Discharge profiles of spontaneous and non-spontaneous EVN neurons.

<p><b>(A)</b> Schematic view of transversely sectioned mouse brainstem. Inset shows map of recording sites from a subset of EVN neurons (37/54 recorded neurons). <i>VN</i>: vestibular nucleus; <i>G7n</i>: genu of seventh cranial nerve (facial nerve); <i>6n</i>: sixth cranial nerve nucleus (abducens nucleus); <i>4V</i>: fourth ventricle; <i>EVN</i>: efferent vestibular nucleus. <b>(B)</b> EVN neurons are either spontaneous firing (<i>n</i> = 16) (<i>top trace</i>) or non-spontaneously firing (<i>n</i> = 38) (<i>bottom</i> trace) at resting membrane potential and display homogenous discharge profiles in response to depolarizing <b>(C)</b> and hyperpolarizing <b>(E)</b> step currents. EVN neurons respond with a short burst (*) of high frequency action potentials (AP) at the onset of a depolarizing stimulus or the cessation of a hyperpolarizing stimulus. <b>(D)</b> Comparison of instantaneous frequencies as a function of injected depolarizing current from a subset of MVN and EVN neurons from which the slope of linear fit was used to calculate the gain of each neuron. *** <i>p</i><0.001. <b>(F)</b> EVN neurons displayed an afterdepolarization (ADP) following release from inhibition (arrow in <b>(E)</b>). The ADP was mediated by T-type calcium channels—TTX (1 μM) abolished all APs, and TTA-P2 (1 μM) abolished the remaining response.</p

Summary of passive membrane and action potential properties of spontaneous EVN, non-spontaneous EVN, and MVN neurons.

<p>All data are presented as means ± SD.</p><p>** <i>p</i><0.01 between spontaneous EVN neurons and MVN neurons</p><p>^†††<i>p</i><0.001 between non-spontaneous EVN neurons and MVN neurons</p><p>^‡‡‡<i>p</i><0.001 between spontaneous and non-spontaneous EVN neurons</p><p>Comparisons made using student’s unpaired <i>t</i>-test.</p><p>Summary of passive membrane and action potential properties of spontaneous EVN, non-spontaneous EVN, and MVN neurons.</p

EPSC and mIPSC properties.

<p><b>(A)</b> AMPA/kainate type glutamate receptor, GABA_AR and GlyR-mediated EPSCs and mIPSCs. <b>(B)</b> Averaged GABA_AR- and GlyR- mediated mIPSCs, and AMPA/kainate glutamate receptor mediated EPSC, isolated from the recordings shown above. <b>(C)</b> Bar graphs showing GABA_AR-, GlyR-mediated mIPSCs and AMPA/kainate glutamate receptor mediated EPSC amplitude, decay time, rise time, and width. * <i>p</i><0.05, ** <i>p</i><0.01. Values within bars indicate the number of cells sampled. Double diagonal lines indicate that EPSC and mIPSCs values are not compared, but are presented on same bar graph for ease of demonstration.</p

Identification and classification of excitatory and inhibitory profiles in EVN neurons.

<p><b>(A)</b> Schematic view of transversely sectioned mouse brainstem. Inset shows map of recording sites (22/23 recorded neurons). <i>VN</i>: vestibular nucleus; <i>G7n</i>: genu of seventh cranial nerve (facial nerve); <i>6n</i>: sixth cranial nerve nucleus (abducens nucleus); <i>4V</i>: fourth ventricle; <i>EVN</i>: efferent vestibular nucleus. <b>(B)</b><i>Top trace</i>: EPSCs recorded under normal conditions before the addition of drugs. <i>Second trace</i>: addition of CNQX (10 μM) and TTX (1 μM). <i>Third trace</i>: mIPSCs recorded under normal conditions before the addition of drugs. <i>Bottom trace</i>: addition of strychnine (1 μM) and bicuculline (10 μM) abolished all synaptic activity. Some neurons received excitatory inputs in conjunction with: GABA_AR-mediated events <b>(C)</b><i>Bottom trace</i>: addition of bicuculline to the bath abolished activity remaining after the addition of TTX and CNQX (<i>second trace</i>); GlyR-mediated events <b>(D)</b><i>Bottom trace</i>: addition of strychnine abolished remaining activity following the addition of TTX and CNQX (<i>second trace</i>). <b>(E)</b> Other neurons received a combination of mIPSCs in addition to EPSCs. In these neurons, the addition of bicuculline reduced the frequency of synaptic activity (<i>third trace</i>) that was abolished by addition of strychnine (<i>bottom trace</i>). Scale bar in <b>(B)</b> is the same for all traces. <b>(F)</b> Frequencies of EPSCs and mIPSCs per cell calculated over a period of 30 seconds under the influence of excitatory and inhibitory synaptic activity blockers.</p