Brain cAMP Research Articles

Brain Camp: A Summer Pipeline Program to Increase Diversity in Neurosciences.

Despite calls to increase diversity in the health care workforce, most medical fields including neurology have seen minimal advances, owing in part to the lack of developing a robust pipeline for trainees from underrepresented backgrounds. We sought to create an immersive, replicable neurology-themed summer camp and longitudinal mentorship program for underrepresented-in-medicine (URM) high-school students to encourage them to enter the training pipeline in neuroscience-related fields. We established an annual, no-cost 1-week camp for local URM students with the goals of exposing them to different health care professions within neuroscience while providing them with college application resources and long-term mentorship. A postprogram survey was distributed to assess the students' attitudes towards the camp and their desires to pursue health care careers. Over the 4 years since the founding of the camp (2016-2020), a total of 96 students participated, of whom 53% were URM, 74% came from very low-income households, and 61% had parents who did not attend college. In total, 87 students (91%) completed the postcamp survey. Nearly all (97%) of the respondents were likely to recommend the camp to their peers, and the vast majority (85%) felt that Brain Camp made them more likely to pursue careers in health care. Brain Camp seeks to address the unmet need for low barrier-to-entry programs designed for URM high-school students interested in health care careers. We envision that our camp may serve as a blueprint for other similar programs across the nation with the goal of addressing the URM pipeline in neuroscience.

Screening and evaluation of the role of immune genes of brain metastasis in lung adenocarcinoma progression based on the TCGA and GEO databases.

BackgroundBrain metastasis was one of the factors leading to the poor long-term prognosis of patients with lung adenocarcinoma (LUAD).MethodsThe expression levels of immune genes in LUAD and LUAD brain metastases tissues were analyzed in GSE161116 dataset using the GEO2R, and the levels of differential immune genes in normal lung and LUAD tissues were verified. The biological functions and signaling mechanisms of the differential immune genes were explored via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. Cox regression analysis was used to screen the prognostic factors of LUAD patients, and a risk model was constructed. The role of the model was checked in the development of LUAD via receiver operating characteristic analysis, gene set enrichment analysis, and Cox regression analysis.ResultsDifferentially expressed genes (DEGs) in brain metastasis were involved in the adaptive immune response, B cell differentiation, leukocyte migration, NF-kB signaling pathway, among others. The expression levels of TNFRSF11A, MS4A2, IL11, CAMP, MS4A1, and F2RL1 were independent factors affecting the poor prognosis of LUAD patients via Cox regression analysis and Akaike information criterion. In the constructed risk model, the overall survival of LUAD patients in the high-risk group was poor. The risk model was significantly related to the gender, clinical stage, T stage, lymph node metastasis, and survival status of LUAD patients. In addition, the risk model score was an independent risk factor that affected the poor prognosis of LUAD patients. TNFRSF11A, CAMP, F2RL1, IL11, MS4A1, and MS4A2 of the risk factors had diagnostic significance in LUAD brain metastasis and LUAD. The risk model participated in cytokinetic process, cell cycle, citrate cycle TCA cycle, etc. The risk model score was correlated with the levels of B cells memory, mast cells resting, macrophages M0, mast cells activated, neutrophils, eosinophils, T cells gamma delta, and immune cell markers.ConclusionsThe risk model based on the LUAD brain metastasis immune factors TNFRSF11A, MS4A2, IL11, CAMP, MS4A1, and F2RL1 was related to the diagnosis, poor prognosis, and immune infiltrating cells of LUAD patients, and is expected to provide a reference for the development of treatment strategies for LUAD patients.

Application of transcriptome analysis to understand the adverse effects of hydrogen peroxide exposure on brain function in common carp (Cyprinus carpio)

