The Journal of physiology
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The Journal of physiology · Aug 1987
Reciprocal Ia inhibition between ankle flexors and extensors in man.
1. Reciprocal inhibition between antagonist muscle groups at the ankle has been investigated in sixty healthy subjects. Hoffmann reflexes (H reflexes) in the soleus and tibialis anterior muscles were used to assess changes in reciprocal inhibition evoked by electrical stimulation of antagonist muscle nerves. 2. ⋯ The increase in inhibition before and at the very beginning of the contraction cannot be due to sensory feed-back during contraction, but must depend on a supraspinal control of the spinal cord. 5. At conditioning-test intervals of 4-6 ms, the inhibition of the soleus H reflex from the peroneal nerve was considerably larger during tonic dorsiflexion than at rest. Thus, tonic dorsiflexion revealed an inhibition with long latency from the peroneal nerve, which was not seen at rest.(ABSTRACT TRUNCATED AT 400 WORDS)
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The Journal of physiology · Jul 1987
Somatic and visceral inputs to the thoracic spinal cord of the cat: marginal zone (lamina I) of the dorsal horn.
1. Single-unit electrical activity has been recorded from fifty-five neurones whose recording sites were located in or immediately adjacent to the marginal zone (lamina I) of the lower thoracic spinal cord (T8-T12) of anaesthetized or decerebrate cats. Their responses to stimulation of somatic and visceral afferent fibres and the sizes of their cutaneous receptive fields have been analysed and compared with the responses and receptive fields of neurones recorded throughout the spinal grey matter. 2. ⋯ The majority of somatic and viscero-somatic neurones in lamina I had small somatic receptive fields but, even in this group of cells, viscero-somatic neurones had larger receptive fields than somatic cells. 6. Ascending axonal projections in both dorsolateral funiculi and in the contralateral ventrolateral quadrant were tested in eighteen lamina I neurones. Only one neurone was found to project to the cervical cord.(ABSTRACT TRUNCATED AT 400 WORDS)
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The Journal of physiology · Jul 1987
Responses of spinothalamic tract cells in the superficial dorsal horn of the primate lumbar spinal cord.
1. The responses of thirty-five spinothalamic tract (s.t.t.) cells in or near lamina I of the dorsal horn were examined in chloralose- and barbiturate-anaesthetized monkeys (Macaca fascicularis). Many of the cells could be classified on the basis of receptive field properties as either wide dynamic range (w.d.r.) cells or as high-threshold (h.t.) cells. 2. ⋯ It is concluded that s.t.t. cells in or near lamina I can signal noxious cutaneous stimuli but have poor coding abilities for innocuous mechanical stimuli. Some of these cells respond to innocuous thermal stimuli, but their role in thermoreception is unclear. The small receptive fields suggest that these cells could contribute to stimulus localization.
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The Journal of physiology · Jul 1987
Steady-state fluid filtration at different capillary pressures in perfused frog mesenteric capillaries.
1. The theory of steady-state filtration through capillary walls (Michel, 1984) has been developed and investigated in experiments on single capillaries of the frog mesentery perfused with Ringer solutions containing bovine serum albumin (BSA) and Ficoll 70. 2. In each experiment, the micro-occlusion technique of Michel, Mason, Curry, Tooke & Hunter (1974) has been used to investigate the relation between fluid movements per unit area of capillary wall (Jv/A) and capillary pressure (Pc) under two sets of conditions in the same vessel. ⋯ E. of mean +/- 0.04) and in eight different vessels mean sigma to Ficoll 70 in the presence of BSA (10 mg ml-1) was 0.98 (S. E. of mean +/- 0.05). The steady-state data were consistent with the prediction that the oncotic pressure opposing high filtration rates approximates to sigma 2 pi c in the steady state, where pi c is the perfusate oncotic pressure.(ABSTRACT TRUNCATED AT 400 WORDS)
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The Journal of physiology · May 1987
Lung reflexes and nasal vascular resistance in the anaesthetized dog.
1. In pentobarbitone-anaesthetized dogs the nasal vasculature was perfused on both sides, and nasal vascular and airflow resistances were measured together with blood pressure, heart rate and tidal airflow. 2. Capsaicin was injected intravenously to stimulate lung C-fibre receptors, and veratrine to stimulate pulmonary stretch receptors and cardiac receptors. ⋯ Thus cardiac receptors seem to increase nasal vascular resistance. 5. Injections of capsaicin and veratrine into the nasal circulation decreased nasal vascular resistance, with a stimulation of breathing and changes in blood pressure. Denervations indicated that these were a combination of local and reflex actions.