Biomedical subjects

Marisela Morales

Publications and source records attributed to Marisela Morales.

At least 19 recordsLinked to original sources

PubMed2006

Antipsychotic clozapine inhibits the function of alpha7-nicotinic acetylcholine receptors.

The effects of the antipsychotic clozapine on the function of the cloned alpha(7) subunit of the nicotinic acetylcholine (nACh) receptor expressed in Xenopus oocytes was investigated by using the two-electrode voltage-clamp technique. Clozapine reversibly inhibited nicotine (10 microM)-induced currents in a concentration-dependent manner (300 nM to 90 microM), with an IC(50) value of 3.2+/-0.4 microM. The effect of clozapine was not dependent on the membrane potential. Clozapine did not affect the activity of endogenous Ca(2+)-dependent Cl(-) channels since the inhibition by clozapine was unaltered by the intracellularly injected Ca(2+) chelator BAPTA and perfusion with Ca(2+)-free bathing solution containing 2mM Ba(2+). Clozapine decreased the maximal nicotine-induced responses without significantly affecting its potency, indicating that it acts as a noncompetitive antagonist on alpha(7)-nACh receptors. In hippocampal slices, the whole-cell recordings from CA1 pyramidal neurons indicated that the increases in the frequency and amplitudes of the GABA-mediated spontaneous inhibitory postsynaptic currents induced by bath application of 2 mM choline, a specific agonist for alpha(7)-nACh receptors, were abolished after 10 min application of 5 microM clozapine. In conclusion, these results demonstrate that clozapine inhibits the function of alpha(7)-nACh receptors expressed in Xenopus oocytes and in hippocampal neurons.

Animals↗

PubMed2006

Expression of serotonergic receptors in psoriatic skin.

Psoriasis appears to be influenced by stress, which causes release of adrenal hormones. Serotonin, or hormonal actions on serotonin and serotonin receptors, may have a role in psoriasis. Distribution of serotonin receptors was studied in involved and noninvolved skin in patients with psoriasis and compared to normal skin, by using immunohistochemistry and antibodies to 5-HT1A, 5-HT2A and 5-HT3 receptors (R). There was a decreased (P<0.001) number of 5-HT1AR positive cells, the majority being tryptase positive, in involved and noninvolved psoriatic papillary dermis, compared to normal skin. 5-HTlAR expression was also found in the upper part of the epidermis, on vessel walls and on melanocytes. 5-HT2AR expressing papillary mononuclear cells, CD3 positive, were increased (P<0.001 and P<0.01, respectively) in involved and noninvolved psoriatic skin, compared to normal skin, an increase (P<0.01) also being found in the involved compared to noninvolved skin. Expression of 5-HT3R could be found in the basal epidermal layer of noninvolved but not in the involved skin of psoriasis, where it was only found in the acrosyringium. The present findings are compatible with the 5-HT1A and 5-HT2A receptors having antagonistic functions, and raise the possibility of using receptor specific drugs in the treatment of psoriasis.

Adult↗

PubMed2006

Effect of methamphetamine self-administration on tyrosine hydroxylase and dopamine transporter levels in mesolimbic and nigrostriatal dopamine pathways of the rat.

RATIONALE AND OBJECTIVES: Many studies have examined the effect of experimenter-delivered methamphetamine on the mesolimbic and nigrostriatal dopamine pathways. In contrast, little is known about the effect of methamphetamine self-administration on these neuronal pathways. We studied the effect of methamphetamine self-administration on two key regulators of dopamine transmission, tyrosine hydroxylase (TH), and dopamine transporter (DAT), in components of the mesolimbic and nigrostriatal dopamine pathways. METHODS: Rats self-administered methamphetamine (0.1 mg/kg per infusion, fixed-ratio-1 reinforcement schedule) or saline (control condition) for 9 h/day over 10 days. The brains of these rats were collected after 1 or 30 days of forced abstinence and the expression levels of TH and DAT were assayed by in situ, hybridization and western blot. RESULTS: TH mRNA and protein levels were increased in the ventral tegmental area (VTA, the cell body region of the mesolimbic dopamine system) and the substantia nigra pars compacta (SNC, the cell body region of the nigrostriatal dopamine system) after 1 day, but not 30 days, of forced abstinence from methamphetamine. In contrast, methamphetamine self-administration had no effect on TH protein levels in dopaminergic terminals located in the nucleus accumbens and caudate-putamen. In addition, methamphetamine self-administration had no effect on DAT mRNA levels in the VTA. CONCLUSIONS: Results suggest that extended daily access to self-administered methamphetamine results in a transient, short-lasting effect on mesolimbic and nigrostriatal dopamine neurons of the rat brain.