Hydrogen peroxide (H2O2), as a common disinfectant, has been extensively used in aquaculture. The toxicity of high ambient H2O2 for gills and liver of fish has received attention from many researchers. However, whether H2O2 exposure induced brain injury and neurotoxicity has not been reported in fish. Therefore, this study aimed to explore the potential mechanism of H2O2 toxicity in brain of common carp via transcriptome analysis and biochemical parameter detection. The fish were exposed to 0 (control) and 1 mM of H2O2 for 1 h per day lasting 14 days. The results showed that H2O2 exposure caused oxidative damage in brain evidenced by decreased glutathione (GSH), total antioxidant capacity (T-AOC) and nicotinamide adenine dinucleotide (NAD+) levels, and increased formation of malondialdehyde (MDA) and 8-hydroxy-2′-deoxyguanosine (8-OHdG). Meanwhile, H2O2 exposure reduced 5-hydroxytryptamine (5-HT) level, and down-regulated tryptophan hydroxylase 1 (tph1a), tph2, 5-hydroxytryptamine receptor 1A-beta (htr1ab) and htr2b expression in brain. Transcriptome analysis showed that H2O2 exposure up-regulated 604 genes and down-regulated 1209 genes in brain. Go enrichment displayed that the differently expressed genes (DEGs) were enriched mainly in cellular process, single-organism process, metabolic process, and biological regulation in the biological process category. Further, KEGG enrichment indicated that H2O2 exposure led to dysregulation of neurotransmitter signals including depression of glutamatergic synapse, GABAergic synapse and endocannabinoid signaling. Also, we found the alteration of three key pathways including calcium, cAMP and HIF-1 in brain after H2O2 exposure. In conclusion, our data indicated that H2O2 exposure induced oxidative damage and neurotoxicity, possibly related to dysregulation of neurotransmitters and calcium, cAMP and HIF-1 signaling pathways, which may adversely affect learning, memory and social responses of common carp. This study provided novel insight into biological effects and underlying mechanism of H2O2 toxicity in aquatic animal, and contributed to proper application of H2O2 in aquaculture.

Phosphodiesterase 4b expression plays a major role in alcohol-induced neuro-inflammation

It is increasingly evident that alcohol-induced, gut-mediated peripheral endotoxemia plays a significant role in glial cell activation and neuro-inflammation. Using a mouse model of chronic alcohol feeding, we examined the causal role of endotoxin- and cytokine-responsive Pde4 subfamily b (Pde4b) expression in alcohol-induced neuro-inflammation. Both pharmacologic and genetic approaches were used to determine the regulatory role of Pde4b.In C57Bl/6 wild type (WT) alcohol fed (WT-AF) animals, alcohol significantly induced peripheral endotoxemia and Pde4b expression in brain tissue, accompanied by a decrease in cAMP levels. Further, along with Pde4b, there was a robust activation of astrocytes and microglia accompanied by significant increases in the inflammatory cytokines (Tnfα, Il-1β, Mcp-1 and Il-17) and the generalized inflammatory marker Cox-2. At the cellular level, alcohol and inflammatory mediators, particularly LPS, Tnfα and Hmgb1 significantly activated microglial cells (Iba-1 expression) and selectively induced Pde4b expression with a minimal to no change in Pde4a and d isoforms. In comparison, the alcohol-induced decrease in brain cAMP levels was completely inhibited in WT mice treated with the Pde4 specific pharmacologic inhibitor rolipram and in Pde4b−/− mice. Moreover, all the observed markers of alcohol-induced brain inflammation were markedly attenuated. Importantly, glial cell activation induced by systemic endotoxemia (LPS administration) was also markedly decreased in Pde4b−/− mice. Taken together, these findings strongly support the notion that Pde4b plays a critical role in coordinating alcohol-induced, peripheral endotoxemia mediated neuro-inflammation and could serve as a significant therapeutic target.

