The Journal of physiology
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The Journal of physiology · Sep 1977
Dorsal horn cells that respond to stimulation of distant dorsal roots.
Experiments were carried out to find if there were post-synaptic effects produced by impulses in the long ranging primary afferents, which had been shown by Wall & Werman (1976) to extend from upper lumbar dorsal roots to the sacral segments. Dorsal rootlets were stimulated in decerebrate low-spinal adult cats.1. The dorsal root potential and ventral root reflex were recorded on S1 root filaments, in response to stimulation of dorsal rootlets extending from L1 to S1. ⋯ It was established that some L4 cells respond to S1 dorsal root stimulation, just as the main study had shown that S1 responds to L4.7. It is concluded that substantial numbers of dorsal horn cells, including cells with many types of cutaneous receptive field, respond to two classes of synaptic in-put: one effective in firing the cell upon natural cutaneous stimulation, and one relatively ineffective, capable of driving the cell only when stimulated electrically and thus carrying a synchronous volley from a number of highly convergent axons. The contribution of this secondary afferent channel to normal and pathological cord physiology has now to be determined.
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The Journal of physiology · May 1977
Inactivation of the asymmetrical displacement current in giant axons of Loligo forbesi.
1. Asymmetrical displacement currents ('gating currents') have been recorded in intracellularly perfused squid giant axons by averaging the currents associated with depolarizing and hyperpolarizing pulses. The relation between 'gating current' and Na inactivation was studied by investigating the effect of pulse duration and conditioning pulses. 2. ⋯ Its size was reduced to 46-71% and 61-94%, respectively, for a recovery interval of 1-75 and 5 msec at 2-3 degrees C. The reduction of the Na current, measured under similar conditions, was more pronounced; the Na current was decreased to less than 50% of its normal value. 5. The observations about the effect of pulse duration and conditioning pulses on the 'gating current' are qualitatively consistent with those of Bezanilla & Armstrong (1974, 1975) and support the view that part of the asymmetrical charge displacement is inactivated during a 10-20 msec depolarization.
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The Journal of physiology · Dec 1976
The thermal sensitivity of the polymodal nociceptors in the monkey.
1. The static and dynamic sensitivities to thermal and mechanical stimuli of polymodal nociceptors in hairy skin of the anaesthetized monkey have been investigated by recording activity in their primary nerve fibres. 2. Polymodal nociceptors responded to skin pricking, pinching and heating to temperatures higher than 40 degrees C. ⋯ During the first series of stimulations, the threshold at which the individual polymodal nociceptors began to discharge to heat stimuli varied from 40 to 46.5 degrees C. The mean threshold of the population was 42.5 degrees C. 7. No change in the threshold was observed when responses to 0.2 and 1.5 degrees C/sec rates of heating were compared...
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The Journal of physiology · Nov 1976
Spontaneous subminature end-plate potentials in mouse diaphragm muscle: evidence for synchronous release.
1. Miniature end-plate potentials (min.e.p.p.s) were recorded from small muscle cells of mouse diaphragms. Min.e.p.p. amplitude histograms showed successive peaks which were integral multiples of the smallest peak. ⋯ Colchicine (5 X 10(-4)M) within minutes reduced the major mode min.e.p.p.s by half (mean of major peak reduced to sixth or seventh peak). Additional colchicine (10(-3)M reduced the major mode min.e.p.p. amplitude to a fifth of that of control (mean of major mode min.e.p.p.s at the third peak) with no change in position of the submin.e.p.p. peak. Min.e.p.p. amplitudes slowly recovered to half control values after washing. 7...
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The Journal of physiology · Jul 1976
Functional characteristics of lateral interactions between rods in the retina of the snapping turtle.
1. Intracellular recordings were made of the slow hyperpolarizing light responses of single rods in the retina of the snapping turtle. Physiological criteria used to identify rods were verified by intracellular injections of Procion Yellow. 2. ⋯ The spectral sensitivity of the dark-adapted rod response closely followed the difference spectrum of the rod photopigment for wave-lengths greater than 450 nm. This was true throughout the intensity range of the response, including low intensities where response averaging was necessary. 8. At low response amplitudes (approximately 1 mV), about 70% of the 40 rods tested showed responses to long wave-length stimuli consisting of two components...