Journal of neurophysiology
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In rat olfactory bulb slices, external tufted (ET) cells spontaneously generate spike bursts. Although ET cell bursting is intrinsically generated, its strength and precise timing may be regulated by synaptic input. We tested this hypothesis by analyzing whether the burst properties are modulated by activation of ionotropic gamma-aminobutyric acid (GABA) and glutamate receptors. ⋯ The GABA(A) agonist (isoguvacine, 10 microM) completely inhibited bursting or reduced the number of spikes/burst, suggesting a shunting effect. These findings indicate that the properties of ET cell spontaneous bursting are differentially controlled by GABAergic and glutamatergic fast synaptic transmission. We suggest that ET cell excitatory and inhibitory inputs may be encoded as a change in the pattern of spike bursting in ET cells, which together with mitral/tufted cells constitute the output circuit of the olfactory bulb.
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Human neck muscles have a complex multi-layered architecture. The role and neural control of these neck muscles were examined in nine seated subjects performing three series of isometric neck muscle contractions: 50-N contractions in eight fixed horizontal directions, 25-N contractions, and 50-N contractions, both with a continuously changing horizontal force direction. Activity in the left sternocleidomastoid, trapezius, levator scapulae, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles was measured with wire electrodes inserted at the C(4)/C(5) level under ultrasound guidance. ⋯ The current results demonstrate that all neck muscles can exhibit phasic activity during isometric neck muscle contractions. Similar oscillations in the EMG of neck muscles from different layers further suggest that neck motoneurons were activated by common neurons. The reticular formation appears a likely generator of the common drive to the neck motoneurons due to its widespread projections to different groups of neck motoneurons.
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The retrotrapezoid nucleus (RTN) contains central respiratory chemoreceptors that are inhibited by activation of slowly adapting pulmonary stretch receptors (SARs). Here we examine whether RTN inhibition by lung inflation could be mediated by a direct projection from SAR second-order neurons (pump cells). Pump cells (n = 56 neurons, 13 rats) were recorded in the nucleus of solitary tract (NTS) of halothane-anesthetized rats with intact vagus nerves. ⋯ This work confirms that many rat NTS pump cells are located in and around the interstitial subnucleus at area postrema level. We demonstrate that a GABAergic subset of these pump cells innervates the RTN region. We conclude that these inhibitory neurons probably contact RTN chemoreceptors and mediate their inhibition by lung inflation.
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The current study has investigated the involvement of periaqueductal gray (PAG) metabotropic glutamate subtype 7 and 8 receptors (mGluR(7) and mGluR(8)) in modulating rostral ventromedial medulla (RVM) ongoing and tail flick-related on and off cell activities. Our study has also investigated the role of PAG mGluR(7) on thermoceptive threshold and PAG glutamate and GABA release. Intra-ventrolateral PAG (S)-3,4-dicarboxyphenylglycine [(S)-3,4-DCPG (2 and 4 nmol/rat)] or N,N(I)-dibenzhydrylethane-1,2-diamin dihydrochloride (AMN082, (1 and 2 nmol/rat), selective mGluR(8) and mGluR(7) agonists, respectively, caused opposite effects on the ongoing RVM on and off cell activities. ⋯ A decrease in GABA release was also observed. These results show that stimulation of PAG mGluR(8) or mGluR(7) could either relieve or worsen pain perception. The opposite effects on pain behavior correlate with the opposite roles played by mGluR(7) and mGluR(8) on glutamate and GABA release and the ongoing and tail flick-related activities of the RVM on and off cells.
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This study examines motor cortical representation of hand position and its relationship to the representation of hand velocity during reaching movements. In all, 978 motor cortical neurons were recorded from the proximal arm area of rostral motor cortex. The results demonstrate that position and velocity are simultaneously encoded by single motor cortical neurons in an additive fashion and that the relative weights of the position and velocity signals change dynamically during reaching. ⋯ A new reaching task (standard reaching) is introduced to minimize these correlations. Likewise, a new decoding method (indirect OLE) was developed to analyze the data by simultaneously decoding both three-dimensional (3D) hand position and 3D hand velocity from correlated neural activity. This method shows that, on average, the reconstructed velocity led the actual hand velocity by 122 ms, whereas the reconstructed position signal led the actual hand position by 81 ms.