Experimental physiology
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Experimental physiology · Jul 2002
Comparative Study Clinical Trial Controlled Clinical TrialThe effects of isometric exercise training on resting blood pressure and orthostatic tolerance in humans.
Isometric exercise training has been shown to reduce resting blood pressure, but the effect that this might have on orthostatic tolerance is poorly understood. Changes in orthostatic tolerance may also be dependent on whether the upper or lower limbs of the body are trained using isometric exercise. Twenty-seven subjects were allocated to either a training or control group. ⋯ Rather, it is possible that the training altered some other aspect of cardiovascular control during orthostatic stress that was apparent in the changes in heart rate. Leg-training was accompanied by increases in estimated lean leg volume. The effects of isometric training on orthostatic tolerance appear to be specific to limbs that are directly involved in LBNP testing.
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Experimental physiology · Mar 2002
Comparative StudyNoxious somatic inputs to hypothalamic-midbrain projection neurones: a comparison of the columnar organisation of somatic and visceral inputs to the periaqueductal grey in the rat.
The induction of Fos protein was used to localise hypothalamic neurones activated by noxious somatic stimulation. This was combined with retrograde transport of fluorescent latex microspheres from identified 'pressor' and 'depressor' sites in the dorsolateral/lateral or ventrolateral columns of the periaqueductal grey (PAG). Fos-positive neurones were found throughout the rostral hypothalamus. ⋯ Only one neurone was double labelled following injection of tracer at a depressor site in the ventrolateral PAG. This is in marked contrast to visceroresponsive hypothalamic neurones, a larger proportion of which project to the PAG and which, as reported previously, preferentially target depressor sites in the ventrolateral sector. These results are discussed in relation to the roles of the anterior hypothalamus and the different functional columns of the PAG in co-ordinating autonomic and sensory functions in response to nociceptive inputs originating in different peripheral domains.
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Experimental physiology · Mar 2002
ReviewAnatomy of primary afferents and projection neurones in the rat spinal dorsal horn with particular emphasis on substance P and the neurokinin 1 receptor.
The dorsal horn of the spinal cord plays an important role in transmitting information from nociceptive primary afferent neurones to the brain; however, our knowledge of its neuronal and synaptic organisation is still limited. Nociceptive afferents terminate mainly in laminae I and II and some of these contain substance P. Many projection neurones are located in lamina I and these send axons to various parts of the brain, including the caudal ventrolateral medulla (CVLM), parabrachial area, periaqueductal grey matter and thalamus. ⋯ Both types of neurone are innervated by descending serotoninergic axons from the medullary raphe nuclei. The lamina III/IV neurones also receive numerous synapses from axons of local inhibitory interneurones which contain GABA and neuropeptide Y, and again this input shows some specificity since post-synaptic dorsal column neurones which also have cell bodies in laminae III and IV receive few contacts from neuropeptide Y-containing axons. These observations indicate that there are specific patterns of synaptic connectivity within the spinal dorsal horn.
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Experimental physiology · Mar 2002
C-nociceptor activation of hypothalamic neurones and the columnar organisation of their projections to the periaqueductal grey in the rat.
The induction of Fos protein was used to localise hypothalamic neurones activated by ramps of noxious skin heating delivered at a rate of 2.5 degrees C s(-1) to preferentially activate C-nociceptors. This was combined with retrograde transport of cholera toxin subunit B from identified 'pressor' and 'depressor' sites in the dorsolateral/lateral or the ventrolateral columns of the periaqueductal grey. ⋯ More than 20 % of Fos-positive neurones in this region projected to depressor sites in the ventrolateral periaqueductal grey, and 10 % projected to its dorsolateral/lateral sector. These results are discussed in relation to the peripheral inputs to hypothalamic-midbrain pathways and their role in the cardiovascular responses to different components of the pain signal.
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Experimental physiology · May 2001
Reflex nature of the cardiorespiratory response to primary thoracic blast injury in the anaesthetised rat.
Blast injuries represent a problem for civilian and military populations. Primary thoracic blast injury causes a triad of bradycardia, hypotension and apnoea. The objective of this study was to investigate the reflex nature of this response and its modulation by vagotomy or administration of atropine. ⋯ V.) caused a significant reduction in the bradycardia (HP increasing from 124 +/- 3 ms to 142 +/- 4 ms) but did not modulate either the hypotension or apnoea. It is concluded that a reflex involving the vagus nerve mediates the bradycardia, apnoea and a component of the hypotension associated with thoracic blast. The pattern of this response is similar to effects that follow stimulation of the pulmonary afferent C-fibres.