The saphenous nerve-evoked slow v.r.p. was depressed by [Met5] enkephalin (0.1-1 EM), dynorphin (1-13X0.2 gM) and morphine (1-2 pM), and these effects were reversed by naloxone (1 pM).6 Two endogenous peptides, galanin (1-2 pM) and somatostatin (1-2.5 pM), inhibited the slow v.r.p. evoked by saphenous nerve stimulation, whereas another endogenous peptide, calcitonin generelated peptide (0.1-0.5 pM), potentiated the slow v.r.p. The slow v.r.p. was also inhibited by yaminobutyric acid (GABA, 20pM) and muscimol (0.2 pM), and their effects were antagonized by bicuculline (1 pM). 7 The present results suggest that substance P and neurokinin A are involved in the saphenous nerve-evoked C-fibre response in the spinal cord of the newborn rat.

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This study establishes a cortical map of the somatosensory periphery of the mouse head, with emphasis on the whisker pad. Data in the literature on the projection of the common hair follicles are confusing, notably the question whether or not this projection is separated from or overlaps with that of the facial vibrissae, the barrelfield. Microelectrode recordings in the barrelfield and its immediate surroundings upon natural stimulation of the periphery were followed by microlesions and histological reconstruction. Results show that the barrelfield consists of two parts: an anterior part where vibrissal follicles and the skin bearing them are represented, and a posterior part receiving only vibrissa inputs. The skin between these latter vibrissae is represented outside the barrelfield. We conclude that the partially dissociated cortical representation of skin and vibrissae may allow large vibrissae to be used in tasks requiring greater acuity than the shorter ones provide. This hypothesis is supported by the observation that, owing to special muscles, large vibrissae are more mobile than short ones. We also propose that the segregation of inputs from vibrissae and common fur is related to the number of nerve fibers serving one follicle, and we indicate an experimental model to test this possibility.

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