Level of oxytocin release induced by vaginal dilatation (Ferguson reflex) and vagal stimulation (vago-pituitary reflex) in lactating rats (author's transl)]

1. Vaginal dilatation for 30 seconds caused a rapid and brief increase in intramammary pressure which was equivalent to that evoked by 160 muU of oxytocin (Syntocinon) injected intravenously. 2. The rise in mammary pressure induced by the stimulation of the central end of a severed vagus nerve for 30 seconds (5 V, 0,5 ms, 50 HZ) was similar to the response obtained with an intravenous injection of 360 muU of oxytocin. 3. The vago-pituitary reflex leads to the liberation of large amounts of antidiuretic hormone which does not interfere with the effect of oxytocin on the mammary gland, since dexamethasone phosphate prevented the vasopressor effect without significantly affecting the increase in intramammary pressure.     

Paradoxical vagal effects on the cardiac rhythm in cats

In anaesthetised cats, an increase in the vagal burst rate resulted in a paradoxical decrease of vagal bradycardia. This seems to be due to a shift of the vagal stimulus position towards early phase of cardiac cycle. The mechanism of this paradoxical effect depends on the magnitude of vagal chronotropic effect upon the time of vagal stimulus delivery within cardiac cycle.     

Modification of the Hoffmann reflex in function of athletic training (author's transl)]

The present study measures the values of the Hoffmann reflex and principally the relationship between the maximum reflex response and the maximum direct motor response (H max/M max) and their evolution. The subjects were athletes, performing aerobic and anaerobic type activities, divided into six groups (swimmers; soccer players; tennis players; sprinters; middle and long distance runners; and nonspecific athletes). The results show the average values of the H max/M max (53%) to be not different from those of nonathletes. When separated into aerobic and anaerobic groups, significant differences were found: the values are significantly inferior for subjects participating in anaerobic sports (37%) whereas we found an increase (from 55-75%) in the relationship for swimmers performing aerobic activities after 3 years of regular training. The results suggest, in accordance with previous authors, the possibility of a correlation between the modifications of the H max/M max and the type of activities (aerobic or anaerobic).     

Comparison of the effects of analgesia-producing peripheral and central stimulations in cats. Effect of nalorphine (author's transl)]

The effects of weak intensity percutaneous peripheral stimulations (SPPc) on the transmission of nociceptive messages induced by stimulation of the dental pulp have been studied on anaesthetized cats. 1. The jaw opening reflex (ROG) and the evoked potentials in the thalamic center median (CM), by stimulation of the dental pulp, disappear after a mean of 30 min after the start of SPPc. 2. These effects are analogous to those obtained by stimulation of the periaqueductal gray matter (St.GC) or by I.V. morphine injection. 3. The I.V. injection of the morphine antagonist (Nalorphine) blocks both the effects of the SPPc and those of the St.GC. 4. The authors put forth the hypothesis of a common mechanism of action of the SPPc and the St.GC which, through the liberation of endogenous morphinomimetic substances, would activate descending inhibitor impulses.     

Frequency-dependent effects of hypercapnia on respiratory mechanics of cats

The effect of increasing arterial partial pressure of CO2 (PaCO2) on respiratory mechanics was investigated in six anesthetized, paralyzed cats ventilated by constant-flow inflation. Respiratory mechanics were studied after end-inspiratory occlusions. Zero frequency resistance (Rmax), infinite frequency resistance (Rmin), and static elastance (Est) were calculated for the respiratory system, lung, and chest wall. Alveolar ventilation was manipulated by the addition of dead space to achieve a range of PaCO2 values of 29.3-87.3 mmHg. Cats did not become hypoxic during the experiment. Under control conditions marked frequency dependence in Rmax, Rmin, and Est of the respiratory system, lungs, and chest wall was demonstrated. The chest wall contributed 50% of the total resistance of the respiratory system. With increasing PaCO2 the only resistance observed to increase was Rmax of the lung (P less than 0.01). There were also no changes in the static elastic properties of either the lungs or the chest wall. These results suggest that hypercapnia increases resistance by changes in the lung periphery and not in the conducting airways.