Efferent discharges in alpha and fusimotor fibres of intercostal nerves of the cat

Respiratory mechanical advantage of the canine external and internal intercostal muscles

“…The main implication of the present studies, therefore, is that the actions of the external and internal intercostals on the lung during breathing are largely determined by the topographic distribution of neural drive among the muscles. A number of electrical recordings from intercostal muscles and nerves in anaesthetized cats (Sears, 1964;Bainton et al 1978;Kirkwood et al 1982Kirkwood et al , 1984Greer & Martin, 1990) and dogs (De Troyer & Ninane, 1986) have shown that the external intercostals are active during inspiration. The muscles also appeared to display greater inspiratory activity in the dorsal than in the ventral portion of the rib cage and greater inspiratory activity in the rostral than in the caudal segments.…”

Variations in the time course of the synchronization of intercostal motoneurones in the cat

“…In the analyses of this paper all the a-discharges of one filament were taken as a single population of spikes. a-and y-spikes were separated on the basis of spike height according to the criteria of Sears (1964a). In some of the later experiments, data were analysed to give the same type of cross-correlation histograms but by the use of a different computer, a PDP 11/34, and programmes written by Mr J. Davies.…”

“…In other instances the aim of the experiment was to maintain the animal specifically lightly anaesthetized and then to give a supplement either of the same size as our usual supplement (3 mg/kg) or larger. A lightly anaesthetized animal was one where there was a moderate but unsustained withdrawal of the forelimb to a strong pinch, but no reflex in the hind limb to a similar stimulus (Sears, 1964a;cf. Petersen, 1952).…”

“…However, we have no evidence to suggest that there are heterogenous groups of motoneurone represented in a filament. Although under different anaesthetic conditions different regions of the thorax may be recruited in different orders, the recruitment order of a-motoneurones within a given filament recording appears to be relatively constant (see illustrations in Sears, 1963Sears, , 1964a. For instance, during a breath or as CO2 increases or as anaesthesia changes the a-spikes in a filament recording are usually recruited in the order small spikes first, then larger spikes.…”

Target-dependence of sensory neurons: An ultrastructural comparison of axotomised dorsal root ganglion neurons with allowed or denied reinnervation of peripheral targets

“…The left side of the lower trace shows the restored inspiratory-phased activity recorded through a pair of small ball electrodes on the surface of the external intercostal muscle, and this local activity greatly diminished and came later in the breath when the electrodes were moved distally along the same segment. This pattern would be expected from the normal topographically distributed pattern of rib-cage inspiratory activity in eupnoea (Sears, 1964, Sears andStagg, 1976).…”