Animals↗

PubMed2006

Stimulation of adenosine receptors selectively activates gene expression in striatal enkephalinergic neurons.

In the striatum, adenosine A2A and dopamine D2 receptors exert reciprocal antagonistic interactions that modulate the function of GABAergic enkephalinergic neurons. We have previously shown that stimulation of adenosine A1 receptors allows the stimulation of A2A receptors to overcome a tonic inhibitory effect of D2 receptors and induce striatal expression of c-fos. In the present work, by studying co-localization of c-Fos immunoreactivity and preproenkephalin and preprodynorphin transcripts, we show that co-administration of the A1 receptor agonist CPA and the A2A receptor agonist CGS 21680 increases the striatal expression of c-fos in GABAergic enkephalinergic but not in GABAergic dynorphinergic neurons. Co-administration of CPA and CGS 21680 also induced a significant increase in the striatal expression of preproenkephalin. The results underscore the role of adenosine in the activation of gene expression in the GABAergic enkephalinergic neuron.

Adenosine↗

PubMed2006

NrCAM in addiction vulnerability: positional cloning, drug-regulation, haplotype-specific expression, and altered drug reward in knockout mice.

Several lines of evidence support roles for the cell adhesion molecule NrCAM in addictions. Fine mapping within a chromosome 7 region that contains previously linked and associated genomic markers identifies NrCAM haplotypes that are associated with substance abuse vulnerabilities in four samples of abusers and controls. Differential display identifies NrCAM as a drug regulated gene. NrCAM is expressed in neurons linked to reward and memory. NrCAM displays haplotype-specific gene expression in human post-mortem brain samples. Knockout mice display reduced opiate- and stimulant-conditioned place preferences. These observations support NrCAM as a positionally cloned and drug-regulated gene whose variants are likely to change expression and alter substance abuse vulnerabilities in human addictions and animal models of drug reward.

Amphetamine-Related Disorders↗

PubMed2005

Neuroregenerative effects of BMP7 after stroke in rats.

Previous reports have indicated that the expression of bone morphogenetic protein-7 (BMP7) is enhanced after ischemic injury in brain. This upregulation may induce endogenous neurorepair in the ischemic brain. The purpose of this study was to examine neuroregenerative effects of BMP7 after ischemia-reperfusion injury. Adult Sprague-Dawley rats were anesthetized with chloral hydrate. Right middle cerebral artery (MCA) was transiently ligated with 10-O suture for 1 h. One day after MCA occlusion, vehicle or BMP7 was infused to the contralateral cerebral ventricle. To identify possible neurogenesis, bromodeoxyurindine (BrdU) was systemically injected on the fourth and fifth days after MCA occlusion. Animals treated with BMP7 showed a rapid correction of body asymmetry and neurological deficits, suggesting BMP7 facilitates recovery after stroke. Animals were sacrificed at 1 month after stroke and brains were analyzed using immunohistological techniques. BMP7 treatment enhanced immunoreactivity of BrdU in the subventricular zone, lesioned cortex, and corpus callosum. These BrdU-positive cells co-labeled with nestin and NeuN. Our behavioral and anatomical data suggest that BMP7 promotes neuroregeneration in stroke animals, possibly through the proliferation of new neuronal precursors after ischemia.

Analysis of Variance↗

PubMed2005

Gene expression evidence for remodeling of lateral hypothalamic circuitry in cocaine addiction.

