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Deviation of dopamine homeostasis is known to be associated with disorders like drug addiction and Parkinson's disease. As dopamine function is tightly regulated within the basal ganglia circuitry, cortical perturbation would lead to modulation of dopaminergic activity in the striatum. We proposed and tested if somatosensory activity such as forepaw stimulation could modulate dopaminergic function. Specifically, we tested in rats if electrical forepaw stimulation (EFS) could attenuate dopamine release in the brain if dopamine is excessive, and boost dopamine release if dopamine is deficient. We had previously demonstrated that EFS effectively attenuated excessive DA concentration in the striatum. We now show in this manuscript with fMRI that EFS boosted DA release on two DA deficient conditions: (1) with quinpirole challenge, and (2) partial Parkinsonism model (PD). Quinpirole alone decreased dopamine release and thus the cerebral blood volume (CBV) that was restored by EFS. EFS also succeeded in increasing CBV in the basal-ganglia circuitry of the PD rats, but not in the controls. Context-dependent connectivity analysis showed increased connectivity during the basal state in the PD rats, compared with the controls. This 'enhanced' yet abnormal connectivity of PD rats was reduced post-EFS. Our results suggest that EFS resets the deficient DA system by partially increasing DA release, in the meanwhile lessening the need for recruiting extra functional network in the basal ganglia circuitry. This study shows not only the capacity of peripheral stimulation to perturb neurotransmitter function, but also the potential of peripheral stimulation to restore neurotransmitter homeostasis. Synapse, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background: Methylphenidate (MPH), the most commonly prescribed medication for childhood attention-deficit/hyperactivity disorder (ADHD), shares chemical and mechanistic similarities to cocaine which has stimulated research to address the addiction liability following treatment. Methods: Utilizing locomotor sensitization we examined the consequences of recurrent MPH versus cocaine treatment during preadolescence in altering cocaine-induced locomotor behavior in adolescent and adult mice. Black Swiss Webster mice were treated with MPH, cocaine, or saline during preadolescence. To test whether MPH pretreatment during preadolescence contributed to an altered sensitivity to cocaine during adolescence, these mice were treated with recurrent cocaine or saline during adolescence. All mice were challenged with cocaine as adults. Results: Recurrent MPH treatment, unlike cocaine treatment in preadolescent mice, had no effect on locomotor sensitization to cocaine during adolescence or adulthood, as compared with saline controls. Furthermore, unlike cocaine, administration of MPH in adolescence did not augment the response to cocaine challenge. Conclusions: MPH treatment during preadolescence does not increase subsequent sensitivity to cocaine, whereas cocaine treatment does. Thus, MPH treatment during preadolescence does not appear to persistently induce long-term adaptations, which may underlie an enhanced liability for subsequent drug abuse. [Copyright &y& Elsevier]

Aim: To investigate the toxic effects of mid-pregnancy cocaine exposure on embryo-fetus., Methods: A transplacental murine model of cocaine exposure on embryo-fetus mice was established, in which pregnant dams of comparable weight were assigned into three groups: cocaine with food ad lib (COC), saline and pair-fed with COC (SPF), and saline with food ad lib (SAL). From embryonic d 8 (E8) to E17, physiological variables of dams and offspring were recorded and concentrations of dopamine and serotonin in fetal striatum were examined., Results: Compared with SAL dams, COC and SPF dams showed lower weight gain. But only COC fetuses demonstrated low brain weight and low striatum weight on E17, as well as small biparietal diameter (BPD) on postnatal d1 (P1). Surprisingly, low brain/body weight ratio was seen in COC offspring, which might reflect disproportionate growth delay in these fetuses. Neurotransmitter and histological analysis revealed high level of dopamine and serotonin in COC fetal striatum, as well as morphological alterations of liver., Conclusion: Mid-pregnancy cocaine exposure induces fetal growth delay in utero, especially disproportionate brain developmental retardation. Maternal undernutrition does not play a key role in fetal developmental retardation when exposed to cocaine in utero.

The aim of the experiments was to develop and characterize a murine model for investigating the effects of prenatal cocaine exposure on the mother and fetus. Pregnant mice were separated into three groups: group 1 was treated with cocaine HCl at 10 mg/kg twice daily (COC); group 2 was treated with saline at 10 ml/kg twice daily (SAL); and group 3 was pair-fed with the COC dams and was injected with saline following the same schedule (SPF) from embryonic day (E) 8 to 17. We utilized high-pressure liquid chromatography (HPLC) with UV detector and electrochemical detector to test the concentrations of cocaine, dopamine and serotonin, as well as HE staining to observe morphological alterations of liver and placenta. Though less food intake and lower weight gain were observed in COC and SPF groups but not in SAL dams, lower fetal body weight and brain weight were only seen in COC offspring. Pharmacological analysis revealed that cocaine was found in fetal plasma at 15 min following intraperitoneal administration on E17, accompanied with elevated concentrations of dopamine (DA) and serotonin (5-HT) in fetal brain. We also observed morphological changes in liver and placenta of cocaine-exposed fetuses. The present study indicates that pregnancy cocaine exposure can lead to maternal undernutrition and developmental abnormality of the fetal brain, liver and placenta. It is suggested that the developmental abnormality of the fetuses induced by cocaine is due to the toxicological effect of cocaine but not to maternal undernutrition.