Respiratory and circulatory effects of 100 meq-l potassium or 2 per cent procaine in the cerebrospinal fluid of cats.

Abstract

In cats lightly anesthetized with chloralose-urethane, the ventral surface of the medulla was perfused with mock CSF of different potassium concentrations, or with solutions containing 2% procaine. In some experiments a wall of gelatin foam glued onto the midline of the medulla allowed a separate perfusion of either half of the medullary surface. To study the blockade of different layers of the medullary tissue, electrical stimuli were applied at varying depths from the ventral surface, at a spot located medially from the roots of the hypoglossal nerve and 3 mm laterally from the midline. 1. Both potassium at 100 meq/l, and 2% procaine, cause respiratory arrest after 50–650 sec when perfused over the ventral medullary surface. 2. Perfusion of one half of the ventral medullary surface with potassium at 100 meq/l, the opposite half being perfused simultaneously with reference solution, causes a decrease in ventilation of more than 50% and in some cases respiratory arrest. 3. Electrical stimuli (1 V; 60 sec−1) 200 μ below the surface cause a slight inspiratory displacement of the respiratory leve, and later an increase in tidal volume and frequency. When the medullary surface is perfused either with the solution of high potassium concentration, or with 2% procaine, the response to these stimuli disappears at about the time of respiratory arrest. 4. The response to electrical stimuli (0.5 V; 60 sec−1) applied 1.5 mm below the surface — a vigorous inspiration followed by apneusis in extreme inspiratory position — outlasts for several minutes the respiratory arrest induced by perfusion with 100 meq/l potassium. 5. Potassium at 100 meq/l causes a transitory fall in blood pressure; later the blood pressure rises above the control level During perfusion with 2% procaine, the blood pressure usually decreases and remains on this low level until the drug is washed out.