By using high-density oligonucleotide arrays, we profiled gene expression in reward-related brain regions of rats that developed escalated cocaine intake after extended access to cocaine (6 h per day). Rats allowed restricted daily access to cocaine (only 1 h) that displayed a stable level of cocaine intake and cocaine naive rats were used for controls. Four analysis methods were compared: Affymetrix microarray suite 4 and microarray suite 5, which use perfect-match-minus-mismatch models, and dchip and rma, which use perfect-match-only models to generate expression values. Results were validated by RT-PCR in individual animals from an independent replication of the experiment. A small number of genes was associated with escalated cocaine intake (ESC genes). Unexpectedly, of the brain regions examined [prefrontal cortex, nucleus accumbens, septum, lateral hypothalamus (LH), amygdala, and ventral tegmental area], the LH was the most transcriptionally responsive in escalation of cocaine intake. Most of the ESC genes identified are also expressed during synaptogenesis and synaptic plasticity and include genes that code for several presynaptic and postsynaptic proteins involved in neurotransmission. These results suggest that LH intrinsic circuitry undergoes a structural reorganization during escalation of cocaine use. This remodeling of LH circuitry could contribute to the chronic deficit in reward function that has been hypothesized to drive the transition to drug addiction. Results also support the value of using multiple analysis strategies to identify the most robust changes in gene expression and to compensate for the biases that affect each strategy.

Animals↗

PubMed2005

(+/-)-3,4-Methylenedioxymethamphetamine administration to rats does not decrease levels of the serotonin transporter protein or alter its distribution between endosomes and the plasma membrane.

We showed that the serotonin (5-HT) neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) reduces brain tissue 5-HT, decreases expression of 5-HT transporter (SERT) protein, and increases expression of glial fibrillary acidic protein (GFAP). In contrast, doses of (+/-)-3,4-methylenedioxymethamphetamine (MDMA) that decrease brain tissue 5-HT fail to alter expression of SERT or GFAP. Using a new and highly sensitive anti-SERT antibody, we determined whether MDMA alters the subcellular distribution of SERT protein by measuring SERT expression in endosomes and plasma membranes 2 weeks after MDMA administration. Rat brain tissues (caudate, cortex, and hippocampus) were collected 3 days and 2 weeks after MDMA (7.5 mg/kg i.p., every 2 h x 3 doses) or 5,7-DHT (150 microg/rat i.c.v.) administration. Representative results from cortex are as follows. At both 3 days and 2 weeks postinjection, MDMA decreased tissue 5-HT (65%) and had no effect on GFAP expression. MDMA increased heat shock protein 32 (HSP32; a marker for microglial activation) expression (30%) at 3 days, but not 2 weeks. MDMA did not alter SERT expression at either time point and did not alter SERT levels in either endosomes or plasma membranes (2 weeks). 5,7-DHT decreased tissue 5-HT (80%), increased HSP32 expression at both time points (about 50%), and increased GFAP expression at 2 weeks (40%). 5,7-DHT decreased SERT expression (33%) at 2 weeks, but not at 3 days. These findings indicate that a dosing regimen of MDMA that depletes brain 5-HT does not alter SERT protein expression or the distribution of SERT between endosomes and the plasma membrane and does not produce detectable evidence for neurotoxicity.

5,7-Dihydroxytryptamine↗

PubMed2005

Additive effects of endogenous cannabinoid anandamide and ethanol on alpha7-nicotinic acetylcholine receptor-mediated responses in Xenopus Oocytes.

The interaction between the effects of the endogenous cannabinoid receptor agonist anandamide and ethanol on the function of homomeric alpha(7)-nicotinic acetylcholine (nACh) receptors expressed in Xenopus oocytes were investigated using the two-electrode voltage-clamp technique. Anandamide and ethanol reversibly inhibited currents evoked with 100 microM acetylcholine in a concentration-dependent manner. Coapplication of anandamide and ethanol caused a significantly greater inhibition of alpha(7)-nACh receptor function than anandamide or ethanol alone. The IC(50) value of 238 +/- 34 nM for anandamide inhibition decreased significantly to 104 +/- 23 nM in the presence of 30 mM ethanol. The inhibition of alpha(7)-mediated currents by coapplication of anandamide and ethanol was not altered by phenylmethylsulfonyl fluoride, an inhibitor of anandamide hydrolyzing enzyme, or N-(4-hydroxyphenyl)-arachidonylamide, an anandamide transport inhibitor. Analysis of oocytes by matrix-assisted laser desorption/ionization technique indicated that ethanol treatment did not alter the lipid profile of oocytes, and there is negligible, if any, anandamide present in these cells. Results of studies with chimeric alpha(7)-nACh-5-HT(3) receptors comprised of the amino-terminal domain of the alpha(7)-nACh receptor and the transmembrane and carboxyl-terminal domains of 5-HT(3) receptors suggest that although ethanol inhibition of the alpha(7)-nACh receptor is likely to involve the N-terminal region of the receptor, the site of action for anandamide is located in the transmembrane and carboxyl-terminal domains of the receptors. These data indicate that endocannabinoids and ethanol potentiate each other's inhibitory effects on alpha(7)-nACh receptor function through distinct regions of the receptor.

