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Biomedical subjects

V Růzicka

Publications and source records attributed to V Růzicka.

25 records · Page 2Linked to original sources
PubMed1985

How far from the stimulation site in myenteric plexus-longitudinal muscle preparations the neurogenic cholinergic contraction can be evoked?

Neurogenic contractions of a segment of myenteric plexus-longitudinal muscle strip preparations from the guinea-pig ileum were evoked. The site of electric stimulation was separated from the contracting segment by a gap preventing the spread of muscle action potentials set up in other regions. The width of the separating gap (2-20 mm) indicated the length of nerve fibers that could conduct impulses across and trigger cholinergic contractions behind the gap; it was more than 12 and less than 16 mm. Transmission of excitation was more effective in the aboral direction compared to the oral direction and was not apparently affected by noradrenaline nor by substance P.

Animals↗
PubMed1984

Possible role of prostaglandins in post-tetanic potentiation at the nerve-muscle junction in the longitudinal muscle strip of guinea-pig ileum.

The effect of tetanic stimulation on the twitch responses of the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum to electrical stimulation was investigated in the presence of naloxone. Under this condition, or after the addition of PGE2, twitch contractions were maximal and no potentiation of twitches following tetanus was observed. In the presence of indomethacin (1 mumol litre-1) twitches were diminished and post-tetanic potentiation (PTP) was manifested. PTP was seen with indomethacin concentrations of 1 to 20 mumol litre-1 or after simultaneous addition of diphloretin phosphate (16 mumol litre-1). Thus it seems unlikely that the effect of prostaglandins released during tetanic stimulation would be of key importance for the manifestation of PTP. Rather it is thought that a decrease in the release of acetylcholine from motor nerve terminals, and consequently smaller twitches in the presence of indomethacin, offer favourable conditions for PTP.

Acetylcholine↗
PubMed1984

Smooth muscle stimulation by an immunomodulatory compound muramyl dipeptide: does it involve serotoninergic system?

Contractions evoked by muramyl dipeptide (MDP), a synthetic compound possessing immunostimulatory properties, were studied in several isolated nerve-smooth muscle preparations. The contractions by micromolar concentrations of MDP were evoked either by direct interaction with smooth muscle (rat stomach strip) or at least partly indirectly via neurogenic stimulation (guinea pig ileum); the effect was stereospecific since the MDP-D was not active. The insensitivity of the preparations to serotonin (5-HT), either inherent (vas deferens) or after 5-HT antagonists or after desensitization to 5-HT, prevented or markedly reduced the contractile activity by MDP. On the other hand, a nanomolar concentration of MDP enhanced the sensitivity of the rat stomach strip to 5-HT.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1983

Posttetanic potentiation at the neuromuscular junction of the guinea-pig ileum longitudinal muscle strip: influence of calcium, temperature, ouabain and hexamethonium.

The effect of tetanic stimulation on the twitch responses of the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum was investigated. In the presence of naloxone plus indomethacin twitch contractions following tetanus were potentiated. This posttetanic potentiation (PTP) of twitches was absent after reducing calcium concentration (0.6 mmol/l) in the bath or lowering bath temperature (22 degrees C); doubling calcium concentration (5 mmol/l) enhanced PTP. The addition of ouabain (0.8-5 mumol/l) prevented PTP; following the washout of ouabain the time course of PTP was prolonged. Hexamethonium (0.5 mmol/l) did not prevent PTP. The results suggest that similarly to the situation at nicotinic synapses of the striated muscle the mechanism of PTP at this muscarinic synapse might be associated with changes in calcium distribution. Moreover, the effect of ouabain might suggest the importance of electrogenic sodium pumping from and hyperpolarization of cholinergic nerve terminals after tetanus.

Animals↗