Individual variability in reward-based learning has been ascribed to quantitative variation in baseline levels of striatal dopamine. However, direct evidence for this pervasive hypothesis has hitherto been unavailable. We demonstrate that individual differences in reward-based reversal learning reflect variation in baseline striatal dopamine synthesis capacity, as measured with neurochemical po...

Spontaneous eye blink rate (EBR) has been proposed as a noninvasive, inexpensive marker of dopamine functioning. Support for a relation between EBR and dopamine function comes from observations that EBR is altered in populations with dopamine dysfunction and EBR changes under a dopaminergic manipulation. However, the evidence across the literature is inconsistent and incomplete. A direct correl...

The classical dopamine hypothesis of schizophrenia postulates a hyperactivity of dopaminergic transmission at the D(2) receptor. We measured in vivo occupancy of striatal D(2) receptors by dopamine in 18 untreated patients with schizophrenia and 18 matched controls, by comparing D(2) receptor availability before and during pharmacologically induced acute dopamine depletion. Acute depletion of i...

Dopamine use in acute renal failure (ARF) patients has been considered standard practice for many years. Despite this widely accepted practice, there has been limited evidence to support its usage. Low-dose dopamine has been accepted because it is considered to pose minimal risk to the patient. Dopamine infused at low doses is thought to be specific to dopaminergic receptors. However its result...

Decision-making involves frontolimbic and dopaminergic brain regions, but how prior choice outcomes, dopamine neurotransmission, and frontostriatal activity are integrated to affect choices is unclear. We tested 60 healthy volunteers using the Balloon Analogue Risk Task (BART) during functional magnetic resonance imaging. In the BART, participants can pump virtual balloons to increase potential...

The magnitude and pattern of motor responses to single doses of subcutaneous apomorphine and oral levodopa were compared in 14 patients with Parkinson's disease. Although apomorphine produced much shorter motor responses than levodopa, the quality of response to the two drugs was virtually indistinguishable. These clinical observations support the notion that integrity of striatal post-synaptic...

Levodopa-induced dyskinesias (LID) belong to the most common dose-limiting adverse effects of levodopa therapy. "Peak-dose" LID occur with the maximum effect of medication, 'diphasic dyskinesias' have a "beginning- and end-of-dose" pattern, and the, "off-period dyskinesia" occur during off-periods, most frequently in the early mornings and are typically dystonic in nature. The majority of patie...

Calcium entry blockers such as felodipine induce natriuresis without a parallel rise of potassium excretion. Previous studies with exogenous aldosterone and felodipine have suggested that the absence of kaliuresis might be explained by a felodipine-induced inhibition of aldosterone release. The natriuresis with calcium entry blockers could not be attributed to a similar mechanism but might be d...

This review summarizes published results that are related to the coupling between the dopaminergic and the serotonergic systems and their association to Parkinson’s disease. We focus on the 6-hydroxydopamine rat model of Parkinson’s disease to better understand how dopamine dysfunction affects the serotonergic system, and furthermore to investigate whether a bidirectional coupling exists and ho...

Midbrain dopaminergic neurons maintain low ongoing "tonic" activity interrupted by high frequency bursts associated with behavioral reward. Dopamine released during bursts feeds back onto D(2) autoreceptors that depress neuronal activity. New findings from Ingram and colleagues suggest that, by contrast, tonic activity excites these neurons by activating an uncoupled Cl- conductance that is med...