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About the Poets

Role of Phosphodiesterase 4D in Memory and Cognition

Inhibition of PDE4 has been proposed as a potential treatment for series of neuropsychological conditions including memory deficits. However, most centrally acting PDE4 inhibitors have accompanying tolerability issues such as emesis and diarrhea. Therefore, it is critical to elucidate the role of each subtype of PDE4 (namely PDE4A, B and D in the brain), so that unwanted adverse effects may be avoided. Using a selective PDE4D inhibitor, BPN14770, our data suggested that PDE4D might play a critical role in mediating behaviors related to memory and cognition. BPN14770 achieves its highly selective inhibition of PDE4D through allosteric binding to the phenylalanine, which is only present in the primates, in the UCR2 region of the enzyme. As a result, the compound inhibits human and mouse PDE4D with IC50s of 8 and 130 nM, respectively. In order to elucidate the involvement of PDE4D in the memory process in intact animals, we generated a “humanized” mouse line (PEDD) by mutating the mouse UCR2 tyrosine271 to phenylalanine. In the in vitro competition binding assay with 3H labeled rolipram, BPN14770 exhibited a preferred 2‐site binding mode with the PEDD but not the wild‐type mouse brain homogenate, suggesting that the compound may be able to bind with PDE4D with different affinities in the wild‐type and PEDD mouse brains. It was then demonstrated that in both the wild‐type and PEDD mice, BPN14770 were able to improve cognition, with the minimum effective doses of 1 and 0.01 mg/kg in the novel object recognition (NOR) test, respectively. However, such dose‐response shift was not present with rolipram, a non‐selective PDE4 inhibitor. These behavioral changes were supported by elevated brain cAMP levels in the mouse brain 1 hour after treatment, which showed a similar dose‐response shift between the wild‐type and PEDD mice. Moreover, BPN‐14770 enhanced the long‐term potential in hippocampal slices obtained from both the wild‐type and PEDD mice, with the minimum effective concentration of the latter being 10‐fold smaller. Neurochemical analyses of brain lysates from PEDD mice suggested that such behavioral changes may be due to altered synaptic function, especially in the post synapses, in the prefrontal cortex and hippocampus, as indicated by increased phosphorylation of synapsin and PSD95, as well as molecular targets downstream of cAMP, such as phosphorylation of CREB and BDNF. Taken together, our data suggested that PDE4D plays an indespensable role in regulation of memory and cognition.Support or Funding InformationThis work was supported by research grants from National Institute of Mental Health to Dr. M. E Gurney (No. R44MH091791).

Molecular modifications by regulating cAMP signaling and oxidant-antioxidant defence mechanisms, produce antidepressant-like effect: A possible mechanism of etazolate aftermaths of impact accelerated traumatic brain injury in rat model

Traumatic brain injury (TBI) is one of the leading cause of psychiatric conditions in patients, amongst which, depression and anxiety are more frequent. Despite the preclinical antidepressant-like effects, clinical development of Phospodiesterase-4 (PDE4) enzyme inhibitors has been hampered due to serious side effect profiles, such as nausea and vomiting. Etazolate (ETZ) is a new generation PDE4 inhibitor with encouraging safety and tolerance profiles. In our previous studies we have addressed that ETZ produces antidepressant-like effects in animal models of depression, however, the underlying mechanism(s) following TBI have not been completely explored. Impact accelerated TBI by weight drop method causes depression-like behavioral deficits in modified open field exploration, hyper-emotionality and sucrose consumption paradigms. TBI not only causes immediate mechanical damage to the brain, but also induces biochemical changes that lead to delayed neural cell loss leading to a secondary injury. The present study examines the antidepressant effects of ETZ on the TBI-induced depression-like behavior deficits and attempts to explore the underlying mechanism. In order to understand the underlying pathology of TBI and mechanism(s) of ETZ in TBI molecular markers namely, brain cAMP, cAMP response element binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) were estimated. Additionally, the level of oxidative (lipid peroxidation) & nitrosative (nitrite) stress markers, along with antioxidant enzymes markers, such as, reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) were measured. Furthermore, the involvement of hypothalamic-pituitary adrenal (HPA) axis activity in underlying mechanism was also investigated by measuring serum corticosterone (CORT) level. The results revealed that TBI significantly altered cAMP, pCREB and BDNF levels. Moreover, a significant increase in oxidative–nitrosative stress markers levels, while, significant decreases in antioxidant enzymes markers level were observed. However, no significant change was observed in serum CORT level. Chronic ETZ (0.5 and 1 mg/kg) treatment significantly attenuated TBI-induced behavioral deficits and restored the TBI induced derangements in molecular and biochemical markers. This study indicates that ETZ modulates cAMP signaling and oxidative/antioxidant markers in the TBI model suggesting its prospect as a potential candidate for the pharmacotherapy of depression.

