The Action of Adrenaline and Nor-Adrenaline on the Knee-Jerk

Abstract

1. The influence of intravenously administered adrenaline and nor-adrenaline on the knee-jerk of anaesthetized cats was studied by recording the contraction amplitude of the quadriceps femoris muscle. 2. In most cases a primary increase of the amplitude was observed followed either by a decrease to the original amplitude or by a stronger decrease and a gradual restoration of the amplitude. Doses of pressor amine of 2–100 μg./kg. caused this phenomenon. 3. The primary increase might be caused by an excitatory influence of the hormones on the spinal centers and on the muscle. 4. In a few occasions a primary decrease was recorded followed by a restoration of the original amplitnde. This effect only occurred with doses > 20–30 μg. /kp. and might be caused by a decreased blood flow through the muscle or by hypertonicity of the thigh muscles. 5. The primary increase did not entirely disappear upon administration of dihydro-ergot amine in a dosage which reversed the blood pressure effect as caused by catechol amine injection. 6. Transection of the thoracic spinal cord did not change the action of adrenaline and nor-adrenaline on the knee-jerk. 7. The apnoea resulting from adrenaline or nor-adrenaline administration did not cause the phenomena described.