Acetylcholine↗

PubMed2005

Role of adenosine in the control of homosynaptic plasticity in striatal excitatory synapses.

Long-lasting, activity-dependent changes in synaptic efficacy at excitatory synapses are critical for experience-dependent synaptic plasticity. Synaptic plasticity at excitatory synapses is determined both presynaptically by changes in the probability of neurotransmitter release, and postsynaptically by changes in the availability of functional postsynaptic glutamate receptors. Two kinds of synaptic plasticity have been described. In homosynaptic or Hebbian plasticity, the events responsible for synaptic strengthening occur at the same synapse as is being strengthened. Homosynaptic plasticity is activity-dependent and associative, because it associates the firing of a postsynaptic neuron with that of the presynaptic neuron. Heterosynaptic plasticity, on the other hand, is activity-independent and the synaptic strength is modified as a result of the firing of a third, modulatory neuron. It has been suggested that long-term changes in synaptic strength, which are associated with gene transcription, can only be induced with the involvement of heterosynaptic plasticity. The neuromodulator adenosine plays an elaborated pre- and postsynaptic control of glutamatergic neurotransmission. This paper reviews the evidence suggesting that in some striatal excitatory synapses, adenosine can provide the heterosynaptic-like modulation essential for stabilizing homosynaptic plasticity without the need of a "third, modulatory neuron".

Adenosine↗

PubMed2004

Differential effects of endogenous and synthetic cannabinoids on alpha7-nicotinic acetylcholine receptor-mediated responses in Xenopus Oocytes.

The effects of endogenous and synthetic cannabinoid receptor agonists, including 2-arachidonoylglycerol (2-AG), R-methanandamide, WIN55,212-2 [4,5-dihydro-2-methyl-4(4-morpholinylmethyl)-1-(1-naphthalenylcarbonyl)-6H-pyrrolo[3,2,1ij]quinolin-6-one], and CP 55,940 [1alpha,2beta-(R)-5alpha]-(-)-5-(1,1-dimethyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl-phenol], and the psychoactive constituent of marijuana, Delta9-tetrahydrocannabinol (Delta9-THC), on the function of homomeric alpha7-nicotinic acetylcholine (nACh) receptors expressed in Xenopus oocytes was investigated using the two-electrode voltage-clamp technique. The endogenous cannabinoid receptor ligands 2-AG and the metabolically stable analog of anandamide (arachidonylethanolamide), R-methanandamide, reversibly inhibited currents evoked with ACh (100 microM) in a concentration-dependent manner (IC50 values of 168 and 183 nM, respectively). In contrast, the synthetic cannabinoid receptor agonists CP 55,940, WIN55,212-2, and the phytochemical Delta9-THC did not alter alpha7-nACh receptor function. The inhibition of alpha7-mediated currents by 2-AG was found to be non-competitive and voltage-independent. Additional experiments using endocannabinoid metabolites suggested that arachidonic acid, but not ethanolamine or glycerol, could also inhibit the alpha7-nACh receptor function. Whereas the effects of arachidonic acid were also noncompetitive and voltage-independent, its potency was much lower than 2-AG and anandamide. Results of studies with chimeric alpha7-nACh-5-hydroxytryptamine (5-HT)3 receptors comprised of the amino-terminal domain of the alpha7-nACh receptor and the transmembrane and carboxyl-terminal domains of 5-HT3 receptors indicated that the site of interaction of the endocannabinoids with the alpha7-nAChR was not located on the N-terminal region of the receptor. These data indicate that cannabinoid receptor ligands that are produced in situ potently inhibit alpha7-nACh receptor function, whereas the synthetic cannabinoid ligands, and Delta9-THC, are without effect, or are relatively ineffective at inhibiting these receptors.

