Treadmill exercise alters histone acetyltransferases and histone deacetylases activities in frontal cortices from wistar rats.

Studies have pointed out the relationship between neuroprotective exercise effects and epigenetic mechanisms on the hippocampus. Considering the role of frontal cortex on brain functions, we investigated the impact of different exercise protocols on enzymatic system involved with histone acetylation status, histone acetyltransferases (HATs), and histone desacetylases (HDACs) in frontal cortices from Wistar rats. Male Wistar rats aged 3 months were submitted to a single session or a daily running protocol during 2 weeks. The single session enhanced HAT activity, while the moderate daily exercise protocol reduced the HDAC activity. Our results indicate that frontal cortex is susceptible to epigenetic modulation following exercise and that both exercise protocols seem to induce a histone hyperacetylation condition in this brain area.

Increase in medial frontal cortex ERK activation following the induction of apomorphine sensitization.

Repeated high dose injections of the direct acting D1/D2 agonist apomorphine (APO) induces context specific behavioral sensitization. We assessed the effects of 2.0 mg/kg APO on open-field locomotor responses of rats over a 30 min period following either single or five daily APO injections. Acute injections increased locomotor activity, which was markedly increased in rats given 5 daily APO injections. This progressive increase in locomotion during the repeated APO treatments is indicative of behavioral sensitization. Immediately following the open-field test for the acute and the fifth apomorphine injection, the animals were euthanized and their brain tissue was prepared for immunohistochemistry. ERK immunoreactive nuclei in the medial prefrontal cortex (PFC), nucleus accumbens (NAcc), amygdala (AMYG) and lateral hypothalamus (LH) were quantified. The acute apomorphine injections increased ERK in all brain areas as compared to vehicle. Following the fifth apomorphine injection, ERK significantly increased in the PFC, decreased in the amygdala but was unchanged in the LH and NAcc. The selective increase in ERK activity in the PFC associated with behavioral sensitization, points to a possible pivotal role of the dopamine projection to the medial frontal cortex in the mediation of neural plasticity, considered to underlie the sensitization processes induced by dopaminergic drugs.

Histone deacetylase activity is altered in brain areas from aged rats.

It has been described that histone acetylation levels are decreased in several cellular and in vivo neurodegeneration models as well as in normal brain aging, although the impact of the aging process on histone deacetylases (HDAC) activity yet remains poorly understood. Therefore, our aim was to evaluate the effect of the aging process on HDAC activity in hippocampi and frontal cortices from 3 and 18-months-old Wistar rats. The animals were decapitated at different times of day, in the early morning and in afternoon. HDAC activity was increased in hippocampus from the aged group. Besides, the hippocampal HDAC activity was also significantly increased in early morning. A significant interaction between age and time of the day was observed in frontal cortices, given that the HDAC activity was higher in early morning in the aged group. These data support the hypothesis that the aging-related dysfunction may be related, at least in part, to acetylation imbalance through HDAC activity in rat brain.

Is oxidative stress in mice brain regions diminished by 2-[(2,6-dichlorobenzylidene)amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile?

2-[(2,6-Dichlorobenzylidene)amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile, 5TIO1, is a new 2-aminothiophene derivative with promising pharmacological activities. The aim of this study was to evaluate its antioxidant activity in different areas of mice central nervous system. Male Swiss adult mice were intraperitoneally treated with Tween 80 dissolved in 0.9% saline (control group) and 5TIO1 (0.1, 1, and 10 mg kg(-1)). Brain homogenates-hippocampus, striatum, frontal cortex, and cerebellum-were obtained after 24 h of observation. Superoxide dismutase and catalase activities, lipid peroxidation and nitrite content were measured using spectrophotometrical methods. To clarify the 5TIO1's mechanism on oxidative stress, western blot analysis of superoxide dismutase and catalase was also performed. 5TIO1 decreased lipid peroxidation and nitrite content in all brain areas and increased the antioxidant enzymatic activities, specially, in cerebellum. The data of Western blot analysis did not demonstrate evidence of the upregulation of these enzymes after the administration of this compound. Our findings strongly support that 5TIO1 can protect the brain against neuronal damages regularly observed during neuropathologies.

