, one lever delivered one food pellet immediately, the other lever gave 4 pellets after a delay (0, 15, 30 or 45 s). In testosterone- and vehicle-treated rats, body weights and food intake did not differ. However, testosterone-treated rats chose the larger, delayed reward more often (4.5±0.7 times in 10 trials with 45 s delay) than vehicle controls (2.5±0.5 times, p<0.05), consistent with a reduction in impulsive choice. Thus, although chronic high-dose testosterone enhances aggression, this does not include an increase in impulsive behavior or motivation to fight. This is further supported by measurement of tyrosine hydroxylase (TH) by Western immunoblot analysis in brain regions important for motivation (nucleus accumbens, Acb) and executive function (medial prefrontal cortex, PFC). There were no differences in TH between testosterone- and vehicle-treated rats in Acb or PFC. However, testosterone significantly reduced TH (to 76.9±3.1% of controls, p<0.05) in the caudate-putamen, a brain area important for behavioral inhibition, motor control and habit learning.

Effect of repeated restraint on homotypic stress-induced nitric oxide synthases expression in brain structures regulating HPA axis.

BACKGROUND: Restraint stress (RS) markedly increases interleukin 1-ß (IL-1ß) generation in brain structures involved in hypothalamic-pituitary adrenocortical (HPA) axis regulation. The IL-1ß-induced transient stimulation of HPA axis activity was parallel in time and magnitude to respective changes in regulation of HPA activity. In the present experiment the expression of neuron al and inducible nitric oxide synthase (nNOS and iNOS) were investigated in prefrontal cortex, hippocampus and hypothalamus in response to acute restraint stress in control and prior repeatedly restrained rats. METHODS: Experiments were performed on male Wistar rats which were exposed to 10 min restraint stress or restrained twice a day for 3 days, and 24 h after the last stress period exposed to homotypic stress for 10 min. After rapid decapitation at 0, 1, 2 and 3 h after cessation of stress, trunk blood was collected and prefrontal cortex, hippocampus and hypothalamus were excised and frozen. Interleukin-1ß, adrenocorticotropic hormone (ACTH) and corticosterone (CORT) levels were determined in plasma using commercially available kits and neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in brain structure samples were analyzed by western blot procedure. RESULTS: Prior repeated restraint stress enhanced the acute restraint stress induced increase in IL-1ß levels in all three structures examined. Restraint stress for 10 min moderately decreased nNOS level in prefrontal cortex in control rats, augmented this level in hippocampus and markedly increased nNOS level in hypothalamus. Restraint itself significantly decreased iNOS level in prefrontal cortex, while it enhanced iNOS level in hippocampus and hypothalamus. Prior restraint stress for 3 days enhanced the nNOS level in prefrontal cortex and hippocampus and did not substantially affect nNOS levels response in hypothalamus. Repeated restraint stress considerably augmented the iNOS levels in both prefrontal cortex, hippocampus and hypothalamus induced by followed homotypic stress. CONCLUSION: These results indicate that during restraint stress nNOS regulate formation of low amount of NO and the high-output generation of NO is effected by inducible isoform of nitric oxide synthase. Prior repeated stress significantly enhances the homotypic stress-induced nNOS and iNOS responses.

Inhibitory effect of curcuminoids on acetylcholinesterase activity and attenuation of scopolamine-induced amnesia may explain medicinal use of turmeric in Alzheimer's disease.

Curcuminoids (a mixture of curcumin, bisdemethoxycurcumin and demethoxycurcumin) share vital pharmacological properties possessed by turmeric, a well known curry spice, considered useful in Alzheimer's disease (AD). The aim of this study was to evaluate if curcuminoids possess acetylcholinesterase (AChE) inhibitory and memory enhancing activities. The in-vitro and ex-vivo models of AChE inhibitory activity were used along with Morris water maze test to study the effect on memory in rats. Curcuminoids inhibited AChE in the in-vitro assay with IC(50) value of 19.67, bisdemethoxycurcumin 16.84, demethoxycurcumin 33.14 and curcumin 67.69 microM. In the ex-vivo AChE assay, curcuminoids and its individual components except curcumin showed dose-dependent (3-10 mg/kg) inhibition in frontal cortex and hippocampus. When studied for their effect on memory at a fixed dose (10 mg/kg), all compounds showed significant (p<0.001) and comparable effect in scopolamine-induced amnesia. These data indicate that curcuminoids and all individual components except curcumin possess pronounced AChE inhibitory activity. Curcumin was relatively weak in the in-vitro assay and without effect in the ex-vivo AChE model, while equally effective in memory enhancing effect, suggestive of additional mechanism(s) involved. Thus curcuminoids mixture might possess better therapeutic profile than curcumin for its medicinal use in AD.