Analgesics, Non-Narcotic↗

PubMed2004

Cannabinoid CB1 receptor and serotonin 3 receptor subunit A (5-HT3A) are co-expressed in GABA neurons in the rat telencephalon.

Among all described serotonin (5-HT) receptors in mammals, the type three (5-HT3) is the only ligand-gated ion channel receptor for serotonin. By using double in situ hybridization histochemistry, we found co-expression of the functional 5-HT3A subunit of the 5-HT3 receptor and the central CB1 cannabinoid receptor in neurons of the rat telencephalon. Double-labeled 5-HT3A/CB1 neurons were found in the anterior olfactory nucleus, superficial and deep layers of the cortex, hippocampal formation (hippocampus, dentate gyrus, subiculum, and entorhinal cortex) and amygdala. Analysis of the proportion of neurons co-expressing 5-HT3A and CB1 receptors in the cortex and amygdala showed that, depending on the brain region, 37-53% of all neurons expressing the 5-HT3A subunit also expressed CB1 transcripts; 16-72% of the total population of neurons expressing CB1 mRNA co-expressed the 5-HT3A subunit. By using a combination of double in situ hybridization and immunohistochemistry, we demonstrated that 5-HT3A/CB1-expressing neurons contained the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). These results imply that in distinct regions of the telencephalon, GABA neurons that react to cannabinoids may also be responsive to serotonin through 5-HT3 receptors. Cellular coexistence of 5-HT3A and CB1 transcripts in interneurons of the cortex, hippocampal formation, and amygdala suggest possible interactions between the cannabinoid and serotonergic systems at the level of GABA neurotransmission in brain areas involved in cognition, memory, and emotion.

Animals↗

PubMed2003

Direct activation by dopamine of recombinant human 5-HT1A receptors: comparison with human 5-HT2C and 5-HT3 receptors.

The effects of dopamine (DA) on the function of human 5-HT1A receptors expressed in Xenopus oocytes and CHO-K1 cells were investigated. In addition, the effect of DA on the activation of three different types of human 5-HT receptors (5-HT1A, 5-HT2C, and 5-HT3) were studied comparatively in Xenopus oocyte expression system. Application of 5-HT or DA in oocytes coexpressing 5-HT1A receptors and G-protein-activated inwardly rectifying potassium channels (GIRK1) induced inward currents with respective EC50 values of 4.2 nM and 11.2 microM. Maximal responses induced by DA were 85 +/- 4% of maximal 5-HT currents and DA responses were blocked by the specific 5-HT1A antagonist, WAY-100635 (50 nM). In CHO-K1 cells expressing 5-HT1A receptors, 5-HT and DA inhibited the specific binding of selective antagonist [3H]-8-OH-DPAT with IC50 values of 10.2 nM and 1.4 microM, and both 5-HT and DA inhibited the forskolin-induced accumulation of cAMP. In oocytes expressing 5-HT2C receptors, 5-HT and DA induced inward currents with respective EC50 values of 6.2 nM and 67.7 microM. Magnitudes of maximal DA induced currents were 42 +/- 3% of maximal 5-HT responses and blocked by the 5-HT2 antagonist, piperazine (1 microM). In oocytes expressing 5-HT3 receptors, 5-HT and DA induced fast inward currents with respective EC50 values of 2.1 microM and 266.3 microM. Maximal DA induced currents were 37 +/- 3% of maximal 5-HT responses and blocked the specific 5-HT3 antagonist LY-278584 (0.1 microM). Comparison of the potencies and efficacies of 5-HT and DA indicated that the relative potency of DA increased in the order of 5-HT3 > 5-HT1A > 5-HT2C, and relative efficacy increased in the order of 5-HT1A > 5-HT2C > 5-HT3. These results suggest that although DA activates different subtypes of human 5-HT receptors directly, the potency and efficacy of the binding site varies significantly among different receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2003

Selective induction of c-Fos immunoreactivity in the prelimbic cortex during reinstatement of heroin seeking induced by acute food deprivation in rats.