In vitro studies of the influence of glutamatergic agonists on the Na+,K(+)-ATPase and K(+)-p-nitrophenylphosphatase activities in the hippocampus and frontal cortex of rats.

BACKGROUND: The overstimulation of excitatory glutamatergic neurotransmission and the inhibition of Na(+),K(+)-ATPase enzymatic activity have both been implicated in neurotoxicity and are possibly related to the pathogenesis of epilepsy and neurodegenerative disorders. In the present study, we investigated whether glutamatergic stimulation by the glutamatergic agonists glutamate, α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA), kainate and N-methyl-d-aspartate (NMDA) modulates the Na(+),K(+)-ATPase and the K(+)-p-nitrophenylphosphatase activities in the crude synaptosomal fraction of the hippocampus and the frontal cortex of rats. RESULTS: Our results demonstrated that these glutamatergic agonists did not influence the activities of Na(+),K(+)-ATPase or K(+)-p-nitrophenylphosphatase in the brain structures analyzed. Assays with lower concentrations of ATP to analyze the preferential activity of the Na(+),K(+)-ATPase isoform with high affinity for ATP did not show any influence either. CONCLUSIONS: These findings suggest that under our experimental conditions, the stimulation of glutamatergic receptors does not influence the kinetics of the Na(+),K(+)-ATPase enzyme in the hippocampus and frontal cortex.

Cocaine administration increases angiotensin I-converting enzyme (ACE) expression and activity in the rat striatum and frontal cortex.

Some central effects of cocaine administration seem to be related to angiotensin II (Ang II) or its metabolites. Nonetheless, it is still an open question whether or not the levels of angiotensin I-converting enzyme (ACE), the main Ang II generating enzyme, are modified by cocaine administration. To evaluate the effect of acute and subchronic cocaine administration on ACE activity and mRNA expression, male rats were randomly assigned to saline or cocaine group. Acute and subchronic cocaine administration induced a significant increase in ACE activity and mRNA expression in the frontal cortex and striatum but not in the hippocampus. These results suggest that some of the Ang II related effects of cocaine upon the central nervous system can be mediated by changes on the expression and activity of ACE in the striatum and frontal cortex.

Inhibition of phospholipase A2 in rat brain decreases the levels of total Tau protein.

The microtubule-associated protein Tau promotes the assembly and stability of microtubules in neuronal cells. Six Tau isoforms are expressed in adult human brain. All six isoforms become abnormally hyperphosphorylated and form neurofibrillary tangles in Alzheimer disease (AD) brains. In AD, reduced activity of phospholipase A(2) (PLA(2)), specifically of calcium-dependent cytosolic PLA(2) (cPLA(2)) and calcium-independent intracellular PLA(2) (iPLA(2)), was reported in the cerebral cortex and hippocampus, which positively correlated with the density of neurofibrillary tangles. We previously demonstrated that treatment of cultured neurons with a dual cPLA(2) and iPLA(2) inhibitor, methyl arachidonyl fluorophosphonate (MAFP), decreased total Tau levels and increased Tau phosphorylation at Ser(214) site. The aim of this study was to conduct a preliminary investigation into the effects of in vivo infusion of MAFP into rat brain on PLA(2) activity and total Tau levels in the postmortem frontal cortex and dorsal hippocampus. PLA(2) activity was measured by radioenzymatic assay and Tau levels were determined by Western blotting using the anti-Tau 6 isoforms antibody. MAFP significantly inhibited PLA(2) activity in the frontal cortex and hippocampus. The reactivity to the antibody revealed three Tau protein bands with apparent molecular weight of close to 40, 43 and 46 kDa in both brain areas. MAFP decreased the 46 kDa band intensity in the frontal cortex, and the 43 and 46 kDa band intensities in the hippocampus. The results indicate that in vivo PLA(2) inhibition in rat brain decreases the levels of total (nonphosphorylated plus phosphorylated) Tau protein and corroborate our previous in vitro findings.

