ABSTRACT
Neurosensory tactile functions were investigated in human subjects by two different and complementary experimental approaches. First, a conventional psychophysical method (two-point gap discrimination) was used to determine the tactile discrimination threshold by analyzing the subjects' ability to detect a gap of variable width between two contact points when a series of stimuli was applied to the skin. Using this method we confirmed the marked degradation of tactile spatial acuity with age and showed that skin discriminative function was partially restored after hydration of the skin with a moisturizer. The second approach consisted of a microneurographic recording of tactile afferent fibers in response to two types of mechanical stimuli applied reproducibly to the corresponding receptive fields. With this method, we found that the afferent messages were depressed following hydration of the skin surface. Thus, partial restoration of tactile spatial acuity after hydration appears to be due to both a softening of the stratum corneum permitting better localization of the stimulus and a weaker transfer of the stimulus toward the sensory receptors.
Subject(s)
Body Water/metabolism , Discrimination, Psychological/physiology , Skin Physiological Phenomena , Skin/innervation , Space Perception/physiology , Adult , Aged , Cheek/innervation , Cheek/physiology , Electric Conductivity , Gap Junctions/physiology , Humans , Mechanoreceptors , Sensory Thresholds/physiology , Skin/metabolismABSTRACT
Ketamine is normally considered as being anti-dysrhythmic. A case report is presented here in which small subanaesthetic doses of ketamine were administered to reinforce spinal analgesia. Initial doses were followed by a dysrhythmia, which appeared to be repeatedly counteracted by further small doses of the drug. The cardiac pharmacology of ketamine is discussed, as is the relevance of the chance finding of mitral valve prolapse.