EVALUATION OF CYCLIC ADENOSINE MONOPHOSPHATE AND NEUROTRANSMITTERS IN EXPERIMENTAL OBESITY: IMPACT OF BLACK PEPPER AND COFFEE AQUEOUS EXTRACTS

ABSTRACTObjective: This study aims to evaluate the effect of black pepper and coffee extracts on chronic and acute experimental-induced obesity and energyhomeostasis.Methods: Rats were divided into 10 groups including control, high-fat diet (HFD), triton, HFD+triton, black pepper+HFD, black pepper+HFD+triton,coffee+HFD, coffee+HFD+triton, mixture+HFD, and mixture+HFD+triton groups. Blood glucose, serum insulin, and insulin resistance were estimated.Body mass index, food efficiency intake, and body weight gain were calculated. Lipid profile, liver and kidney functions were measured, serum and braincyclic adenosine monophosphate (cAMP) was estimated, and brain neurotransmitters were measured by high-performance liquid chromatography.Furthermore, histopathology of liver was performed.Results: Findings showed that blood glucose, insulin resistance, lipid profile, kidney and liver functions as well as brain cAMP and neurotransmitterswere significantly increased, concomitant with a significant decrease in insulin resistance and serum cAMP in both HFD and triton-induced obesitygroups compared to control.Conclusion: Supplementation with black pepper extract, coffee extract, and a mixture of both significantly improved these findings. In conclusion,black pepper and coffee extracts are overlooked as promising weight reduction and antihyperlipidemic agents.Keywords: Energy homeostasis, Obesity, Black pepper extract, Coffee extract, Cyclic adenosine monophosphate, Neurotransmitters.

Enhancing brain cAMP trough PDE-7 inhibitors: A new Alzheimer’s disease pharmacotherapy approach

Enhancing brain cAMP trough PDE-7 inhibitors: A new Alzheimer’s disease pharmacotherapy approach

The effect of phosphodiesterase inhibitors on the extinction of cocaine-induced conditioned place preference in mice

Several phosphodiesterase inhibitors (PDEis) improve cognition, suggesting that an increase in brain cAMP and cGMP facilitates learning and memory. Since extinction of drug-seeking behavior requires associative learning, consolidation and formation of new memory, the present study investigated the efficacy of three different PDEis in the extinction of cocaine-induced conditioned place preference (CPP) in B6129S mice. Mice were conditioned by escalating doses of cocaine which was resistant to extinction by free exploration. Immediately following each extinction session mice received (a) saline/vehicle, (b) rolipram (PDE4 inhibitor), (c) BAY-73-6691 (PDE9 inhibitor) or (d) papaverine (PDE10A inhibitor). Mice that received saline/vehicle during extinction training showed no reduction in CPP for >10 days. BAY-73-6691 (a) dose-dependently increased cGMP in hippocampus and amygdala, (b) significantly facilitated extinction and (c) diminished the reinstatement of cocaine CPP. Rolipram, which selectively increased brain cAMP levels, and papaverine which caused increases in both cAMP and cGMP levels, had no significant effect on the extinction of cocaine CPP. The results suggest that increase in hippocampal and amygdalar cGMP levels via blockade of PDE9 has a prominent role in the consolidation of extinction learning.

Neurotropic effects of the optical isomers of the selective adenosine cyclic 3',5'-monophosphate phosphodiesterase inhibitor rolipram in rats in-vivo.

The efficacy of the selective adenosine cyclic 3',5'-monophosphate (cAMP) phosphodiesterase (PDE) inhibitor (+/-)-rolipram and its optical isomers (0.006 to 25 mg kg-1) in inducing characteristic behavioural changes like hypothermia, hypoactivity, forepaw shaking, grooming and head twitches in rats has been examined. (+)-Rolipram was found some 15 times less potent than the racemate suggesting a stereoselective interaction with a rat brain cAMP phosphodiesterase isoenzyme. Following their intracerebral administration, the stereoisomers also demonstrated their unusual potency ratio. These findings suggested that (+)-rolipram is a less potent neurotropic PDE inhibitor in-vivo than its (-)-enantiomer.