Choline acetyltransferase and acetylcholinesterase activities are reduced in rat striatum and frontal cortex after pilocarpine-induced seizures.

In the present study we investigated the alterations on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in rat striatum and frontal cortex caused by pilocarpine-induced seizures. Wistar rats were treated with 0.9% saline (i.p., control group), with the association of 0.9% saline (i.p.) plus pilocarpine (400mg/kg, i.p.), 30 min before of administration of saline (pilocarpine group). After the treatments all groups were observed for 1h. The ChAT and AChE activities were measured using spectrophotometric methods and the results compared to values obtained from saline-treated animals. In pilocarpine group was observed a significantly decreases in ChAT and AChE activities in striatum and frontal cortex of adult rats, when compared to control group. Results showed that during acute phase of seizures striatal and frontal cortex ChAT and AChE activities are diminished. Our findings suggest that seizures caused cognitive dysfunction and decreases of ChAT and AChE activities that might be related, at least in part, to the neurological problems presented by epileptic patients.

Acetylcholinesterase activities in hippocampus, frontal cortex and striatum of Wistar rats after pilocarpine-induced status epilepticus.

Experimental manipulations suggest that in vivo administration of cholinergic agonists or inhibitors of acetylcholinesterase (AChE) increases the concentration of acetylcholine. Biochemical studies have proposed a role for AChE in brain mechanisms responsible by development to status epilepticus (SE) induced by pilocarpine. The present study was aimed at investigating the changes in AChE activities in hippocampus, striatum and frontal cortex of adult rats after pilocarpine-induced SE. The control group was treated with 0.9% saline (s.c., control group) and another group received pilocarpine (400 mg/kg, s.c.). Both groups were sacrificed 1 h after treatment. The results have shown that pilocarpine administration and resulting SE produced a significant decrease in the AChE activity in the hippocampus (63%), striatum (35%) and frontal cortex (27%) of adult rats. Our results demonstrated a direct evidence of a decrease in the activity of the AChE in rat brain regions during seizure activity that could be responsible by regulation of acetylcholine levels during the establishment of SE induced by pilocarpine.

Catalase activity in cerebellum, hippocampus, frontal cortex and striatum after status epilepticus induced by pilocarpine in Wistar rats.

The mechanism underlying the vulnerability of the brain to status epilepticus (SE) induced by pilocarpine remains unknown. Oxidative stress has been implicated in a variety of acute and chronic neurologic conditions, including SE. The present study was aimed at was investigating the changes in catalase activity after pilocarpine-induced seizures and SE. The Control group was treated with 0.9% saline (NaCl, subcutaneously (s.c.)) and sacrificed 1h after the treatment. Another group was treated with pilocarpine (400 mg/kg, s.c., Pilocarpine group) and sacrificed 1h after treatment. The catalase activity in the cerebellum, hippocampus, frontal cortex and striatum of Wistar rats was determined. The results have shown that pilocarpine administration and resulting SE produced a significant increase in the catalase activity in the hippocampus (36%), striatum (31%) and frontal cortex (15%) of treated adult rats. Nevertheless, in the adult rat cerebellum after SE induced by pilocarpine no change was observed in the catalase activity. Our results demonstrated a direct evidence of an increase in the activity of the scavenging enzyme (catalase) in different cerebral structures during seizure activity that could be responsible for eliminating oxygen free radicals and might be one of the compensatory mechanisms to avoid the development of oxidative stress during the establishment of SE induced by pilocarpine. Our reports also indicate clear regional differences in the catalase activity caused by pilocarpine-induced seizures and SE and the hippocampus might be the principal area affected and cerebellum does not modify for this parameter studied during epileptic activity.

Cognitive deficits in adult rats by lead intoxication are related with regional specific inhibition of cNOS.

