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M Andrzejewski

Publications and source records attributed to M Andrzejewski.

6 recordsLinked to original sources
PubMed2004

Rhythms, synchrony and electrical coupling in the Locus coeruleus.

Electrical coupling of neurones is believed to promote synchronized activity. It may, however, also be a requirement for the maintenance of endogenous rhythmic activity in some systems. In en bloc isolated brainstem-spinal cord of the neonatal rat simultaneous whole cell recordings from pairs of LC neurones (n = 47 pairs) disclosed for the most part strongly synchronized activity which could take the form of tonic spiking or phasic bursts. Simultaneous whole cell recording from LC neurones and glia also revealed synchronized waves of depolarization in 7 of 17 pairs. This synchrony was partly due to respiratory-phased synaptic input and partly due to mechanisms, which were not dependent on chemical synapses. The gap junction uncoupler carbenoxolone suppressed non-synaptic rhythmic activity in LC neurones, but did not suppress either respiratory-phased synaptic input to these neurones or their excitatory response to increased CO(2). We give preliminary direct evidence for the existence of a current pathway between LC neurones, which is inhibited by carbenoxolone. Within the LC nucleus carbenoxolone-sensitive electrical coupling, which may involve neurone-glia as well as neurone-neurone interactions, may be required not just for synchronization, but also for the maintenance of rhythm.

Action Potentials↗
PubMed2004

[Influence of prion protein gene polymorphisms on performance traits in German meat sheep breeds].

PrP polymorphisms influence the scrapie susceptiblility of sheep. The objective of this study was to analyse the association between performance traits and the PrP genotype in the sheep breeds German black-headed and German white-headed mutton, Bleu du Maine, German mutton merino, Leine, Texel and Suffolk from Lower Saxony and Westphalia. We analysed performance traits such as scores for muscle mass, type and wool quality and the calculated daily weight gain using linear animal models. In all seven breeds no statistically significant associations were found between performance traits and the occurrence of ARR alleles, and the ARR/ARR genotypes, respectively. All genotyped sheep of all breeds investigated showed significantly superior performance traits in comparison to the non-genotyped animals.

Animals↗
PubMed2001

Synchronized rhythms in chemosensitive neurons of the locus coeruleus in the absence of chemical synaptic transmission.

The activity of locus coeruleus (LC) neurons was examined in the en bloc isolated brainstem-spinal cord of the neonatal rat using paired whole cell or whole cell plus extracellular recording. In artificial cerebrospinal fluid (ACSF) LC neurons were synchronized by their respiratory innervation and in some neurons showing tonic or burst patterns of discharge these patterns of discharge could also be synchronized. Replacing ACSF with low Ca(2+)-high Mg(2+) generated synchronized rhythmic bursts which remained synchronized at high CO(2) (up to 20%). This rhythm was suppressed by TTX. Substitution of Ba(2+) for Ca(2+) in ACSF generated a synchronized rhythm which was TTX-insensitive. The frequency of this rhythm increased by 31+/-16% on raising CO(2) concentration from 2 to 10%. We conclude that the capacity of chemosensitive LC neurons to generate a synchronized rhythm depends on their electrical coupling, but not on chemical synaptic transmission.

Animals↗
PubMed1999

Locus coeruleus neurones in vitro: pH-sensitive oscillations of membrane potential in an electrically coupled network.

The response to hypercapnic acidosis (2-8% CO2, bath pH 7.8-7.2) was examined in whole cell recordings from neonatal (P1 to P5) rat Locus coeruleus (LC) neurones in the in vitro brainstem-spinal cord preparation exposed to low Ca2+ (0.2 mM)-high Mg2+ (5 mM). This medium suppressed chemical synaptic transmission and resulted in a pattern of subthreshold oscillations of membrane potential and rhythmic burst discharge which was synchronized throughout the network. The oscillation was suppressed, and the discharge of individual neurones desynchronized, by the gap junction uncoupler, carbenoxolone, indicating that in low Ca2+-high Mg2+ LC neurones form an electrically coupled network. Switching from 2 to 8% CO2 decreased the oscillation amplitude and increased its frequency. The oscillation was suppressed by external Cd2+ and by TTX. but persisted during injection into the cell soma of QX-314. We conclude that in LC neurones acidosis increases the frequency of a Ca2+- and Na+-dependent dendritic oscillator which is synchronized by gap junction coupling throughout the network. This coupling is retained during acidosis.

Acidosis↗