Actions of morphine on the segmental reflex of the decerebrate-spinal cat.

1. The actions of morphine were studied on the segmental reflex of the decerebrate-spinal cat. Morphine decreased arterial blood pressure.2. Morphine inhibited mono- and polysynaptic reflexes. The influence of morphine on monosynaptic reflexes was more obvious at stimulation of the dorsal root at a frequency of 12.5 Hz than at 0.5 or 2.5 Hz.3. The total amount of activity recorded from the ventral root after morphine depended on whether or not the evoked reflex was maximal or submaximal.4. These actions of morphine were antagonized by naloxone.