We previously reported that acute 1-day food deprivation reinstates heroin seeking in rats. The goal of the present study was to begin identifying brain sites potentially involved in this effect. For this purpose, we measured, by immunohistochemistry, the expression of c-Fos following a test for food deprivation-induced reinstatement. Groups of rats (n=9-10 per group) were trained to lever-press for heroin (0.05-0.1mg/kg/infusion) or saline for 10 days (9 h/day); each infusion was paired with a cue light. Rats were then given 10 days of extinction during which the heroin and saline syringes were removed. Next, a test for reinstatement was conducted after exposure to 0 (baseline) or 1-day food deprivation. During training, lever pressing for heroin increased over days, while responding for saline infusions paired with the cue light decreased over time. During extinction, responding on the heroin-paired lever decreased over time, while responding on the saline-paired lever remained low. In heroin-trained rats, food deprivation induced a large increase in responding on the lever associated with drug infusions. Surprisingly, food deprivation also modestly increased responding in the saline-trained rats. Food deprivation selectively increased c-Fos immunoreactivity (IR) in the prelimbic cortex of heroin-trained, but not saline-trained, rats (n=4 per condition). Food deprivation also increased c-Fos IR in both heroin- and saline-trained rats in the basolateral amygdala and the ventrolateral bed nucleus of stria terminalis (BNST), but had no effect on c-Fos expression in the dorsolateral BNST, cingulate cortex, nucleus accumbens, and central amygdala. These results raise the possibility that the prelimbic cortex is involved in food deprivation-induced reinstatement of heroin seeking.

Animals↗

PubMed2003

Diadenosine tetraphosphate protects against injuries induced by ischemia and 6-hydroxydopamine in rat brain.

Diadenosine tetraphosphate (AP4A), an endogenous diadenosine polyphosphate, reduces ischemic injury in the heart. In this study, we report the potent and protective effects of AP4A in rodent models of stroke and Parkinson's disease. AP4A, given intracerebroventricularly before middle cerebral artery (MCA) ligation, reduced cerebral infarction size and enhanced locomotor activity in adult rats. The intravenous administration of AP4A also induced protection when given early after MCA ligation. AP4A suppressed terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) induced by hypoxia/reperfusion in primary cortical cultures, and reduced both ischemia-induced translocation of mitochondrial cytochrome c and the increase in cytoplasmic caspase-3 activity in vivo. The purinergic P2/P4 antagonist di-inosine pentaphosphate or P1-receptor antagonist sulfonylphenyl theophylline, but not the P2-receptor antagonist suramin, antagonized the effect of AP4A, suggesting that the observed protection is mediated through an anti-apoptotic mechanism and the activation of P1- and P4-purinergic receptors. AP4A also afforded protection from toxicity induced by unilateral medial forebrain bundle injection of 6-hydroxydopamine (6-OHDA). One month after lesioning, vehicle-treated rats exhibited amphetamine-induced rotation. Minimal tyrosine hydroxylase immunoreactivity was detected in the lesioned nigra or striatum. No KCl-induced dopamine release was found in the lesioned striatum. All of these indices of dopaminergic degeneration were attenuated by pretreatment with AP4A. In addition, AP4A reduced TUNEL in the lesioned nigra 2 d after 6-OHDA administration. Collectively, our data suggest that AP4A is protective against neuronal injuries induced by ischemia or 6-OHDA through the inhibition of apoptosis. We propose that AP4A may be a potentially useful target molecule in the therapy of stroke and Parkinson's disease.

Animals↗

PubMed2003

The endogenous cannabinoid anandamide inhibits alpha7 nicotinic acetylcholine receptor-mediated responses in Xenopus oocytes.