Cocaine alters catalase activity in prefrontal cortex and striatum of mice.

Catalase is one of the enzymes that convert hydrogen peroxide (H2O2) to H2O presenting a protective role against free radicals. In this study, catalase activity was determined in homogenates of striatum (ST) and prefrontal cortex (PFC) in order to examine the participation of oxidative stress (OS) on cocaine actions in mice brain. Male Swiss mice were injected (i.p.) with cocaine at low (10 and 30 mg/kg) and high doses (90 mg/kg), and observed for 1 h. After cocaine overdose (90 mg/kg) some animals presented only status epilepticus (SE) while others died after seizures. These animals were dissected and divided in two groups, SE and death. Catalase activity was also determined after pretreatment with the anticonvulsant drug, diazepam, alone or injected before cocaine 90 mg/kg, and after seizures induced by a high dose of bupropion, a known inhibitor of NE and DA reuptake used for comparison. Results showed a decrease in catalase activity of the PFC and ST after SE and death induced by cocaine and bupropion overdoses. Cocaine at low doses decreased the enzyme activity only in ST. Diazepam treatment alone and before cocaine overdose did not interfere with catalase activity. This reduction in catalase activity may reflect an increase in H2O2 content in PFC and ST. Previous data reports that H2O2 inhibits dopamine transporter activity, suggesting that the decrease in catalase activity may potentiate the toxic mechanism of drugs that inhibit monoamines reuptake. As far as we know, this is the first report showing an involvement of OS in the cocaine's central mechanism of action.

Hypericum perforatum L (St John's wort) preferentially increases extracellular dopamine levels in the rat prefrontal cortex.

The effects of hydro-alcoholic extracts of Hypericum perforatum L on extracellular serotonin (5-HT), noradrenaline (NA) and dopamine (DA) levels and the acidic metabolites (3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxy-3-indoleacetic acid (5-HIAA)) were examined by in vivo microdialysis in the prefrontal cortex of awake rats. Thus, a single dose (60 mg kg(-1) i.p. or 300 mg kg(-1) p.o.) of H. perforatum increased DA concentrations to 165 and 140% of control values, respectively, and increased locomotor activity in nonhabituated rats. DOPAC and HVA levels were markedly reduced. 5-HT concentrations were elevated only moderately, while the NA levels were not affected by any treatment. The whole-tissue analysis revealed that hypericum increased, whereas the monoamine oxidase (MAO) A/B inhibitor phenelzine decreased DA and 5-HT turnover. The present data indicate that the mechanism of action of hypericum extract in vivo is more complex than the inhibition of monoamine reuptake or metabolism observed in vitro. The finding of preferential enhancement of DA transmission is in agreement with human studies measuring DA-mediated neuroendocrine responses.

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 action of brofaromine on rat brain MAO-A and MAO-B.

1. Brofaromine (CGP 11,305 A) belongs to a new generation of monoamine oxidase (MAO) inhibitors. These compounds induce short, reversible and selective inhibition of brain MAO of type A. 2. The aim of this work is to study monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B) activities of several rat brain regions after increasing doses of brofaromine. 3. Brofaromine inhibits MAO-A activities in a dose dependent manner in all brain regions examined. 4. The largest reduction was found in hippocampal formation, striatum and prefrontal cortex respectively. ID50 is 2 times lower in hippocampus than in remaining brain. 5. Brofaromine does not inhibit MAO-B activities in the different regions examined. 6. Brofaromine is a very selective inhibitor of rat brain MAO-A with a preferential action on telencephalic monoaminergic nerve terminals.

Decrease of immunoreactive catalase protein in specific areas of ageing rat brain.

The activity of catalase, the main enzyme responsible for detoxification against hydrogen peroxide, decreases in specific brain areas of aged rats. The reduction of enzyme activity appears to be the consequence of a decreased protein expression rather than an impaired function of the native enzyme. In fact, diminution of the immunoreactive protein parallels enzyme activity decrease. Since the extent of decrease of both activity and protein content was observed to be area dependent, we hypothesise that this phenomenon may underlie, at least in part, the increased susceptibility of specific brain regions to oxidative insults observed in pathological situations related to ageing.

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.

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.