No abstract

Morphine withdrawal is characterized by functional alterations at the level of the ventrotegmental area. We investigated the effects of chronic morphine administration and withdrawal on the morphological properties of immuno-labelled tyrosine hydroxylase-positive neurons of the rat ventrotegmental area with a confocal laser scanning microscope. Morphological evaluation revealed a reduction in the area and perimeter of tyrosine hydroxylase-positive somata in morphine-withdrawn rats. Conversely, the number of cells per field was found to have increased in the naloxone group. Collectively, the present results indicate that withdrawal from a chronic morphine treatment, and not chronic morphine per se, modifies cellular morphology of tyrosine hydroxylase-positive, presumably dopamine-containing, neurons of the rat VTA. This is consistent with the idea that withdrawal from morphine alters functioning of the mesolimbic dopamine system and provides a direct morphological correlate for the functional abnormalities typical of morphine withdrawal.

Apart from raclopride and olanzapine, the APs with lower extrapyramidal effects could be distinguished from typical APs on the basis of their ability to preferentially stimulate DA transmission in the NAc shell. There was no relationship between stimulation of PFCX DA and atypical APs profile. The differences between this study and voltammetry studies were not attributable to pargyline pretreatment.

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Caffeine enhances the reinforcing effects of cocaine and its motivational value. Our results highlight the role of active adulterants commonly used in cocaine-based illicit street drugs.