Abstract
1. Experiments were carried out on 25 adult cats under spinal transection at the C1 level in order to extend observations on the chloralose jerky muscular contraction and to analyze the effects of chloralose on spinal reflexes.
2. Chloralose (25-35mg/kg) was administered intravenously to spinal cats. These cats did not exhibit generalized jerky muscular reactions, even when a large dosage of 100mg/kg was administered.Blood pressure and heart rate were not changed by chloralose anesthesia at a dosage level lower than 45mg/kg. The following results were observed: 1) Slight augmentation of the monosynaptic reflex response, with a reduction in amplitude of polysynaptic reflex responses. 2) Reduction of the inhibitory influence of the sural nerve on the extensor monosynaptic reflex response. 3) Reduction of the Renshaw cell recurrent inhibition to the motoneurons. 4) Reduction of potential from the cord dorsum (N2 and P), dorsal root, and dorsal root reflex responses. 5) Reduction of augmentation of antidromic potentials of the primary afferent fibers following sural nerves timulation. 6) Reduction of the interlimb reflex response and augmentation of the local lumbosacral monosynaptic reflex response to the forelimb nerve stimulation, without alteration of the initial diminution.
3. The observations suggest that the chloralose has a depressing action on the spinal polysynaptic reflex process and/or interneurons. Neural mechanisms of the chloralose jerky muscular contraction could not be due to mechanisms in the spinal cord.
