Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · Oct 1992
Modifications of striatal D2 dopaminergic postsynaptic sensitivity during development of morphine tolerance-dependence in mice.
Alterations in the activity of striatal dopaminergic neurons have been implicated in the development of morphine tolerance-dependence in rodents. To further explore this possibility, we examined the activity of these neurons in mice exposed to morphine during 4 days (addiction group) and subsequently treated with naloxone (withdrawal group). The efficiency of opiate treatment was assessed behaviorally. ⋯ Treatment with naloxone of morphine-exposed mice resulted in the typical jumping behavior indicative of opiate withdrawal. The differences in D2 receptors between placebo- and morphine-exposed mice disappeared after naloxone-induced opiate withdrawal, although this effect was due more to the inhibitory effect of naloxone on the density of these receptors in placebo-exposed mice rather than to a stimulatory effect in morphine-addicted mice. The morphine-induced increase in cAMP content also disappeared after naloxone treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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Cocaine HCl (0, 10, or 50 mg/kg) was injected into adult male ICR mice IP. Thirty minutes later, brains were removed and nine regions were isolated: olfactory bulbs (OB), olfactory tubercles (OT), prefrontal cortex (PC), septum (SP), striatum (ST), amygdala (AMY), hypothalamus (HT), hippocampus (HC), and thalamus (TH). Using high-performance liquid chromatography, concentrations of norepinephrine (NE), dopamine (DA), serotonin (5-HT), and their major metabolites were determined. ⋯ At 50 mg/kg cocaine, there was an increase in DA in the TH. There was a decrease in DOPAC, HVA, and 3-MT, as well as the DOPAC/DA ratio in the ST. In the OT, there was a decrease in DOPAC, the DOPAC/DA ratio, 3-MT, and the 3-MT/DA ratio.(ABSTRACT TRUNCATED AT 250 WORDS)