Subsecond reward-related dopamine release in the mouse dorsal striatum.

Reward presentation is known to induce transient bursts of midbrain dopamine neurons in monkeys and rats, and the reward-induced dopamine overflow has been detected in the rat ventral striatum. To detect reward-related dopamine release in the dorsal striatum of behaving mice (C57BL/6), we used voltammetry with carbon-fiber microelectrodes implanted into the dorsal striatum. Dopamine signals increased transiently after food delivery with a peak at 0.6 s after the delivery onset. The success in detecting transient reward-response of dopamine in behaving mice opens a wide range of application to studies in mutant mice.

Acute effects of bilateral subthalamic stimulation on decision-making in Parkinson's disease.

BACKGROUND: Pathological gambling can develop in Parkinson's disease (PD), and impairment of decision-making may play an important role in the mechanism. To assess acute effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on decision-making, patients with PD who were eligible for STN-DBS were evaluated using the Iowa Gambling Task (IGT). METHODS: The study participants were 16 patients with PD who underwent bilateral STN-DBS, and 16 age-matched control patients with PD. The participants performed the IGT pre-operatively and 2-4 weeks post-operatively with on- and off-stimulation. Participants' one hundred card selections were divided into five blocks of 20 cards each. RESULTS: The total IGT score was not significantly different before surgery, on-stimulation or off-stimulation, but DBS patients tended to perform worse in the on-DBS session compared to off-DBS session (P = 0.019) only in the last block of the task. The IGT score did not correlate with levodopa equivalent dose or performance on the measures of executive function, but did correlate with self-reported depression symptoms, and active contact of stimulation. CONCLUSION: Bilateral STN-DBS may affect decision-making in acute post-operative stage.

Phasic reward responses in the monkey striatum as detected by voltammetry with diamond microelectrodes.

Reward-induced burst firing of dopaminergic neurons has mainly been studied in the primate midbrain. Voltammetry allows high-speed detection of dopamine release in the projection area. Although voltammetry has revealed presynaptic modulation of dopamine release in the striatum, to date, reward-induced release in awakened brains has been recorded only in rodents. To make such recordings, it is possible to use conventional carbon fibres in monkey brains but the use of these fibres is limited by their physical fragility. In this study, constant-potential amperometry was applied to novel diamond microelectrodes for high-speed detection of dopamine. In primate brains during Pavlovian cue-reward trials, a sharp response to a reward cue was detected in the caudate of Japanese monkeys. Overall, this method allows measurements of monoamine release in specific target areas of large brains, the findings from which will expand the knowledge of reward responses obtained by unit recordings.

Impaired in vivo dopamine release in parkin knockout mice.

parkin is the most frequent causative gene among familial Parkinson's disease (PD). Although parkin deficiency induces autosomal recessive juvenile parkinsonism (AR-JP, PARK2) in humans, parkin knockout (PKO) mice consistently show few signs of dopaminergic degeneration. We aimed to directly measure evoked extracellular dopamine (DA) overflow in the striatum with in vivo voltammetry. The amplitude of evoked DA overflow was low in PKO mice. The half-life time of evoked DA overflow was long in PKO mice suggesting lower release and uptake of dopamine. Facilitation of DA overflow by repetitive stimulation enhanced in the older PKO mice. Decreased dopamine release and uptake in young PKO mice suggest early pre-symptomatic changes in dopamine neurotransmission, while the enhanced facilitation in the older PKO mice may reflect a compensatory adaptation in dopamine function during the late pre-symptomatic phase of Parkinson's disease. Our results showed parkin deficiency may affect DA release in PKO mice, although it does not cause massive nigral degeneration or parkinsonian symptoms as in humans.

Isolated reversible splenial lesion in adult meningitis: a case report and review of the literature.

We report the rare case of a 38-year-old man who suffered from aseptic meningitis. Brain magnetic resonance imaging showed an ovoid lesion with a high signal intensity on T2- and diffusion-weighted images in the splenium of the corpus callosum that completely disappeared within a week. There were no symptoms or signs associated with the lesion, and the prognosis was good. Although rare in adult patients, awareness of a reversible splenial lesion in meningoencephalitis is important.