Neuroscience
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In the present study we combined FM 1-43 imaging and electrophysiological recording of miniature end-plate currents (MEPCs) to determine the role of extracellular calcium in synaptic vesicle exo- and endocytosis at the frog motor nerve terminals. We replaced extracellular Ca2+ ions with other bivalent cations (Sr2+, Ba2+, Cd2+, Mg2+) or used a calcium-free solution and monitored fluorescent staining of the nerve terminals in the presence of caffeine, which promotes the release of Ca2+ from intracellular stores. Caffeine has induced FM1-43 internalization only in the presence of bivalent cations in the external solution. ⋯ This effect of a calcium-free solution was not due to a decrease in exocytosis, because caffeine-induced FM1-43 unloading from the previously loaded nerve terminals, as well as a degree of the MEPCs frequency increase, was unchanged. We conclude that the presence of Ca2+ or other bivalent cations in extracellular space is necessary for endocytosis but not for exocytosis of synaptic vesicles, while transmitter release is promoted by efflux of Ca2+ from intracellular stores. The effect of extracellular Ca2+ on endocytosis might be driven by the non-specific interactions with membrane lipids.
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In the rodent, arcuate nucleus of the hypothalamus (ARH)-derived neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons have efferent projections throughout the hypothalamus that do not fully mature until the second and third postnatal weeks. Since this process is likely completed by birth in primates we characterized the ontogeny of NPY and melanocortin systems in the fetal Japanese macaque during the late second (G100), early third (G130) and late third trimesters (G170). NPY mRNA was expressed in the ARH, paraventricular nucleus (PVH), and dorsomedial nucleus of the hypothalamus (DMH) as early as G100. ⋯ In addition, cocaine and amphetamine-related transcript (CART) and alpha-melanocyte stimulating hormone (alphaMSH) were not colocalized in fibers or cell bodies. As a consequence of the prenatal development of these neuropeptide systems in the NHP, the maternal environment may critically influence these circuits. Additionally, because differences exist in the neuroanatomy of NPY and melanocortin circuitry the regulation of these systems may be different in primates than in rodents.
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Men are typically reported to have higher pain thresholds than women. Gonadal hormones, particularly testosterone for males, may contribute to this effect. This study tested whether changes in the male hormonal milieu early or late in development alter the inflammatory pain induced by carrageenan (CARR, 3%, intraarticular). ⋯ Both doses of morphine increased mechanical and thermal thresholds. However, compared with the control group, 1 mg/kg morphine was equally effective in reducing mechanical hyperalgesia among groups of animals gonadectomized as adults, but less effective in males gonadectomized neonatally. The results suggest that in males: 1. the antihyperalgesic effect of testosterone (or its metabolites) in CARR-induced inflammation is established during development and maintained by circulating levels of testosterone in adulthood; 2. the nociception-related interaction between the opioid and gonadal systems influences the sensitivity to mechanical stimuli and is likely established during the period of sexual differentiation.
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In the adult CNS, GABA is the predominant inhibitory neurotransmitter, mediating the hyperpolarization of membrane potential and regulating the glutamatergic activity. In the immature CNS, on the other hand, GABA mediates depolarization and is involved in controlling morphogenesis. This developmental shift in GABA actions from depolarization to hyperpolarization occurs as a result of decreasing the intracellular chloride ion (Cl(-)) concentration ([Cl(-)](i)) which is regulated by the potassium (K(+))-Cl(-) co-transporter 2 (KCC2). ⋯ As development proceeded, the number of KCC2-positive granule cells increased, and all granule cells became positive by P21. These results suggested that GABAergic transmission on granule cells might shift from excitation to inhibition after the synapse formation, and the excitatory synapse-formation and related factors might be the triggers for the expression and localization of the KCC2 in the granule cells. Furthermore, it was also suggested that formation of the GABAergic synapses and GABAergic transmission were not necessary for the KCC2-expression in the mouse cerebellar granule cells in vivo.
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Superoxide produced by the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediates crucial intracellular signaling cascades in the medial nucleus of the solitary tract (mNTS), a brain region populated by catecholaminergic neurons, as well as astroglia that play an important role in autonomic function. The mechanisms mediating NADPH oxidase (phagocyte oxidase) activity in the neural regulation of cardiovascular processes are incompletely understood, however the subcellular localization of superoxide produced by the enzyme is likely to be an important regulatory factor. We used immunogold electron microscopy to determine the phenotypic and subcellular localization of the NADPH oxidase subunits p47(phox), gp91(phox,) and p22(phox) in the mNTS in rats. ⋯ These results indicate that NADPH oxidase assembly and consequent superoxide formation are likely to occur near the plasmalemma, as well as on vesicular organelles associated with intracellular calcium storage within mNTS neurons and glia. Thus, NADPH oxidase-derived superoxide may participate in intracellular signaling pathways linked to calcium regulation in diverse mNTS cell types. Moreover, NADPH oxidase-derived superoxide in neurons and glia may directly or indirectly modulate catecholaminergic neuron activity in the mNTS.