| Abstrakt: |
1. In pentobarbital-anesthetized cats, the discharge patterns of individual hindlimb muscle spindles (of M. triceps surae) were studied after i.v. administration of succinylbischoline (SCh; 0.25-0.5 mg/kg) and of the bischoline ether of hydrochinone ('M 110', Oesterreichische Stickstoffwerke, Linz; 2-5 mg/kg), respectively. 2. Both depolarizing substances were found to exert principally similar excitatory effects on the muscle spindles, differing only in the degree and the duration of their action, and in the doses needed. After M 110, the steady increase in afferent spindle discharges did not reach the peak frequencies observed after SCh, but lasted for more than 60 min, as compared to about 10 min after SCh. 3. Comparable differences existed in the time courses of neuromuscular blockade of the extrafusal muscle fibres. However, in contrast to SCh, M 110 was frequently found to induce incomplete abolition of intrafusal neuromuscular transmission. No signs of intrafusal twitches or fibrillations were observed in the spindle behavior. The stretch sensitivity of the receptor endings remained intact after both SCh and M 110. 4. With both substances, the monosynaptic mass reflex (MMR), recorded from the central stump of an appropriate ventral root, was abolished or depressed consequent to the high-frequency spindle discharges. Only with M 110, this depression was preceded by an initial phase of reflex enhancement; the subsequent reflex depression was less marked and of longer duration than that following SCh. 5. The prolonged spindle-exciting and reflex-depressing effects of M 110 beside its general muscle-relaxing action, might be useful for clinical therapeutical purposes. [ABSTRACT FROM AUTHOR] |
