Spontaneous firing in olfactory bulb neurons of Bufo bufo gargarizans in and after hibernation

Microelectrode technique was used to record the spontaneous electrical activities of the neurons in olfactory bulb of the Bufo bufo gargarizans, both in hibernation and after hibemation. This study investigated the electrophysiological characteristics of amphibian olfactory bulb in the period of hibernation and after hibernation and its effects on the start of hibernation and spontaneous awakening. The research showed four forms of spontaneous firings： single spontaneous firing, burst spontaneous firing, irregular spontaneous firing and consecutive single spontaneous firing. The single spontaneous firing includes slow depolarized spontaneous firing and fast depolarized spontaneous firing, and the slow depolarized spontaneous firing occurs only during the hibernation period. In hibernation, the low amplitude and low frequency firing with a longer duration may be relevant to maintaining the tonicity of the central nervous system in toads that are in hibernation, and this kind of firing may also provide an excited basis for their arousal from hibernation. After hibernation, the amplitude and frequency of firing increase, but the firing duration gets shorter. This form of short-term firing, which may be a phenomenon of sensory neurons fast adapting, is one of the neuronal mechanisms for the arousal of hibernating animals.

A comparison of the spontaneous firing patterns between principal cells and fast spiking interneurons from dentate gyrus in waking guinea pigs

Objective To explore the possible mechanisms that cause the dentate gyrus （DG） neurons to play different roles in information coding. Methods In vivo extracellular single unit recording was performed on 22 waking female guinea pigs, which were positioned in a sound-attenuated recording chamber without any muscular relaxants. The spontaneous firing patterns of the DG neurons were detected and compared. Results There were two different electrophysiologi- cal populations in the DG of guinea pigs, principal cells （PCs） and fast spiking interneurons （INs）. Of the PCs, 1.3% discharged regularly, 48.1% irregularly and 50.6% in bursts ; in contrast, of the INs units, 64.1% discharged regularly, 2.6% irregularly and 33.3% in bursts. The spontaneous firing patterns of PCs were significantly different from those of INs （P 〈0.01 ）. In addition, the differences of several interspike interval （ISI） parameters also have been observed： （1） the ISI coefficients of variation of PCs （3.39 ± 3.56） were significantly higher than those of INs （1.08 ± 0.46） （P 〈0.01） ; （2） the ISI asymmetric indexes of PCs （0. 047±0. 059） were significantly lower than those of INs （0.569±0. 238） （P 〈 0.01 ）. Conclusion In the DG, the spontaneous firing patterns of PCs were significantly different from those of INs. The former were prone to fire in bursts, the latter were prone to fire regularly. The different roles in information coding between PCs and INs might be caused by their different firing patterns.

Spontaneous firing properties of rat medial vestibular nucleus neurons in brain slices by infrared visual patch clamp technique

Domestic application of infrared patch clamp techniques on brain slices is limited.The key of the tech-nique is to prepare high-quality brain slices.The present paper describes the preparation procedure of brainstem slices and the spontaneous firing properties of rat medial vestibular nucleus(MVN)neurons.By infrared differ-ential interference contrast technique,neurons of rat MVN were visualized directly at the depth of 50–100 mm underneath the surface of slices.Firing activities of MVN neurons were recorded by the whole-cell patch clamp technique in artificial cerebrospinal fluid(ACSF)and low Ca^(2+)-high Mg^(2+) fluid.The firing mode was more irregular and depressive in low Ca^(2+)-high Mg2+fluid than in ACSF.According to the averaged waveform of action potentials,cells were classified as the neurons with mono-phasic after-hyperpolarization potential(AHP),and the neurons with biphasic AHP.The resting membrane potential(RMP),input resistance(Rin)and membrane capacitance(Cm)of neurons were recorded and com-pared between groups.With infrared videomicroscopy,patch clamp recordings could be made under direct obser-vation in freshly prepared brainstem slices.The discharge activities of MVN neurons were spontaneous and the fir-ing mode was modulated by extracellular calcium concen-tration.The basic membrane properties of two types of neurons were not significantly different,while the differ-ences in waveform might play a role in the segregation between tonic and kinetic cells.

Designing coal panels in the conditions of associated methane and spontaneous fire hazards

An increase in methane,spontaneous fire and bumping hazards in Polish hard coal mines,observed in the last two decades,led to the need to elaborate the tools allowing proper selection of a range of preventive measures to fight them at the stage of designing coal extraction.Designing the production of a coal seams in the conditions of associated methane and spontaneous fires hazards in Polish hard coal mines requires elaboration of the design standards for coal panels in gassy coal seams.This paper presents the guidelines on how to design production in the conditions of associated methane and spontaneous fire hazards.Presented tools and methodology since the very first research were many times verified by daily mining operations in the conditions of associated methane and spontaneous fire hazards,which confirms their significant contribution to the development of safe and economical mining operations.

Analysis of underground fires in Polish hard coal mines

In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Investigations into the development of new methods of fire hazard prediction and implementation of new methods and means of fire prevention as well as the introduction of prohibition concerning the use of products manufactured of combustible organic materials in underground mine workings re-duced considerably the hazard of underground fire rise. The worked out at the Central Mining Institute (GIG) new method of un-derground fire prediction allows the correct selection of fire prevention means. The introduction into common use of fire-resistant conveyor belts, the main factor giving rise to spontaneous fires, and methods of assessment of their fire resistance eliminated prac-tically the fire hazard. These activities contributed in an efficient way to the reduction of the number of underground fires to a sat-isfactory level.

Sexual dimorphism of the electrophysiological properties of the projection neurons in the robust nucleus of the arcopallium in adult zebra finches

Objective To observe the sexual differences in electrophysiological properties of neurons in the robust nucleus of the arcopallium （RA） in adult zebra finches, and to provide the direct electrophysiological evidence for the sexual dimorphism of birdsong. Methods Whole-cell recording was used to record the spontaneous action potential firing rates from RA projection neurons in acute brain slices. Results The projection neurons of RA in male birds fired spontaneously at 10 Hz or above, while in female birds, the frequency was significantly lower, and even no firings could be detected. Conclusion There is a sexual difference in electrophysiological properties of projection neurons in RA, which may result from the difference in the levels of steroid hormones in birds.