ABSTRACT
Objective To investigate the changes in inhibitory guanine nucleotide binding protein Gi_2 in five brain regions of morphine addicted rats: ventral tegmental area, nucleus accumbens, prefrontal cortex, hippocampus and locus caeruleus. Methods 36 adult male SD rats were randomly divided into six groups (n=6): acute morphine dependent group, acute abstinence group, acute control group, chronic morphine dependent group, chronic abstinent group and chronic control group. Morphine dependent models were reproduced. Withdrawal syndrome was induced with naloxone 5mg/kg for 30min in rats of abstinence group. All rats were sacrificed by decapitation. Frozen sections of coronal plane of respective brain regions (ventral tegmental area, nucleus accumbens, prefrontal cortex, locus coeruleus, hippocampus) were prepared. The relative concentrations of Gi_2 protein were determined with immunohistochemical methods. Results Gi_2 proteins in acute morphine dependent group and acute abstinence group were significantly decreased compared with that of acute control group in nucleus accumbens (P
ABSTRACT
Objective The molecular basis for opiate tolerance and dependence remains poorly understood despite extensive investigation in several preparations, including the hippocampus. Recent studies have implicated that the hippocampus played a central role in opiate tolerance, dependence and withdrawal. The current study is to explore the change in guanine nucleotide binding protein-inhabitant (Gi_2) protein in primary cultured hippocampal neurons with morphine treament. Methods The hippocampus was harvested from newborn Sprague-Dawley rats. Primary hippocampal neuronal cultures of 7 days in vitro were used and divided randomly into six groups (n=6), i.e. morphine treatment 4h group (M4), 8h group (M8), 16h group (M16), 24h group (M24), 48h group (M48) and control group (C). All morphine treatment groups were treated with morphine (10?mol/L). C group was treated with saline. The G protein levels were determined with immunofluorscence and laser scanning confocal microscope (LSCM) imaging techniques. Results Gi_2 protein levels in M16, M24 and M48 groups decreased significantly compared with that in C group (P0.05). Among M16, M24 and M48 groups, Gi_2 protein level was lowest in the M48 group. Conclusion The results indicated that Gi_2 protein levels decreased significantly in primary cultured hippocampal neurons with morphine treatment, which might be a potential molecular mechanism of opioid tolerance and dependence.
ABSTRACT
The subunit ?_0 of guanine nucleotide- binding protein, in the areas of rat brain and spinal cord was localized by immunohistochemical methods. It was found that in the rat brain, specific ?_0-like immunoreactivity(?_0-Li) displayed regional heterogeneity, a high density of ?_0-Li revealed in neuropil, and somatic membranes as well as the neuronal processes.Most intense ?_0-Li can be seen in substantia nigra(pars reticulata), interpcduncular nucleus, habenulo-interpeduncular tract, strata oriens and radiatum of the hippocampus, and substantia gelatinosa of the spinal cord. There are also areas of moderate staining ie: the molecular layer of cerebral and cerebellar cortex, habenula, caudate-putamen complexes, the midline nuclei of thalamus and hypothalamus, periaqueductal grey, grey layers of superior colliculus, the olivo-cerebellar tract and the spinal tract of the trigeminal nerve as well. By contrast, the immunoreactvity of ?_0 in septal nuclei, globus pallidus, red nucleus, and the regions adjacent canalis centralis of the spinal cord showed much weaker. In addition, on the membranes and the processes of the neuronal cell bodies in the periaqueductal grey, substantia nigra, reticular formation, medial geniculate body and the nucleus of the trapezoid body were ?_0-Li positive.The results of AChE staining revealed that the AChE-positivc nerve terminals was coinsident with the presence of ?_0-Li in the following regions. For instance: the molecular layer of cerebral cortex, hippocampus, spinal tract of the trigminal nerve, and substantia gelatinosa of the spinal cord, where both the ?_0-Li and the AChE activity were positive. It is suggested that ?_0 subunit of Go-protein in brain might play roles in membrane signal transduction, and might have some relationship with cholinergic nerve.