RESUMO
OBJECTIVE: The diagnosis of bipolar disease frequently requires a long time since the age of onset, especially because the disease is misdiagnosed with schizophrenia. The aim of the present work was to investigate whether sera from bipolar patients have an active substance that allows making a fast identification of the disease. METHODS: Sera from healthy volunteers, euthymic and non-stabilized bipolar patients, and schizophrenic patients were passively transferred into CF1 mice and after 2 day injections, MEPP frequency from diaphragm muscles was recorded. The same procedure was performed with sera fraction of high and low MW (cut-off 3000). RESULTS: Sera from non-stabilized bipolar patients induced a decreased MEPP frequency and occluded the presynaptic inhibitory effect of the specific adenosine A(1) receptor agonist 2-chloro-N(6)-cyclopentyl-adenosine (CCPA) in the recipient mice, while in the euthymic bipolar group spontaneous secretion reached control values although the action of CCPA was still prevented. Similar results were obtained with low MW sera fraction from euthymic and non-stabilized bipolar patients. The addition of adenosine deaminase to the sera fraction prevented the modification of spontaneous ACh release. In mice injected with sera from schizophrenic patients, MEPP frequency was within control values and CCPA induced its typical inhibitory action. CONCLUSIONS: These results indicate that bipolar patients contain in their blood an active substance compatible with adenosine, which was able to modify spontaneous ACh release in the recipient mice. This effect was not observed with sera from healthy volunteers and schizophrenic patients. The increase of adenosine concentration may result from synaptic hyperactivity that presumably plays a role in the symptoms of bipolar disorder and/or may derive from peripheral cells through a more general mechanism. SIGNIFICANCE: The different results obtained with bipolar and schizophrenic sera raise the possibility that the passive transfer model could be used as a diagnostic test in the future.
Assuntos
Acetilcolina/metabolismo , Transtorno Bipolar/sangue , Junção Neuromuscular/fisiologia , Esquizofrenia/sangue , Adenosina/análogos & derivados , Adenosina/farmacologia , Adulto , Análise de Variância , Animais , Diafragma/efeitos dos fármacos , Diafragma/inervação , Diafragma/fisiologia , Potencial Evocado Motor/efeitos dos fármacos , Potencial Evocado Motor/fisiologia , Feminino , Humanos , Técnicas In Vitro , Masculino , Camundongos , Pessoa de Meia-Idade , Junção Neuromuscular/efeitos dos fármacosRESUMO
1. At the mouse neuromuscular junction, adenosine (AD) and the A(1) agonist 2-chloro-N(6)-cyclopentyl-adenosine (CCPA) induce presynaptic inhibition of spontaneous acetylcholine (ACh) release by activation of A(1) AD receptors through a mechanism that is still unknown. To evaluate whether the inhibition is mediated by modulation of the voltage-dependent calcium channels (VDCCs) associated with tonic secretion (L- and N-type VDCCs), we measured the miniature end-plate potential (mepp) frequency in mouse diaphragm muscles. 2. Blockade of VDCCs by Cd(2+) prevented the effect of the CCPA. Nitrendipine (an L-type VDCC antagonist) but not omega-conotoxin GVIA (an N-type VDCC antagonist) blocked the action of CCPA, suggesting that the decrease in spontaneous mepp frequency by CCPA is associated with an action on L-type VDCCs only. 3. As A(1) receptors are coupled to a G(i/o) protein, we investigated whether the inhibition of PKA or the activation of PKC is involved in the presynaptic inhibition mechanism. Neither N-(2[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide (H-89, a PKA inhibitor), nor 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine (H-7, a PKC antagonist), nor phorbol 12-myristate 13-acetate (PHA, a PKC activator) modified CCPA-induced presynaptic inhibition, suggesting that these second messenger pathways are not involved. 4. The effect of CCPA was eliminated by the calmodulin antagonist N-(6-aminohexil)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7) and by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-acetoxymethyl ester epsilon6TDelta-BM, which suggests that the action of CCPA to modulate L-type VDCCs may involve Ca(2+)-calmodulin. 5. To investigate the action of CCPA on diverse degrees of nerve terminal depolarization, we studied its effect at different external K(+) concentrations. The effect of CCPA on ACh secretion evoked by 10 mm K(+) was prevented by the P/Q-type VDCC antagonist omega-agatoxin IVA. 6. CCPA failed to inhibit the increases in mepp frequency evoked by 15 and 20 mm K(+). We demonstrated that, at high K(+) concentrations, endogenous AD occupies A1 receptors, impairing the action of CCPA, since incubation with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, an A(1) receptor antagonist) and adenosine deaminase (ADA), which degrades AD into the inactive metabolite inosine, increased mepp frequency compared with that obtained in 15 and 20 mm K(+) in the absence of the drugs. Moreover, CCPA was able to induce presynaptic inhibition in the presence of ADA. It is concluded that, at high K(+) concentrations, the activation of A(1) receptors by endogenous AD prevents excessive neurotransmitter release.
Assuntos
Acetilcolina/metabolismo , Adenosina/farmacologia , Junção Neuromuscular/metabolismo , Terminações Pré-Sinápticas/metabolismo , Acetilcolina/antagonistas & inibidores , Agonistas do Receptor A1 de Adenosina , Animais , Relação Dose-Resposta a Droga , Masculino , Camundongos , Junção Neuromuscular/efeitos dos fármacos , Terminações Pré-Sinápticas/efeitos dos fármacos , Receptor A1 de Adenosina/metabolismoRESUMO
OBJECTIVES: The aim of this work was to further investigate the effect of sera from sporadic amyotrophic lateral sclerosis (ALS) patients on miniature end-plate potentials (MEPP) frequency, by the mouse passive transfer model, and to study whether the transferred serum induces any change in the sensitivity of the L-type voltage-dependent calcium channels (VDCC) to its specific blocker Nitrendipine. METHODS: A total of 35 CF1 mice were divided into 3 groups: (a) ALS group receiving sera from 15 patients that had been clinically and electromyographycally diagnosed as having sporadic ALS; (b) normal group receiving sera from 13 healthy volunteers and from 3 disease control patients, and (c) control group, which was kept untreated. Animals in groups (a) and (b) received daily intraperitoneal injection of 0.5-1ml of serum for 3 days, and 24h later the left hemidiaphragm was excised for electrophysiological recordings. RESULTS: Analysis of MEPPs frequency recorded from ALS group showed that 3 of them induced an increase in spontaneous neurotransmitter release while in 4 a decrease was observed, suggesting that sera alter spontaneous secretion as result of an increased or decreased Ca(2+) influx through the normally involved N-type or L-type VDCC, respectively. When the effect of Nitrendipine, an L-type VDCC blocker, was studied on ALS sera-injected mice, we found variable responses to the drug: only two mice showed control sensitivity to Nitrendipine, while in 7 its action was lower and surprisingly in 4 was greater than that without the drug. CONCLUSIONS: These results suggest that ALS sera contain factor(s) that are able to modify spontaneous neurotransmitter release by altering calcium current through L-type and N-type VDCC, and even inducing changes in the sensitivity to the L-type VDCC blocker.