Specific inhibition of adenylyl-cyclase isoform 5 by mood stabilizers may be related to their mechanism of action

Lithium, valproate and carbamazepine decrease brain cAMP. Adenylyl-cyclase (AC), which synthesizes cAMP has nine membrane-bound isoforms (AC1-AC9). In this study we used COS7 cells transfected with cDNA of each of the isoforms to study the effect of a therapeutic concentration of each of lithium, carbamazepine and valproate on ACs activity. AC5 was the most inhibitable isoform by lithium and carbamazepine either when stimulated by forskolin or by a D1 agonist. Ten mM Mg2+ reduced lithium-induced AC5 inhibition by 70% and in silico analysis suggested that carbamazepine preferentially affects AC1 and AC5 by interacting with two amino-acids at the catechol-estrogen binding site region. Valproate did not inhibit any AC isoform suggesting it decreases cAMP levels via a different mechanism. AC5 knockout mice behaved in the forced-swim-test similarly to antidepressant- or lithium-treated wildtypes implying that AC5 inhibition may be involved in the antidepressant effect of lithium and carbamazepine. Specific AC5 inhibitors may be mood-stabilizers or antidepressants.

Effect of lipid peroxidation conditions on calcium-dependent activity of phosphodiesterase 3′,5′-cAMP in the rat brain

3′,5′-cAMP plays an important role as a second messenger molecule controlling multiple cellular processes in the brain. Its levels are decreased by phosphodiesterases (PDEs), responsible for hydrolysis of intracellular cAMP. A part of the PDE activity is dependent on the effect of calcium, mediated by its binding to calmodulin. During oxidative stress, precisely these changes in calcium concentration are responsible for cell damage. We have examined the effects of oxidative stress conditions on the activity of PDE in rat brain homogenates. We found a different influence of activated lipid peroxidation conditions (Fe2+ with ascorbate and increased temperature) on the calcium-dependent and calcium-independent PDE activity. The inhibition of Ca2+-dependent PDE was observed, while Ca2+-independent PDE was not influenced. We assume that it might be the impact of lipid peroxidation products or any mechanism activated by the higher temperature on the interaction of the Ca2+-dependent isoform of PDE with the complex calcium-calmodulin. Another explanation might be that the formation of the functioning calcium-calmodulin complex is impossible in these conditions.

Tadalafil, a long-acting type 5 phosphodiesterase isoenzyme inhibitor, improves neurological functional recovery in a rat model of embolic stroke

Sildenafil, a type 5 phosphodiesterase isoenzyme (PDE5) inhibitor with a short half-life, increases brain cyclic guanosine monophosphate (cGMP) levels and improves neurological functional recovery when administered after stroke. In the present study, we investigated the effects of tadalafil (Cialis), a long acting PDE5 inhibitor, on brain cGMP levels, neurogenesis, angiogenesis, and neurological function during stroke recovery in a rat model of embolic stroke. Male Wistar rats ( n = 28) were subjected to embolic middle cerebral artery (MCA) occlusion. Tadalafil was orally administered every 48 h at a dose of 2 mg/kg or 10 mg/kg for 6 consecutive days starting 24 h after stroke onset. Control animals received the equivalent volume of saline at the same time points. For mitotic labeling, bromodeoxyuridine (BrdU, 100 mg/kg) was administered twice a day at 5, 6, and 7 days after stroke. ELISA assays were performed to evaluate the specificity of the effect of tadalafil on cGMP. Treatment with tadalafil at a dose of 2 or 10 mg/kg significantly improved neurological functional recovery compared with saline-treated rats. In addition, tadalafil treatment increased cerebral vascular density and the percentage of BrdU-positive endothelial cells around the ischemic boundary compared with saline-treated rats. Moreover, tadalafil-treated rats showed greater ipsilateral SVZ cell proliferation than saline-treated rats. However, treatment with tadalafil did not reduce infarct volume when compared to the saline group. Tadalafil selectively increased cGMP but not cyclic adenosine monophosphate (cAMP) in brain. Our data demonstrate that treatment of ischemic stroke with tadalafil improved functional recovery, which was associated with increases of brain cGMP levels and enhancement of angiogenesis and neurogenesis.

