Janice Henriques da Silva

The effect of sevoflurane on the release of [3H]dopamine from rat brain cortical slices.

Dopamine is a neurotransmitter that exerts major control on important brain functions and some lines of studies suggest that dopaminergic neurotransmission may be a potential target for volatile anesthetics. In the present study, rat brain cortical slices were labeled with [(3)H]dopamine to investigate the effects of sevoflurane on the release of this neurotransmitter. [(3)H]dopamine release was significantly increased in the presence of sevoflurane (0.46 mM) and this effect was independent of extracellular or intracellular calcium. In addition, [(3)H]dopamine release evoked by sevoflurane was not affected by TTX (blocker of voltage-dependent sodium channels) or reserpine (a blocker of the vesicular monoamine transporter). These data suggest that the dopamine release induced by sevoflurane is non-vesicular, independent of exocytosis and, would be mediated by the dopamine transporter (DAT). GBR12909 and nomifensine, inhibitors of DAT, decreased the release of [(3)H]dopamine evoked by sevoflurane. The same effect was also observed when the brain cortical slices were incubated at low temperature and low extracellular sodium. Ouabain, a Na(+)/K(+) ATPase pump inhibitor, which is known to induce dopamine release through reverse transport, decreased [(3)H]dopamine release induced by sevoflurane. In conclusion, the present study suggests that sevoflurane increases [(3)H]dopamine release in brain cortical slices that is mediated by DAT located at the plasma membrane.

Halothane induces vesicular and carrier-mediated release of [3H]serotonin from rat brain cortical slices.

The serotonergic system may play a role during general anesthesia but the effect of the volatile anesthetic halothane on the release of serotonin (5-HT) is not fully understood. Rat brain cortical slices were labeled with [3H]5-HT to investigate the effects of halothane on the release of this neurotransmitter from the central nervous system. Halothane induced an increase on the release of [3H]5-HT that was dependent on incubation time and anesthetic concentration (0.006, 0.012, 0.024, 0.036, 0.048 and 0.072 mM). This effect was independent of extracellular calcium and was not affected by tetrodotoxin (blocker of voltage dependent Na+ channels). In contrast, the halothane-evoked [3H]5-HT release was reduced by BAPTA-AM, a membrane-permeable BAPTA analog that chelates intracellular Ca2+. The anesthetic-induced [3H]5-HT release depends on the ryanodine-sensitive intracellular calcium store since it was blocked by dantrolene and azumolene (inhibitors of the calcium-release through ryanodine receptors) but was not affected by aminoethoxydiphenylborate (2-APB), an inhibitor of inositol 1,4,5-triphosphate receptor. The [3H]5-HT release induced by halothane comes mainly from the vesicular pool since it was reduced in about 70% by reserpine, a blocker of vesicular monoamine transporter. The halothane-evoked release of [3H]5-HT release is reduced by fluoxetine, an inhibitor of 5-HT uptake, and the volatile agent also decreased the uptake of [3H]5-HT into rat brain cortical slices. Moreover, a decrease on halothane-induced release of [3H]5-HT was also observed when the brain cortical slices were incubated at low temperature, which is known to interfere with the carrier-mediated release of the neurotransmitter. Ouabain, a Na+/K+ ATPase pump inhibitor, which induces 5-HT release through reverse transport, also decreased [3H]5-HT release induced by halothane, confirming the involvement of a carrier-mediated release of the neurotransmitter in the presence of halothane. In conclusion, these data suggest that halothane induces vesicular and carrier-mediated release of [3H]5-HT in rat brain cortical slices.

The effect of sevoflurane on intracellular calcium concentration from cholinergic cells

The mechanism of action of volatile anesthetics is not completely understood. Calcium release from internal stores may alter signaling pathways that influence neurotransmission. Abnormalities of the regulation of intracellular calcium concentration ([Ca2+]i) from patients with malignant hyperthermia is a hallmark of this syndrome indicating the potential of these agents to interact with proteins involved in Ca2+ signaling. In the present study, a cholinergic cell line (SN56) was used to examine whether the release of calcium from intracellular stores occurs in the presence of sevoflurane. Changes in [Ca2+]i were measured using fluo-4, a fluorescent calcium sensitive dye and laser scanning confocal microscopy. Sevoflurane induced an increase on [Ca2+]i from SN56 cells. The sevoflurane-induced increase on [Ca2+]i remained even when the cells were perfused with medium lacking extracellular calcium. However, this effect was abolished by BAPTA-AM, a chelator of intracellular calcium, suggesting the involvement of intracellular Ca2+ stores. Using cyclopiazonic acid, an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, we investigated whether the depletion of intracellular Ca2+ stores interfered with the effect of sevoflurane. In the presence of this agent, sevoflurane caused a small but not significant rise on [Ca2+]i of the SN56 cells. Dantrolene, an inhibitor of ryanodine-sensitive calcium stores did not modify the sevoflurane increase on [Ca2+]i. Carbachol, a drug that releases Ca2+ from the IP3 pool, abolished the effect of sevoflurane. In addition, xestospongin D, a cell-permeant IP3 receptor antagonist, decreased significantly the sevoflurane increase on [Ca2+]i. Our data suggest that the sevoflurane-induced increase on [Ca2+]i from SN56 cells occurs through the release of calcium from IP3-sensitive calcium stores.

Acetylcholine release induced by the volatile anesthetic sevoflurane in rat brain cortical slices.

