TY - JOUR
T1 - Hyperalgesic response to noxious stimulation in genetically polydipsic mice
AU - Kamikawa, Hideki
AU - Katafuchi, Toshihiko
AU - Hosoi, Masako
AU - Yamamoto, Tsuneyuki
AU - Hori, Tetsuro
N1 - Funding Information:
This work was supported by Grants-in-Aid for Scientific Research ((A) 10307001 and (B) 09557006 to T. Hori and (B) 10557008 to T. Katafuchi) from the Ministry of Education, Science, Sports and Culture of Japan.
PY - 1999/11/6
Y1 - 1999/11/6
N2 - Inbred mice, STR/N, are known to exhibit extreme polydipsia and polyuria but no abnormality in the response to exogenous vasopressin (AVP) and renal functions. Our previous studies have revealed that the brain opioid system is involved in the polydipsia of these mice. We here report that the STR/N mice show a decrease in the nociceptive threshold and a low, anti-nociceptive sensitivity to opioid receptors agonists. The paw-withdrawal latency (PWL) on a hot-plate in the STR/N mice was significantly shorter than that in their controls (BALB/c and C3H mice). This hyperalgesia was not affected by water restriction. Subcutaneous (s.c.) injections of morphine (5 mg/kg) and a κ-opioid receptor agonist, U50,488H (16 mg/kg) had no effect on the PWL in the STR/N mice, whereas the control mice prolonged PWL after administration of the opioids. However, the STR/N mice gained the ability to show morphine analgesia after up-regulation of the opioid system by repeated administration of naltrexone (s.c., 5 mg/kg) for 3 consecutive days. The results suggest that the anti-nociceptive function of the opioid system is down-regulated in STR/N mice as is observed in chronic morphine-treated animals. Copyright (C) 1999 Elsevier Science B.V.
AB - Inbred mice, STR/N, are known to exhibit extreme polydipsia and polyuria but no abnormality in the response to exogenous vasopressin (AVP) and renal functions. Our previous studies have revealed that the brain opioid system is involved in the polydipsia of these mice. We here report that the STR/N mice show a decrease in the nociceptive threshold and a low, anti-nociceptive sensitivity to opioid receptors agonists. The paw-withdrawal latency (PWL) on a hot-plate in the STR/N mice was significantly shorter than that in their controls (BALB/c and C3H mice). This hyperalgesia was not affected by water restriction. Subcutaneous (s.c.) injections of morphine (5 mg/kg) and a κ-opioid receptor agonist, U50,488H (16 mg/kg) had no effect on the PWL in the STR/N mice, whereas the control mice prolonged PWL after administration of the opioids. However, the STR/N mice gained the ability to show morphine analgesia after up-regulation of the opioid system by repeated administration of naltrexone (s.c., 5 mg/kg) for 3 consecutive days. The results suggest that the anti-nociceptive function of the opioid system is down-regulated in STR/N mice as is observed in chronic morphine-treated animals. Copyright (C) 1999 Elsevier Science B.V.
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U2 - 10.1016/S0006-8993(99)02006-5
DO - 10.1016/S0006-8993(99)02006-5
M3 - Article
C2 - 10556633
AN - SCOPUS:0032750265
VL - 846
SP - 171
EP - 176
JO - Molecular Brain Research
JF - Molecular Brain Research
SN - 0006-8993
IS - 2
ER -