Chloride Conductance Is Required for the Protein Kinase A and Rac1-dependent Phosphorylation of Moesin at Thr-558 by KCl in PC12 Cells

Moesin is a member of the ERM family, a family of cross-linkers between the plasma membrane and the actin cytoskeleton, which are known to be activated by phosphorylation. Previously, we reported the RhoA and Rho kinase-dependent phosphorylation of moesin at Thr-558 in hippocampal neuronal cells by glutamate. Here we studied the induction of moesin phosphorylation by KCl (60 mm) in PC12 cells. Moesin phosphorylation at Thr-558 was increased after 2 min of KCl treatment, peaked at 5 min, and returned to the basal level by 60 min. KCl also activated Rac1, but not RhoA, in PC12 cells, and KCl-induced moesin phosphorylation was suppressed in dominant negative Rac1 (N17 Rac1)-expressed cells. The inhibition of protein kinase A (PKA), known as an upstream kinase of Rac1, abolished Rac1 activation and moesin phosphorylation by KCl. Interestingly, the phosphorylation of moesin by KCl was independent of KCl-induced membrane depolarization and calcium influx but was dependent on KCl-induced chloride conductance. 60 mm KCl induced chloride conductance in PC12 cells, and pretreatment with Cl- channel blocker abolished Rac1 activation and moesin phosphorylation by KCl. These results suggest that the phosphorylation of moesin at Thr-558 in PC12 cells by KCl treatment is PKA- and Rac1-dependent and that KCl-induced chloride conductance is involved in the activation of this signaling system.

Propionic and methylmalonic acids increase cAMP levels in slices of cerebral cortex of young rats via adrenergic and glutamatergic mechanisms

We have previously described that propionic (PA) and methylmalonic (MMA) acids increased the in vitro phosphorylation of cytoskeletal proteins through cAMP-dependent protein kinase and glutamate. In the present study we investigated the in vitro effects of 1 mM glutamate, 2.5 mM MMA and 2.5 mM PA on cAMP levels in the slices of cerebral cortex of young rats. Results showed that PA, MMA and glutamate increased cAMP levels after 30 min of incubation, while the beta-adrenergic agonist epinephrine elicited a similar effect only at a shorter incubation time. Then effects were prevented by the beta-adrenergic antagonist propranolol, rather than by glutamate antagonists (AP5, CNQX and MCPG), suggesting that they were mediated by beta-adrenergic receptors. In addition, glutamate antagonists per se induced increased cAMP levels; however propranolol prevented only the effect elicited by the metabotropic glutamate antagonist MCPG. Taken together, it is feasible that PA and MMA increase cAMP synthesis via a beta-adrenergic/G protein coupled pathway, in a glutamate-dependent manner. Although additional studies will be necessary to evaluate the importance of these observations for the neuropathology of propionic and methylmalonic acidemias, it is possible that high brain cAMP levels may contribute to a certain extent to the neurological dysfunction of the affected individuals.

?-adrenergic receptor density and adenylate cyclase activity in lead-exposed rat brain after cessation of lead exposure

To understanding the reversible or irreversible harm to the beta-adrenergic system in the brain of lead-exposed rats, this study sets up an animal model to estimate the change in the sympathetic nervous system of brain after lead exposure was withdrawn. We address the following topics in this study: (a) the relationship between withdrawal time of lead exposure and brain beta-adrenergic receptor, blood lead level, and brain lead level in lead-exposed rats after lead exposure was stopped; and (b) the relationship between lead level and beta-adrenergic receptor and cyclic AMP (c-AMP) in brain. Wistar rats were chronically fed with 2% lead acetate and water for 2 months. Radioligand binding was assayed by a method that fulfilled strict criteria of beta-adrenergic receptor using the ligand [125I]iodocyanopindolol. The levels of lead were determined by electrothermal atomic absorption spectrometry. The c-AMP level was determined by radioimmunoassay. The results showed a close relationship between decreasing lead levels and increasing numbers of brain beta-adrenergic receptors and brain adenylate cyclase activity after lead exposure was withdrawn. The effect of lead exposure on the beta-adrenergic system of the brain is a partly reversible condition.

Chronic prenatal exposure to cocaine alters cerebrovascular responses in newborn pigs.