Summary1.We have investigated the effect of the volatile anesthetic sevoflurane on acetylcholine (ACh) release from rat brain cortical slices.2.The release of [3H]-ACh into the incubation fluid was studied after labeling the tissue ACh with [methyl-3H]-choline chloride.3.We observed that sevoflurane induced an increase on the release of ACh that was dependent on incubation time and anesthetic concentration. The sevoflurane-induced ACh release was not blocked by tetrodotoxin (TTX) and therefore was independent of sodium channels. In addition, the sevoflurane effect was not blocked by ethylene glycol-bis(β-aminoethyl ether (EGTA) or cadmium (Cd2+), thus independent of extracellular calcium.4.The sevoflurane-induced ACh release was inhibited by 1,2-bis (2-aminophenoxy) ethane-N,N,N’,N’-tetra-acetic acid (BAPTA-AM), suggestingthe involvement of intracellular calcium-sensitive stores in the process. Dantrolene, an inhibitor of ryanodine receptors, had no effect but 2-aminoethoxydiphenylborate (2-APB), a membrane-permeable inhibitor of inositol 1,4,5-triphosphate receptor inhibited the sevoflurane-induced release of ACh.5.It is concluded that sevoflurane-induced release of ACh in brain cortical slices involves the mobilization of calcium from IP_{3}-sensitive calcium stores.

Analysis of Anatomical Characteristics and Morphometric Aspects of Infraorbital and Accessory Infraorbital Foramina

Objective: This study aimed to perform a morphological and morphometric study of the characteristics of the infraorbital foramen (IOF) and accessory infraorbital foramen (AIOF) in Brazilian skulls. Methods: A sample calculation determined a total of 94 human skulls to be evaluated by a trained examiner for number, shape, diameters, and location of IOF in relation to anatomical landmarks. Number, size, shape, diameters, location, orientation, position, and distances in relation to anatomical landmarks were evaluated for the AIOF. Descriptive analysis, paired t test, Wilcoxon test, Pearson and Spearman correlations were used. Results: A total of 188 IOFs and 48 AIOFs were found. Circular outline was the predominant shape for both IOFs and AIOFs. Infraorbital foramens presented in left sides had a significantly greater transverse diameter and distance from medial margin of the orbit when compared with IOFs located on the right sides (P <0.001). Accessory infraorbital foramens were most frequently found on the left sides of the skulls and had a superomedial position in relation to the IOFs. Accessory infraorbital foramens located on right sides had a significantly greater distance to anterior nasal spine when compared with AIOFs located on the left sides (P <0.001). Conclusions: The results of this solid methodology-based study can help guide surgeons in accurately locating the IOF and AIOF, and consequently, their neurovascular bundles to perform safe procedures during maxillofacial interventions.

Comparative presynaptic effects of the volatile anesthetics sevoflurane and isoflurane at the mouse neuromuscular junction.

Introduction: Sevoflurane and isoflurane are anesthetics that cause muscle relaxation and potentiate the effects of neuromuscular blocking agents. Their presynaptic mechanisms of action are not understood completely, especially at the motor nerve terminal. Methods: We compared the presynaptic effects of these anesthetics on the exocytosis of synaptic vesicles labeled with the dye FM1–43 at the mouse neuromuscular junction. Results: Neither anesthetic evoked spontaneous exocytosis of synaptic vesicles, but both significantly inhibited the depolarization evoked by 4‐aminopyridine and veratridine, suggesting a putative action on sodium channels. Exocytosis evoked by veratridine was inhibited by tetrodotoxin alone or in conjunction with sevoflurane or isoflurane, indicating that both agents may target voltage‐gated sodium channels. Conclusions: We suggest that sevoflurane and isoflurane inhibit exocytosis evoked by sodium‐dependent depolarization and might act on tetrodotoxin‐sensitive sodium channels. These findings contribute to a better understanding of some clinical neuromuscular effects induced by these anesthetics. Muscle Nerve 52: 876–884, 2015

O ensino-aprendizagem da anatomia humana: avaliação do desempenho dos alunos após a utilização de mapas conceituais como uma estratégia pedagógica

EnglishAbstract The aim of this study was to implement and evaluate the impact of the development of Concept Maps (MC), as a pedagogical strategy in teaching of Human Anatomy, one of the course subjects of Physical Therapy, from Federal University of Minas Gerais (UFMG). A total of 298 students, enrolled regularly, participated of the study over six semesters. The mean analysis of the final scores of the students, prior to the expansion of the MC Project, showed decrease of average score over the semester, which was reversed when the MC were implemented systematically. The implementation of MC were also capable of promoting a significant reduction in the failure rate. Thus, we conclude that the use of MC seems to have contributed to improving student performance and also the approval rating in the discipline of Anatomy, especially after the systematization of its use by the Teaching Project supported by the institution. portuguesResumo O objetivo deste estudo foi implementar e avaliar o impacto da elaboracao de Mapas Conceituais (MC) como estrategia pedagogica no ensino-aprendizagem da Anatomia Humana, uma das disciplinas do curso de Fisioterapia da Universidade Federal de Minas Gerais. Participaram do estudo 298 alunos regularmente matriculados, ao longo de seis semestres. A analise das medias das notas finais dos alunos, anteriores a ampliacao do projeto dos MC, demonstrou decrescimo dessas medias ao longo dos semestres, o que foi revertido quando o projeto de ensino de MC foi implementado sistematicamente. A implementacao dos MC tambem foi capaz de promover uma reducao significativa no indice de reprovacao. Assim, concluimos que o uso de MC parece ter contribuido para melhorar o desempenho dos alunos e tambem o indice de aprovacao na disciplina de Anatomia Humana, principalmente apos a sistematizacao do seu uso atraves do Projeto de Ensino apoiado pela Pro-Reitoria de Graduacao da Instituicao.