TY - JOUR
T1 - Opiate receptor ontogeny and morphine-induced effects
T2 - Influence of chronic footshock stress in preweanling rats
AU - Bardo, M. T.
AU - Bhatnagar, R. K.
AU - Gebhart, G. F.
PY - 1981/7
Y1 - 1981/7
N2 - The ontogeny of opiate receptors was examined in various CNS regions of preweanling rats which received either daily inescapable footshock stress, exposure to a footshock apparatus without shock, or no handling from birth to 21 days of age. At 21 days of age, each of these treatment groups was also assessed for morphine-induced changes in activity, hot-plate paw-lick latency, and core body temperature. Marked regional differences in [3H]naloxone binding capacity were observed from 7 to 21 days of age in spinal cord, medulla-pons, midbrain, hypothalamus, striatum, and cortex. Caudal regions approached adult-like [3H]naloxone binding before rostral regions. The normal ontogeny of opiate receptors was not significantly influenced by the chronic footshock treatment. However, footshock treatment significantly reduced the efficacy of morphine (2 mg/kg) in producing hypoactive and antinociceptive effects, but not in producing a hyperthermic effect. These results demonstrate that stress-related changes in the behavioral efficacy of morphine do not necessarily depend upon changes in those opiate receptor populations that bind naloxone.
AB - The ontogeny of opiate receptors was examined in various CNS regions of preweanling rats which received either daily inescapable footshock stress, exposure to a footshock apparatus without shock, or no handling from birth to 21 days of age. At 21 days of age, each of these treatment groups was also assessed for morphine-induced changes in activity, hot-plate paw-lick latency, and core body temperature. Marked regional differences in [3H]naloxone binding capacity were observed from 7 to 21 days of age in spinal cord, medulla-pons, midbrain, hypothalamus, striatum, and cortex. Caudal regions approached adult-like [3H]naloxone binding before rostral regions. The normal ontogeny of opiate receptors was not significantly influenced by the chronic footshock treatment. However, footshock treatment significantly reduced the efficacy of morphine (2 mg/kg) in producing hypoactive and antinociceptive effects, but not in producing a hyperthermic effect. These results demonstrate that stress-related changes in the behavioral efficacy of morphine do not necessarily depend upon changes in those opiate receptor populations that bind naloxone.
KW - antinociception
KW - footshock stress
KW - hyperthermia
KW - hypoactivity
KW - morphine
KW - opiate receptor
KW - preweanling development
UR - http://www.scopus.com/inward/record.url?scp=0019828140&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0019828140&partnerID=8YFLogxK
U2 - 10.1016/0165-3806(81)90003-1
DO - 10.1016/0165-3806(81)90003-1
M3 - Article
C2 - 6266613
AN - SCOPUS:0019828140
SN - 0165-3806
VL - 1
SP - 487
EP - 495
JO - Developmental Brain Research
JF - Developmental Brain Research
IS - 4
ER -