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C von Euler

Publications and source records attributed to C von Euler.

At least 55 records · Page 3Linked to original sources
PubMed1976

Temperature effects on the inflation reflex during expiratory time in the cat.

In order to obtain further information on the mechanisms controlling expiratory duration (TE) we have studied the effects of changes in body temperature on reflex characteristics of the TE-prolonging inflation reflex. In cats under light pentobarbitone anesthesia controlled volume changes were applied at various times in expiration and the changes in TE were measured from records of phrenic activity. Inflations falling in the last 20% of the control expiratory time were without effect. This reflex insensitive phase remained a constant fraction of expiratory time when respiratory rate was changed with temperature. The relative reflex responsiveness increased, and the volume threshold was reduced with increasing respiratory rate. The inflation reflex characteristics showed integration of the incoming pulmonary stretch receptor activity. The integrating mechanism exhibited a "leaky" character, the decay rate of which changed with body temperature. Functionally the duration of the inspiration-inhibiting activity controlling expiratory duration can be regarded as dependent on 3 main factors 1) the initial peak level of the inhibitory activity, 2) the amount and timing of the vagal afferent activity which adds to this inhibition, and 3) its rate of decay. The results suggest that all these factors are influenced by changes in temperature.

Animals↗
PubMed1976

Excitability changes of the inspiratory "off-switch" mechanism tested by electrical stimulation in nucleus parabrachialis in the cat.

The time course of the excitability of the inspiratory "off-switch" mechanism with and without phasic vagal stretch receptor feedback has been studied in cats under light pentobarbitone anesthesia by electrical stimulation in the rostral pons using brief tetanic stimulation (300 Hz for 0.2 s). The threshold strength required just to elicit inspiratory "off-switch" was high early in inspiration and fell steeply with time. The threshold curves were steeper with than without phasic vagal feedback, and the difference reflects the phasic vagal contribution to the excitability of the inspiratory "off-switch" the absence of phasic vagal vagal feedback the time course of this threshold curve usually corresponded closely to that of the "integrated" phrenic activity at all PCO2 levels and body temperatures tested indicating that the "integrated" phrenic activity can be used as an index of the centrally generated inspiratory activity. In response to a rise in PCO2 both the rate of change of excitability of the inspiratory "off-switch" mechanism and its initial threshold level was increased. Changes in body temperature caused no change in the initial threshold but produced marked changes in the rate of rise of the "off-switch" excitability; Following an "augmented breath" the inspiratory "off-switch" threshold was markedly reduced

Animals↗
PubMed1973

The role of proprioceptive afferents in the control of respiratory muscles.

Building largely on the results of previous studies of motor control in respiration the role of proprioceptive control of respiratory movements is discussed with particular reference to the significance of the following points: (i) The co-activation of fusimotor and alpha motoneurons in load compensation and in the control of velocity and force of the respiratory movements. (ii) The convergence onto the same intercostal spindle of fusimotor fibres for respiratory movements and for postural activity. (iii) The difference between proprioceptive control of intercostal muscles on the one hand and the diaphragm on the other, and of the control of the phrenic motoneuron pool exerted by intercostal proprioceptors. (iv) The cerebellar control both of the fusimotor-alpha balance between the indirect drive of the intercostal motoneurons and of the responsiveness of the phrenic motoneuron pool to respiratory and reflex influences. (v) Results suggesting spinobulbar reflex effects on the control of rate and depth of respiration from muscle and joint receptors of the thoracic wall.

Cerebellum↗
PubMed1972

On the regulation of depth and rate of breathing.

1. The relationships between the depth of a breath and the durations of the inspiratory and expiratory phases have been studied in cat and in man during rebreathing, and in cat using artificial inflations of different magnitudes and timings.2. In the cat, the apparent volume threshold for termination of inspiration (Hering-Breuer threshold) decreased with time from the onset of the inspiratory phase.3. Both in rebreathing experiments and with artificially imposed inflations in the cat, the inspiratory duration T(I) was dependent upon tidal volume V(T), and this dependence could be expressed by a hyperbolic relationship of the form (V(T)-V(0)) T(I) = C where V(0) and C are constants.4. The time course of this ;Hering-Breuer' threshold was dependent on intact vagus nerves. After vagotomy the inspiratory duration remained essentially constant with changes in tidal volume produced either by artificial inflation or by the increased respiratory drive due to accumulation of CO(2) during rebreathing.5. In man during rebreathing, the relation between volume and inspiratory duration typically showed two different characteristics. 1, at tidal volumes up to 1.5-2 times eupnoeic values, inspiratory duration did not change as tidal volume increased in response to increased P(CO2). This range of operation has been designated range 1. 2, as tidal volume increased above this range 1 a second range designated range 2 was observed where inspiratory duration was volume dependent in the same manner as in the cat.6. In cat under pentobarbitone anaesthesia, a range 1 operation was not seen except after vagotomy. However, under urethane anaesthesia a range 1 plus a range 2 operation could be seen.7. The differences between cat and man appeared to be largely quantitative rather than qualitative.8. In both cat and man, expiratory duration was dependent on inspiratory duration, usually with a linear relationship.9. The experimental results were assembled in the form of an inspiratory characteristic and a timing relationship that serve as a model of the respiratory mechanisms controlling the depth and rate of breathing. The model predicts that the depth and duration of a breath are related in a definite manner fixed by the system characteristics and that ventilation is adjusted by setting the appropriate operating point on these characteristics. The operating point is determined primarily by how quickly lung volume increases, i.e. the rate of increase of inspiratory motor activity.