It is well known that lead can affect several cognitive abilities in developing animals. In this work, we investigate the effects of different sub-chronic lead doses (0, 65, 125, 250 and 500 ppm of lead acetate in their drinking water for 14 days) in the performance of male adult rats in a water maze, cue maze and inhibitory avoidance tasks. We found that the acquisition of these tasks was not affected by lead, however, the highest dosage of lead (500 ppm) impaired memory consolidation in spatial and inhibitory avoidance tasks, but not in cue maze task while the 250 ppm dose only affected retrieval of spatial memory. Additionally, hippocampal long-term potentiation (LTP) induction in the perforant path after exposing adult rats to different doses of lead was studied. LTP induction was affected in a dose-dependent manner, and treatments of 250 and 500 ppm completely blocked LTP. We investigated the effects of lead intoxication on the activity of constitutive nitric oxide synthase (cNOS) in different brain regions of adult animals. The activity of cNOS was significantly inhibited in the hippocampus and cerebellum but not in the frontal cortex and brain stem, although lead had accumulated in all brain regions. These results suggest that lead intoxication can impair memory in adult animals and this impairment might be related with region-specific effects on cNOS activity.

Effects of morphine withdrawal syndrome on endo-oligopeptidase (EC 3.4.22.19) activity.

Endo-oligopeptidase (EC 3.4.22.19), an enzyme capable of generating enkephalin by single cleavage from enkephalin-containing peptides, was examined in several areas of the central nervous system (CNS) as well as in the immune and endocrine tissues of rats chronically treated with morphine and submitted to naloxone-induced withdrawal. A specific fluorogenic substrate was used to determine the endopeptidase 22.19 activity. A non-uniform increase in endopeptidase 22.19 activity was detected in the CNS. The highest increase in endopeptidase 22.19 specific activity was found in the dorsal hippocampus (about 3.5-fold higher than control), followed by occipital and frontal cortex, substantia nigra, thalamus and hypothalamus. In peripheral tissues, a significant decrease of endopeptidase 22.19 was observed in the pineal gland, whereas the morphine withdrawal syndrome caused a slight but significant increase in lymphoid tissues such as lymph nodes and thymus. These findings are indicative of a possible participation of endopeptidase 22.19 in naloxone-induced withdrawal.

Stimulation of Na+,K+-ATPase activity in certain membranes of the rat central nervous system (CNS) by acute administration of desipramine (DMI).

1. The activities of ATPase in rat CNS were studied 3 hr after administration of the noradrenaline uptake inhibitor, desipramine (DMI: 10 mg.kg-1, i.p.). Na+K+-ATPase activity significantly increased after DMI in the whole particulate from hypothalamus and mesencephalus but no changes in frontal cortex or in pons-medulla oblongata areas were found. This increase was prevented when the animals were pretreated with the noradrenergic neurotoxic N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). 2. Purified membrane fractions from hypothalamus were obtained by differential and sucrose gradient centrifugation (0.8-1.2 M sucrose). It was observed that after DMI, Na+,K+-ATPase activity increased only in the membranous fraction lying at 0.9 M sucrose. 3. Mg2+- or Ca2+-ATPase activities were not modified by DMI treatment. 4. Citalopram, a specific serotonergic uptake inhibitor, did not affect ATPase activities. 5. The results obtained could indicate that DMI acute administration selectively stimulates Na+,K+-ATPase activity of certain membranes of the CNS after an increase in the concentration of the noradrenergic neurotransmitter in the synaptic gap.

Effect of Venezuelan equine encephalomyelitis virus infection on brain choline acetyltransferase and acetylcholinesterase activities.

Mice and rats infected with the Venezuelan equine encephalomyelitis virus showed a significant decrease in the choline acetyltransferase activity of caudate nucleus, hypothalamus, midbrain, hippocampus and frontal cortex. Acetylcholinesterase activity was not affected in any of the same brain regions analyzed. In surviving rats no alterations were observed in the activities of choline acetyltransferase, tyrosine hydroxylase, and glutamate decarboxylase 3 months after the infection.