probiotic-studies-in-neonatal-mice-using-gavage

Probiotic Studies in Neonatal Mice Using Gavage

Adult mouse models have been widely used to understand the mechanism behind disease progression in humans. The applicability of studies done in adult ...

University of British Columbia

Most of what is known regarding the actions of injectable barbiturate anesthetics on the activity of lumbar sensory neurons arises from experiments performed in acute animal preparations that are exposed to invasive surgery and neural depression caused by coadministered inhalational anesthetics. Other parameters such as cortical synchronization and motor ouflow are typically not monitored, and, therefore, anesthetic actions on multiple cellular systems have not been quantitatively compared.

Transmission through the dorsal spinocerebellar and spinoreticular tracts: wakefulness versus thiopental anesthesia.

Peripheral nerve-evoked potentials recorded in the cerebellum 35 yr ago inferred that sensory transmission via the dorsal spinocerebellar tract (DSCT) is reduced occasionally and only during eye movements of active sleep compared with wakefulness or quiet sleep. A reduction or withdrawal of primary afferent input and/or ongoing inhibition of individual lumbar DSCT neurons may underlie this occurrence. This study distinguished between these possibilities by examining whether peripheral nerve-evoked responses recorded from individual DSCT neurons are suppressed specifically during active sleep, and if so, whether GABA mediates this phenomenon. Synaptic responses to threshold stimuli applied to the sciatic nerve were characterized by a single spike response at short latency and/or a longer latency burst of action potentials. During the state of quiet wakefulness, response magnitude did not differ from that observed during quiet sleep. During active sleep, short and long latency responses were suppressed by 26 and 14%, respectively, and returned to pre-active sleep levels following awakening from active sleep. Sciatic nerve-evoked early and late responses were further analyzed in a paired fashion around computer-tagged eye movement events that hallmark the state of active sleep. Response magnitude was suppressed by 14.4 and 11.5%, respectively, during eye movement events of active sleep. The GABA(A) antagonist bicuculline, applied juxtacellularly by microiontophoresis, abolished response suppression during non-eye movement periods and eye movement events of active sleep. In conclusion, synaptic transmission via DSCT neurons is inhibited by GABA tonically during non-eye movement periods and phasically during eye movement events of active sleep.

State-dependent GABAergic inhibition of sciatic nerve-evoked responses of dorsal spinocerebellar tract neurons.

The recent discovery of a barbiturate-sensitive "general anesthesia switch" mechanism localized in the rat brain stem mesopontine tegmental anesthesia area (MPTA) has challenged the current view of the nonspecific actions of general anesthetic agents in the CNS. In this study we provide electrophysiological evidence that the antinociception, which accompanies the behavioral state resembling general anesthesia following pentobarbital (PB) microinjections into the MPTA of awake rats, could be accompanied by the attenuation of sensory transmission through the spinothalamic tract (STT). Following bilateral microinjections of PB into the MPTA spontaneous firing rate (SFR), antidromic firing index (FI), and sciatic (Sc) as well as sural (Su) nerve-evoked responses (ER) of identified lumbar STT neurons in the isoflurane-anesthetized rat were quantified using extracellular recording techniques. Microinjections of PB into the MPTA significantly suppressed the SFR (47%), magnitudes of Sc- (26%) and Su-ER (36%), and FI (41%) of STT neurons. Microinjections of PB-free vehicle control did not alter any of the above-cited electrophysiological parameters. The results from this study suggest that antinociception, which occurs during the anesthesia-like state following PB microinjections into the MPTA, may be due, in part, to (in)direct inhibition of STT neurons via switching mechanism(s) located in the MPTA. This study provides a provenance for investigating electrophysiologically the actions on STT neurons of other current agents used clinically to maintain the state of general anesthesia.

Article	Year
Transmission through the dorsal spinocerebellar and spinoreticular tracts: wakefulness versus thiopental anesthesia. Anesthesiology\| PubMed ID: 12411804	2002
State-dependent GABAergic inhibition of sciatic nerve-evoked responses of dorsal spinocerebellar tract neurons. Journal of neurophysiology\| PubMed ID: 15102903	2004
Network actions of pentobarbital in the rat mesopontine tegmentum on sensory inflow through the spinothalamic tract. Journal of neurophysiology\| PubMed ID: 19458144	2009

Shelly McErlane

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