Maternal cocaine abuse may increase the incidence of perinatal asphyxia. In nonexposed asphyxiated neonates, decreased cerebrospinal fluid (CSF) cAMP concentrations are associated with poor neurological outcome. On the other hand, cocaine increases central nervous system (CNS) cAMP. Therefore, we hypothesized that in utero cocaine exposure may increase brain cAMP and thereby preserve cerebrovascular responses to cAMP-dependent stimuli following asphyxia. Pregnant pigs received either cocaine (1 mg/kg, i.v.) twice weekly during the last trimester or normal saline vehicle (sham-control) and were allowed to deliver vaginally at term. Cranial windows were implanted in the newborn pigs within the first week of life and used to collect CSF for cAMP determinations and to assess changes in pial arteriolar diameters (PAD). In the first part of the study, pial arteriolar responses to different vasodilator and vasoconstrictor stimuli were evaluated in piglets prior to asphyxia (n = 20). In newborn pigs exposed to cocaine, cerebrovascular responses to hypercapnia and norepinephrine were significantly exaggerated compared to controls. Then, piglets were randomly selected for the second part of the study that involved prolonged asphyxia (n = 12). In cocaine-exposed but not sham-control piglets, CSF cAMP increased markedly during asphyxia. In the sham piglets, but not the cocaine-exposed piglets, CSF cAMP fell progressively below the baseline during recovery. Cerebrovascular reactivity to cAMP-dependent stimuli (hypercapnia and isoproterenol) was preserved during recovery from asphyxia in the cocaine-exposed piglets but significantly attenuated in the sham controls. We conclude that piglets with chronic prenatal exposure to cocaine show exaggerated cerebrovascular responses to vasogenic stimuli and preserved cAMP-dependent cerebral vasoreactivity following asphyxia.

Effects of rolipram, a phosphodiesterase 4 inhibitor, in combination with imipramine on depressive behavior, CRE-binding activity and BDNF level in learned helplessness rats

The brain cAMP regulating system and its downstream elements play a pivotal role in the therapeutic effects of antidepressants. We previously reported the increase in activities of phosphodiesterase 4, a major phosphodiesterase isozyme hydrolyzing cAMP, in the frontal cortex and hippocampus of learned helplessness rats, an animal model for depression. The present study was undertaken to examine the combination of effects of rolipram, a phosphodiesterase 4 inhibitor, with imipramine, a typical tricyclic antidepressant, on depressive behavior in learned helplessness rats. Concurrently, cAMP-response element (CRE)-binding activity and brain-derived neurotrophic factor (BDNF) levels related to the therapeutic effects of antidepressants were determined. Repeated administration of imipramine (1.25–10 mg/kg, i.p.) or rolipram (1.25 mg/kg, i.p.) reduced the number of escape failures in learned helplessness rats. Imipramine could not completely ameliorate the escape behavior to a level similar to that of non-stressed rats even at 10 mg/kg. However, repeated coadministration of rolipram with imipramine (1.25 and 2.5 mg/kg, respectively) almost completely eliminated the escape failures in learned helplessness rats. The reduction of CRE-binding activities and BDNF levels in the frontal cortex or hippocampus in learned helplessness rats were ameliorated by treatment with imipramine or rolipram alone. CRE-binding activities and/or BDNF levels of the frontal cortex and hippocampus were significantly increased by treatment with a combination of rolipram and imipramine compared to those in imipramine-treated rats. These results indicated that coadministration of phosphodiesterase type 4 inhibitors with antidepressants may be more effective for depression therapy and suggest that elevation of the cAMP signal transduction pathway is involved in the antidepressive effects.

Decreased expression of brain cAMP response element-binding protein gene following pentylenetetrazol seizure

The present study investigated whether the expression of the cAMP response element-binding protein (CREB) in the rat brain is altered following an acute self-limited seizure induced by pentylenetetrazol (PTZ). Male rats were injected intraperitoneally with a single convulsive dose (45 mg/kg) of PTZ, and the matched controls were given saline. For immunohistochemistry, animals were perfused with 4% parafomaldehyde at 24 h following PTZ seizures, and CREB immunoreactivity was examined in rat brain. For real-time RT-PCR, animals were sacrificed at 2 and 24 h and 1 week following PTZ seizures. Tissues from different rat brain regions were micropunched and subjected to real-time RT-PCR using Taqman probe. The CREB immunoreactive profiles were significantly decreased in CA3 and dentate gyrus of hippocampal formation, sensory cerebral cortex and thalamus at 24 h after PTZ seizures. Consistent with changes in CREB immunoreactivity, levels of CREB mRNA were significantly decreased in the hippocampus, cerebral cortex, amygdala and thalamus at 24 h after PTZ seizures. No significant change was found for CREB mRNA expression in these regions at 2 h or 1 week following PTZ seizures. These results show that a brief seizure caused a decline in CREB expression up to 24 h later.