I. Fabian et A. Ableitner, BRAIN SITES INVOLVED IN MU-OPIOID RECEPTOR-MEDIATED ACTIONS - A 2-DEOXYGLUCOSE STUDY, Brain research, 697(1-2), 1995, pp. 205-215
Brain regions that may be functionally involved in the neuropharmacolo
gical actions of mu-opioid agonists have been examined in conscious ra
ts using the quantitative [C-14]2-deoxyglucose autoradiographic techni
que. At 0.5 mu g and 1 mu g intracerebroventricularly the highly selec
tive mu-opioid receptor agonist D-Ala(2), MePhe(4), Gly-ol(5)-enkephal
in effected statistically significant increases as well as statistical
ly significant decreases in regional glucose utilization: in limbic st
ructures, such as hippocampal formation, medial amygdala and lateral s
eptum, glucose utilization was most prominently increased after D-Ala(
2), MePhe(4), Gly-ol(5)-enkephalin; glucose utilization was further in
creased in the lateral habenular nucleus, the hypothalamus, ventromedi
al nucleus and dorsal raphe; whereas decreases were found in the mamil
lary body and anterior thalamus. Glucose utilization in structures ass
ociated with somatosensory and nociceptive processing was increased in
the central gray of the midbrain and decreased in the nucleus gelatin
osus. Only increases in glucose utilization were produced by D-Ala(2),
MePhe(4), Gly-ol(5)-enkephalin in brain regions involved in motor con
trol, including the globus pallidus, the substantia nigra, pars reticu
lata, the nucleus ruber and the cerebellum, and brain regions involved
in visual processing - the visual cortex and superior colliculus deep
layer. It is concluded that this pattern of regional changes underlie
s the mu-opioid receptor-mediated antinociceptive-, epileptogenic-, me
mory- and mood-modulating actions of mu-opioid agonists.