The effects of single afferent impulses on the probability of firing of external intercostal motoneurones in the cat

摘要: 1. Recordings of afferent discharges from external intercostal muscle spindles were made in-continuity dorsal roots anaesthetized, paralysed cats and the afferents characterized as described in preceding paper (Kirkwood & Sears, 1982). 2. The strengths time courses raised probabilities firing motoneurones evoked by synaptic actions impulses measured constructing cross-correlation histograms individual motoneurones, which simultaneously recorded cut central ends nerve filaments. Other roots, apart rootlet containing fibre, to prevent synchronization affecting results. 3. Cross-correlation involving single efferent showed narrow peaks (mean half-width 0·99 msec) at monosynaptic latencies. 4. This mean is slightly longer than rise-time e.p.s.p.s paper, but much shorter those e.p.s.p.s. These measurements, together with shapes histogram thus confirm prediction Kirkwood Sears (1978) that shape such a peak should be approximated differential underlying e.p.s.p. plus course itself. Amplitudes also consistent predictions (1978). 5. multi-unit entirely used demonstrate patterns projections different groups motoneurones. 6. Individual excited α all spike sizes filament recordings excitation γ was not detected. 7. same segment both adjacent segments, no projection beyond these detected. 8. amplitude taken measure over-all strength connexions given segment. When this for afferent, sixteen out nineteen there highly significant positive correlation conduction velocity afferent. remaining three gave connexion appeared stronger would expected rest population afferents. 9. segments generally lower