Neuroscience
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The speed of execution of complex movements depends on both the local, differential properties of the trajectory and on some of its more global metric parameters. The effects of these global factors were studied in free, writing-like movements with either piece-wise constant, or regularly changing curvature. ⋯ Furthermore, it is shown that the average tangential velocity over identifiable segments of the trajectory also depends on the corresponding average curvature. The implications of these results vis-à-vis the central representation and planning of movements are discussed.
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Projections to the basal ganglia from four auditory cortical fields in the cat were studied by combining microelectrode-mapping of the neurons' best frequencies with autoradiographic and histochemical tract-tracing techniques. Each auditory field is a source of projections to the homolateral basal ganglia. The distribution of labeling within the basal ganglia is related to the cortical field in which the injection site is located. ⋯ By comparison, two adjacent sheets of tissue were labeled when two injections were made into the low best-frequency and high best-frequency representations of the same auditory field. Double-injection, double-tracer experiments revealed that adjacent sheets of tissue received projections from different best-frequency loci. These observations suggested a degree of tonotopic organization to this projection system which was equipoise to the evidence obtained for a topographic organization.
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The preganglionic sympathetic neurons in the intermediolateral cell column of the thoracic and upper lumbar segments of the spinal cord which innervate the chromaffin cells in the adrenal medulla, sympathoadrenal preganglionic neurons, were identified by the method of retrograde axonal transport of the fluorescent dyes Fast Blue and True Blue. In rats, Fast Blue or True Blue was injected into the medulla of the left adrenal gland. After a survival period of 5 days, the animals were perfusion fixed, the thoracic and lumbar spinal cord sectioned and processed for the immunofluorescent localization of met-enkephalin, neurophysin, oxytocin, serotonin, somatostatin and substance P immunoreactivity. ⋯ Serotonin immunoreactivity was depleted in the intermediolateral cell column below the level of the transection for five to six segments, but sparse networks of immunoreactive fibers were observed in both the intermediolateral cell column and the ventral horn in more caudal segments. Met-enkephalin, serotonin, somatostatin and substance P immunoreactivity were decreased in both the contralateral and ipsilateral intermediolateral cell column below the level of a spinal cord hemisection, suggesting that both crossed and uncrossed descending pathways exist. Neurophysin and oxytocin immunoreactivity were depleted below the level of the hemisection in the ipsilateral intermediolateral cell column without noticeable decrease in the level of immunoreactivity in the contralateral intermediolateral cell column, suggesting that a decussation does not occur at the level of the spinal cord, but may exist above the level of the hemisection...
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Both systemic and intrathecal capsaicin release and deplete substance P from primary sensory afferents and induce prolonged chemical and thermal analgesia. Given the existence of efferents containing substance P together with a pain-inhibitory serotoninergic pathway, the present study investigated the effects of intraventricular capsaicin upon basal nociception, analgesic responsivity to opiates and substance P immunoreactivity. Following treatment with capsaicin at doses of 25, 50 and 100 micrograms or with vehicle, alterations in basal rodent flinch-jump thresholds as well as analgesic responses to 5 and 2.5 mg/kg of morphine were measured over a post-injection time course. ⋯ Substance P-like immunoreactivity in capsaicin-treated rats was not appreciably depleted compared with vehicle controls in the substantia gelatinosa of the spinal cord and V cranial nerve, the raphe magnus and periaqueductal gray, the medullary, pontine and mesencephalic reticular formation, the substantia nigra, the corpus striatum and the central nucleus of the amygdala. By contrast, substance P-like immunoreactivity appeared to increase in the medial nucleus of the amygdala. In the absence of depletion of substance P immunoreactivity by the intraventricular capsaicin, the observed alterations in opiate analgesic responses may possibly be due to alterations in other transmitters or peptide systems.