Adult↗
PubMed1966

Reflex and cerebellar influences on alpha and on 'rhythmic' and 'tonic' gamma activity in the intercostal muscle.

1. Efferent intercostal alpha and gamma activity and afferent intercostal muscle spindle activity were studied in decerebrate cats in response to stimulation of the anterior lobe of the cerebellum and to postural and other reflexes.2. Low threshold intercostal responses were elicited from lobuli IV and V of the anterior lobe of the cerebellum.3. The existence of two functionally different types of intercostal gamma neurones has been confirmed. These are the ;rhythmic' or ;specifically respiratory' gamma neurones, and the ;tonic' gamma neurones.4. In response to cerebellar stimulation, facilitatory, inhibitory and diphasic tetanic and post-tetanic effects were obtained from alpha and the two types of gamma fibres in both external and internal intercostal nerve branches.5. Generally both inspiratory and expiratory alpha and gamma activity was facilitated in response to tetanic stimulation at contralateral stimulus sites, and inhibited in response to stimulation of ipsilateral sites.6. ;Rhythmic' gamma activity appeared to be rather closely linked to the respiratory alpha activity but the balance between ;rhythmic' gamma and alpha was often changed in response to cerebellar stimulation, as indicated by the responses of primary muscle spindle afferents.7. The ;tonic' gamma neurones were as a rule more responsive to cerebellar stimulation than were the alpha and ;rhythmic' gamma neurones. Long-lasting post-tetanic effects were much more prominent in the ;tonic' gamma fibres than in the alpha or ;rhythmic' gamma fibres.8. ;Rhythmic' gamma activity was abolished after cervical transections of the cord. ;Tonic' gamma activity remained in the spinal preparations although usually at a different discharge rate.9. ;Tonic' gamma neurones were more responsive than the ;rhythmic' gamma neurones to the proprioceptive gamma reflex elicited by passive movements of the chest wall as well as to other spinal and supraspinal reflexes.10. Both ;dynamic' and ;static' gamma fibres seem to be represented in the group of ;tonic' intercostal gamma neurones.11. The significance of the results are discussed with regard to the following two main points: (a) integration of respiratory and postural functions of the intercostal muscles; (b) cerebellar control of the alpha-gamma balance in active contractions and passive relaxations.

Animals↗
PubMed1966

Dynamic and static contributions to the rhythmic y activation of primary and secondary spindle endings in external intercostal muscle.

1. In cats anaesthetized with sodium pentobarbital 160 external intercostal muscle spindle afferents were identified by their pause in response to ventral root stimulation; the internal intercostal muscle was denervated. 2. In order to assignate the afferents to either primary or secondary endings they were tested for their responsiveness to vibration (Bianconi & Van Der Meulen, 1963). The maximal frequency which they were able to follow regularly for at least four cycles, termed 'critical frequency', was determined. 3. The endings fell into two groups: low-f (frequency) sensitive endings with critical frequencies below 400 c/s and high-f sensitive endings with critical frequencies above 400 c/s. The latter were regarded as primary endings and the former as secondary ones. 4. The manner in which the spindle endings resumed activity after a pause produced by shocks to the ventral root, i.e. whether 'phasic' or 'tonic' (Granit & Van Der Meulen, 1962) was studied in all the spindle afferents. 5. All the secondary (low-f sensitive) endings were 'tonic' except three for which the determination of critical frequency was questionable. Both 'tonic' and 'phasic' properties were found among the primary (high-f sensitive) endings. 6. The majority of the secondary endings (74%) showed inspiratory ythmic fusimotor activation in parallel with the skeletomotor contracton as did the primary endings (79 %). 7. Fifty-seven spindle endings which all showed marked rhythmic inspiratory gamma activation were tested for respiratory variations in their dynamic responses to steady stretch and length changes introduced at low repetition rates. 8. The results indicate that both 'dynamic' and 'static' gamma fibres are represented among the rhythmic gamma fibres controlling primary muscle spindle endings, whereas rhythmic activation of secondary endings seems to be mediated only by 'static' fibres.

Animals↗