The effect of the endogenous cannabinoid ligand anandamide on the function of the cloned alpha7 subunit of the nicotinic acetylcholine (ACh) receptor expressed in Xenopus oocytes was investigated by using the two-electrode voltage-clamp technique. Anandamide reversibly inhibited nicotine (10 microM) induced-currents in a concentration-dependent manner (10 nM to 30 microM), with an IC50 value of 229.7 +/- 20.4 nM. The effect of anandamide was neither dependent on the membrane potential nor meditated by endogenous Ca2+ dependent Cl- channels since it was unaffected by intracellularly injected BAPTA and perfusion with Ca2+-free bathing solution containing 2 mM Ba2+. Anandamide decreased the maximal nicotine-induced responses without significantly affecting its potency, indicating that it acts as a noncompetitive antagonist on nicotinic acetylcholine (nACh) alpha7 receptors. This effect was not mediated by CB1 or CB2 receptors, as neither the selective CB1 receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride (SR 141716A) nor CB2 receptor antagonist N-((1S)-endo-1,3,3-trimethyl-bicyclo-heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR 144528) reduced the inhibition by anandamide. In addition, inhibition of nicotinic responses by anandamide was not sensitive to either pertussis toxin treatment or to the membrane permeable cAMP analog 8-Br-cAMP (0.2 mM). Inhibitors of enzymes involved in anandamide metabolism including phenylmethylsulfonyl fluoride, superoxide dismutase, and indomethacin, or the anandamide transport inhibitor AM404 did not prevent anandamide inhibition of nicotinic responses, suggesting that anandamide itself acted on nicotinic receptors. In conclusion, these results demonstrate that the endogenous cannabinoid anandamide inhibits the function of nACh alpha7 receptors expressed in Xenopus oocytes in a cannabinoid receptor-independent and noncompetitive manner.

Animals↗

PubMed2003

Rewarding injections of the cholinergic agonist carbachol into the ventral tegmental area induce locomotion and c-Fos expression in the retrosplenial area and supramammillary nucleus.

Previously we found that intra-ventral tegmental injections of the cholinergic agonist carbachol induce reward; such injections induce conditioned place preference and rats learn quickly to self-administer carbachol directly into the ventral tegmental area (VTA). To determine what brain regions are activated by such rewarding injections we studied the expression of the transcription factor c-Fos in local and distant brain regions following ventral tegmental injections of carbachol in rats. We also measured locomotion induced by such injections. Carbachol injections into the VTA induced vigorous locomotion while carbachol injections into the regions 1 mm dorsal or 1 mm lateral to the VTA induced delayed attenuated locomotion. Ventral tegmental injections of carbachol induced c-Fos expression throughout the brain. Significant correlations between locomotion c-Fos positive nuclei were found in the retrosplenial area the posterior hypothalamus including the supramammillary nucleus. These results suggest that the retrosplenial area supramammillary nucleus may be parts of the circuitry for the reward triggered by ventral tegmental cholinergic stimulation.

Animals↗

PubMed2003

Enabling role of adenosine A1 receptors in adenosine A2A receptor-mediated striatal expression of c-fos.

When striatal neurons are strongly activated they produce adenosine, which activates nearby adenosine A1 receptors (A1Rs) and adenosine A2A receptors (A2ARs). Although the effects of A1R or A2AR activation on neural activity in the striatum have been examined separately, the effects of coactivating both receptors has not been investigated. Using c-Fos immunohistochemistry as an indicator of neural activity, we examined the effects of coactivation of A1Rs and A2ARs on neural activity and their mechanism of interaction in the caudate-putamen, nucleus accumbens (NAc) and prefrontal cortex in rats. Administration of a motor-depressant dose of the A2AR agonist CGS 21680 (0.5 mg/kg i.p.) did not significantly induce c-fos expression in any of these brain regions. Administration of a motor-depressant dose of the A1R agonist CPA (0.3 mg/kg, i.p.) produced a small but significant induction of c-fos expression only in the shell of the NAc. Coadministration of CGS 21680 and CPA produced a synergistic induction of c-fos expression in the caudate-putamen, cingulate cortex, and especially the NAc. In the shell of the NAc administration of CPA significantly decreased extracellular dopamine levels measured by in vivo microdialysis and blocked CGS 21680-induced increases in dopamine levels. Because it has been previously shown that activation of dopamine D2 receptors (D2Rs) by endogenous dopamine blocks A2AR-mediated c-fos expression, it is hypothesized that the enabling role of A1Rs in A2AR-mediated striatal c-fos expression is related to the A1R-mediated inhibition of dopamine release.

Adenosine↗