Neuroscience
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The polypeptide ghrelin is an endogenous ligand at the growth hormone secretagogue receptor 1a. To ghrelin multiple functions have been ascribed including promotion of gastrointestinal motility. Postprandial ghrelin levels have been reported to be reduced in patients suffering from Parkinson disease (PD). ⋯ Whereas the protective effects of acylated ghrelin required receptor binding, effects of the unacylated form remained unaffected by treatment with a ghrelin receptor antagonist. Importantly, inhibition of ghrelin O-acyltransferase failed to reduce the activity of unacylated ghrelin. Overall, our data suggest that both acylated and unacylated ghrelin afford protection to dopamine neurons but through mechanisms that only partially overlap.
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Bradykinin (BK), a component of the kallikrein-kininogen-kinin system exerts multiple effects via B1 and B2 receptor activation. In the cardiovascular system, bradykinin has cardioprotective and vasodilator properties. We investigated the effect of BK on cardiac-projecting neurons of nucleus ambiguus, a key site for the parasympathetic cardiac regulation. ⋯ BK produced a dose-dependent depolarization of nucleus ambiguus neurons, which was prevented by the B2 receptor antagonist. In vivo studies indicate that microinjection of BK into nucleus ambiguus elicited bradycardia in conscious rats via B2 receptors. In summary, in cardiac vagal neurons of nucleus ambiguus, BK activates B2 receptors promoting Ca2+ influx and Ca2+ release from endoplasmic reticulum, and membrane depolarization; these effects are translated in vivo by bradycardia.
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Theta burst stimulation (TBS) has emerged as a promising tool for the treatment of swallowing disorders; however, the short-term after-effects of brain activation induced by TBS remain unknown. Here, we measured the changes in spontaneous brain activation using the amplitude of low-frequency fluctuation (ALFF) approach in subjects who underwent different TBS protocols. Sixty right-handed healthy participants (male, n=30; female, n=30; mean age=23.5y) were recruited in this study and randomly assigned to three groups that underwent three different TBS protocols. ⋯ These findings indicate that multiple brain areas involved in swallowing regulation after stimulation of TBS over the suprahyoid muscles. cTBS induces decreased after-effects while iTBS results in increased after-effects on spontaneous brain activation. Moreover, iTBS can eliminate the after-effects of cTBS applied on the contralateral swallowing cortex and alter the activity of contralateral motor cortex and brainstem. Our findings provide a novel evidence for the short-term effect of TBS on spontaneous brain activation.
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Little is known about how the central nervous system prepares postural responses differently in anticipated compared to non-anticipated perturbations. To investigate this, participants were exposed to translational and rotational perturbations presented in a blocked (anticipated) and a random (non-anticipated) design. The preparatory setting ('central set') was measured by H-reflexes, motor-evoked potentials (MEPs), and short-interval intracortical inhibition (SICI) shortly before perturbation onset in the soleus of 15 healthy adults. ⋯ As the SLR and MLR are organized at the spinal and the LLR at the cortical level, the preparatory setting seems to mainly influence cortically mediated postural responses. However, the modulation of the H-reflex before anticipated perturbations indicates that supraspinal centers adjusted Ia-afferent transmission for the soleus in a perturbation-specific manner. Intracortical inhibition was also modulated but differentiates to a lesser extent only between perturbation conditions and unperturbed stance.
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One of the earliest activities expressed within the developing central nervous system is a widely propagating wave-like activity, which we referred to as the depolarization wave. Despite considerable consensus concerning the global features of the activity, its physiological role is yet to be clarified. ⋯ Chronic inhibition of the depolarization wave had no significant effect on the developmental time course, amplitude, and spatial distribution of monosynaptic excitatory postsynaptic potentials in the first-order nuclei of the vagal sensory pathway (the nucleus of the tractus solitarius (NTS) and the contralateral non-NTS region), but reduced polysynaptic responses in the higher-order nucleus (the parabrachial nucleus). These results suggest that the depolarization wave plays an important role in the initial process of functional synaptic expression in the brainstem, especially in the higher-order nucleus of the cranial sensory pathway.