The effect of various ventilation conditions on evoked potentials of the visual cortex of the cat in distention of the stomach

: In 10 cats anaesthetized using chloralose and with muscular relaxation by gallamine and continuous artificial ventilation in acute experiments photically evoked potentials (PEP) were recorded from the visual area of the cortex under different intragastric pressures and varying tidal volumes. It was the aim of this study to examine whether an exteroceptive stimulus (light flash) in the visual analyzer, which is influenced by an interoceptive stimulation (gastric pressure), may also be modified by different tidal volumes. Times, amplitudes and slope parameters, blood pressure and heart rate of the animals were studied. The PEP of the visual cortex was modified under the influence of the interoceptive stimuli. It could, however, be shown that already hypo- and hyperventilation alone may cause alterations in the latency period of the PEP. They arise in a different manner in individual parts of the measured parameters of the PEP and do not change these values in a typical manner. Additional dilatation of the stomach may suppress the phenomena caused by alterations in the tidal volume. Thus, attention should be paid to both blood gases and acid base balance in animals in studies on viscero-cerebral interrelationships as well as to interactions between different analyses using the method of evoked potentials.