Abstract
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1.
Subcutaneous or intrahypothalamic injections of capsaicin produce hypothermia in the neonate rat. Repeated injections with increasing doses of capsaicin result in unresponsiveness to this drug (capsaicin-desensitization).
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2.
Young rats aged 8–10 days which had received serial injections of capsaicin solution (a cumulative dose of 4.63 mg per animal) or of the solvent alone were subsequently tested as adults for their ability to thermoregulate.
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3.
On exposure to an ambient temperature of 41° C, adult rats which had been capsaicin-desensitized as neonates were unable to thermoregulate against overheating by means of autonomic responses whereas control littermates could maintain normal rectal temperature. However, autonomic thermoregulation against cold was unimpaired in the desensitized rats.
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4.
Skin-cooling operant behavior in heat stress was impaired in adult rats which had been capsaicin-desensitized as neonates whereas their skin-heating behavior was not different from that of control littermates.
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5.
These results suggest that the central and peripheral warm-receptors responsible for thermoregulation in the neonate rat are functionally mature at least inasmuch as they form a part of thermoregulatory system involved in lowering body temperature and can be desensitized by capsaicin. Moreover, such receptors, once desensitized 8–10 days after birth, apparently do not regain their function and are not regenerated or replaced during subsequent maturation of the animal.
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References
Boulant JA, Hardy JD (1974) The effect of spinal and skin temperatures on the firing rate and thermosensitivity of preoptic neurones. J Physiol (Lond) 240: 639–660
Cabanac M, Cormareche-Leydier M, Poirier LJ (1976) The effect of capsaicin on temperature regulation of the rat. Pflügers Arch 366: 217–221
Conklin P, Heggeness FW (1971) Maturation of temperature homeostasis in the rat. Am J Physiol 220: 333–336
Fowler SJ, Kellogg C (1975) Ontogeny of thermoregulatory mechanisms in the rat. J Comp Physiol Psychol 89: 738–746
Hori T (1980) The capsaicin desensitized rat: behavioral thermoregulation and thermosensitivity of hypothalamic neurons. In: Cox B, Lomax P, Milton AS, Schönbaum E (eds) Thermoregulatory mechanisms and their therapeutic implications, Karger, Basel, pp 214–215
Hori T, Harada Y (1977) The effect of capsaicin on behavioral thermoregulation. J Physiol Soc Japan 39: 266–267
Hori T, Shinohara K (1979) Hypothalamic thermo-responsive neurones in the new-born rat. J Physiol (Lond) 294: 541–560
Hori T, Tsuzuki S (1979a) Thermosensitivity of preoptic neurons in the capsaicin-desensitized rat. J Physiol Soc Japan 41: 430
Hori T, Tsuzuki S (1979b) Thermoregulatory behavior of rats desensitized by capsaicin in the early postnatal life. J Physiol Soc Japan 41: 445
Jancsó G, Kiraly E, Jancsó-Gábor A (1977) Pharmacologically induced selective degeneration of chemosensitive primary sensory neurones. Nature (Lond) 270: 741–743
Jancsó N, Jancsó-Gábor A, Szolcsányi J (1967) Direct evidence for neurogenic inflammation and its prevention by denervation and by pretreatment with capsaicin. Br J Pharmacol Chemother 31: 138–151
Jancsó-Gábor A, Szolcsányi J, Jancsó N (1970a) Irreversible impairment of thermoregulation induced by capsaicin and similar pungent substances in rats and guinea-pigs. J Physiol (Lond) 206: 495–507
Jancsó-Gábor A, Szolcsányi J, Jancsó N (1970b) Stimulation and desensitization of the hypothalamic heat-sensitive structures by capsaicin in rats. J Physiol (Lond) 208: 449–459
Joó F, Szolcsányi J, Jancsó-Gábor A (1969) Mitochondrial alterations in the spinal ganglion cells of the rat accompanying the long-lasting sensory disturbance induced by capsaicin. Life Sci 8: Pt I, 621–626
Nakayama T, Suzuki M, Ishikawa Y, Nishio A (1978) Effects of capsaicin on hypothalamic thermo-sensitive neurons in the rat. Neurosci Lett 7: 151–155
Szolcsányi J (1977) A pharmacological approach to elucidation of the role of different nerve fibres and receptor endings in mediation of pain. J Physiol (Paris) 73: 251–259
Szolcsányi J, Jancsó-Gábor A (1973) Capsaicin and other pungent agents as pharmacological tools in studies on thermoregulation. In: Schönbaum E, Lomax P (eds) The pharmacology of thermoregulation. Karger, Basel, pp 395–409
Szolcsányi J, Jancsó-Gábor A (1975) Analysis of the role of warmth detectors by means of capsaicin under different conditions. In: Lomax P, Schönbaum E, Jacob J (eds) Temperature regulation and drug action. Karger, Basel, pp 331–338
Szolcsányi J, Janscó-Gábor A, Joó F (1975) Functional and fine structural characteristics of the sensory neuron blocking effect of capsaicin. Naunyn-Schmiedeberg's Arch Pharmacol 287: 157–169
Szolcsányi J, Joó F, Jancsó-Gábor A (1971) Mitochondrial changes in preoptic neurons after capsaicin desensitization of the hypothalamic thermodetectors in rats. Nature (Lond) 229: 116–117
Taylor PM (1960) Oxygen consumption in new-born rats. J Physiol (Lond) 154: 153–168
Thompson GE, Moore RE (1968) A study of newborn rats exposed to the cold. Can J Physiol Pharmacol 46: 865–871
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Hori, T., Tsuzuki, S. Thermoregulation in adult rats which have been treated with capsaicin as neonates. Pflugers Arch. 390, 219–223 (1981). https://doi.org/10.1007/BF00658265
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DOI: https://doi.org/10.1007/BF00658265