ON THE SPINO-BULBO-SPINAL REFLEX IN DOGS, MONKEYS AND MAN

抄録

1. Experiments were carried out on 12 dogs (5-8 kg body weight) and 4 monkeys (2.3-3.2 kg) under chloralose anesthesia, and on 14 normal human subjects, in order to extend knowledge of the spino-bulbo-spinal (SBS) reflex.
2. In dogs and monkeys, stimulation of the spinal dorsal root yielded two types of reflex responses in the ventral root of the same segment. One of which was well-known mono- and poly-synaptic reflex responses with relatively short latencies and the other was a delayed reflex response with long latency.
3. The delayed reflex responses at the L₇ level in dogs and at the L₅ level in monkeys were respectively 30-35 msec. and 30-35 msec. in latency, 10-20 msec. and 10-20 msec. in duration, and 30-60μV and 40-90μV in amplitude.
4. When stimulus was applied to the afferent nerve in the hindlimb, two contrasting latency patterns were observed from spinal motor nerves at different segments, lumbar, thoracic and cervical. One of which was propriospinal reflex, the latency being increased as the recording points ascend the cord. The other was delayed reflex which decreased in latency as the recording points ascend the cord.
5. The delayed reflex response was evoked mainly with cutaneous nerve stimulation, and it was obtained only from nerves innervating flexor muscles.
6. When decerebration was made at the intercollicular level, the delayed reflex response was decreased in amplitude. In contrast, spinal transection at the C₁ level eliminated it completely.
7. Asphyxia and Nembutal anesthesia affected the delayed reflex response intensively and eliminated them much easier than the segmental polysynaptic reflex.
8. Averaged values determined in 3 dogs and 3 monkeys indicate effective spinal transmission velocities of 60±6 m/sec. in dogs and 61±6 m/sec. in monkeys for the ascending projections underlying the delayed reflex response, and 30±4 m/sec. in dogs and 28±4 m/sec. in monkeys for the descending projection of the delayed reflex response.
The above noted characteristics of the delayed reflex response in dogs and monkeys are almost the same as those of the SBS reflex response obtained in cats (SHIMAMURA & LIVINGSTON 1963). Therefore, it is reasonable to suppose that such a delayed reflex response may be the SBS reflex response in dogs and monkeys, although detailed analysis of the localization of the reflex center in the medulla oblongata has not been made in the present experiments.
9. In man, stimulation of the tibial nerve yielded a delayed reflex response with a latency of 70-80 msec. in the tibialis anterior muscle especially under light voluntary contraction of the muscle. This delayed reflex response was supposed to be due to the mechanisms of spino-bulbo-spinal reflex in man, judging from the fact that theoretically calculated latencies were coincident with those obtained in the present experiment.