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Biomedical subjects

P Langhorst

Publications and source records attributed to P Langhorst.

33 records · Page 2Linked to original sources
PubMed1977

Neuronal activity with cardiac rhythm in the nucleus of the solitary tract in cats and dogs. I. Different discharge patterns related to the cardiac cycle.

In anaesthetized, spontaneously breathing cats and dogs, extracellular recordings were made of the spontaneous activities of 28 single neurones with cardiac rhythm. It was confirmed by histological examination that the neurones were situated in the mediodorsal portion of the nucleus of the solitary tract. Different discharge patterns in relation to the heart cycle were demonstrated using R-deflection triggered histograms. Most of the neurones discharged with systolic bursts. In the cat, about half the neurones showed two to three activity peaks in the histograms which could occur at any time of the heart cycle. The height of the various peaks sometimes changed in different ways in the course of the respiratory cycle. It can be concluded that different cardiovascular afferents converge to single neurones. In some neurones it could be shown by elimination of the vagus nerves that the pulse-rhythmical discharge pattern was induced mainly by vagal inputs, mainly by glossopharyngeal inputs or by inputs from both nerves. Two-thirds of the neurones discharging with systolic bursts could be enhanced by increasing the arterial blood pressure. In some of these neurones a proportionality between the number of impulses per heart cycle and the mean arterial blood pressure was found.

Action Potentials↗
PubMed1977

Neuronal activity with cardiac rhythm in the nucleus of the solitary tract in cats and dogs. II. Activity modulation in relation to the respiratory cycle.

In anaesthetized, spontaneously breathing cats and dogs extracellular recordings were made of the spontaneous activities of 28 single neurones with cardiac rhythm. Histological exmaination confirmed that the neurones were situated in the mediodorsal portion of the nucleus of the solitary tract. The neurones, which had already been analysed in respect to their pulse-rhythmical pattern27, were investigated by means of inspiration triggered histograms. The neurones could be grouped according to the respiratory modulations of their activities. Increased activities occurred during (a) the rise of the respiratory blood pressure wave, (b) the respiratory rest period, and (c) the inspiration. Three neurones did not exhibit respiratory modulation. The respiratory modulations of groups a and b were most probably caused by changing inputs from cardiovascular receptors in the course of respiration. It could be shown by adequate stimulation and elimination of the vagus nerves that the neurones of group c were influenced by lung inflation receptors as well as by cardiovascular receptors.

Action Potentials↗
PubMed1977

Nucleus of the solitary tract and the J reflex.

Experiments were carried out on cats anaesthetized with chloralose-urethane with a view to defining certain central pathways for the J reflex elicited by the right atrial injection of phenyldiguanide. The resulting motor inhibition was manifested by reduction in the amplitude of the knee jerk. The dorsal surface of the medulla was exposed and free riding platinum quartz electrodes were introduced into the nucleus of solitary tract. Lesions were made in the NTS by passing current of know intensity through the electrodes. The J reflex was abolished by bilateral lesions in the NTS. It was concluded that the nucleus of solitary tractisan essential part of the central pathway of the J reflex.

Animals↗
PubMed1976

Neuronal activity with relation to cardiac rhythm in the lower brain stem of the dog.

Extracellular recordings of reticular neurons in the lower brain stem were performed in anesthetized dogs. Thirty out of 131 neurons showed rhythms of about 2-4 c/sec which were similar to heart or to EEG rhythms. By means of post-event-time histograms, correlations to the EEG delta-theta rhythm could be found in some neurons. These results were published elsewhere. Fixed relations of the neuronal activity to the cardiac rhythm could be verified in 7 neurons. Two neurons showed maxima 70 msec and 120 msec, respectively, after the beginning of the pulse wave. Two neurons showed minima after 110 msec and 130 msec, respectively. Three pulse-rhythmical neurons could not be classified in this way. This rhythmicity was changing or vanishing during the course of registration, but it could be strengthened experimentally by blood-pressure increase. It was shown that these neurons receive inputs from cardiovascular afferents and therefore are blood-pressure dependent neurons. From the finding that pulse-rhythmical modulation is different at different times under the same blood-pressure levels, it is assumed that there are varying strong influences from other systems to these neurons. The fact that these neurons are influenced by cardiovascular afferents does not mean, however, that they are cardiovascular neurons exclusively. It is suggested that blood-pressure reticular neurons may belong to the cardiovascular system as well as to other brain stem systems.

Animals↗
PubMedDate not supplied

Discharge pattern of neurons in the nucleus tractus solitarii (NTS): its cardiac rhythm is modulated by firing rate of the neurons.

In the nucleus tractus solitarii (NTS) neurons discharge in relation to cardiac rhythm. This cardiac rhythm exhibits various patterns designated as CRDPs (cardiac rhythmic discharge patterns). The CRDPs are estimated by post-event-time histograms (PETH) triggered by the R-waves of the ECG. Modulations of CRDPs appear as changes in the number and height of peaks in the PETHs. The amount of basic activity, which is not related to the cardiac cycle, alters CRDP. PETHs constructed during various phases of respiration reveal modulations of CRDPs within the respiratory cycle. As our previous work indicated, the NTS neurons exhibit typical reticular rhythms. In this paper we also found that the basic activity of NTS neurons was often changed by other influences for which no comparable patterns could be observed in other simultaneously acquired signals. When we constructed PETHs according to the activity level of the NTS neurons, i.e., firing level per cardiac cycle, modulations of CRDPs which were even stronger than respiratory or reticular rhythmical modulations became clear. The modulations of CRDPs caused by different origins were found to be present in the same neuron interlaced in time. The possible role played by these modulations of CRDPs in the coordination of different functional systems in the organism is discussed.

Animals↗