To clarify if dopamine (DA) synthesis is regulated by D-1 DA receptors located on dopaminergic nerve terminals in the striatum, we investigated effects of D-1 DA receptor agonist and antagonist on striatal 3,4-dihydroxyphenylalanine (DOPA) accumulation induced by gamma-butyrolactone in mice treated with an amino acid decarboxylase inhibitor. SKF 38393, a D-1 agonist, did not affect DOPA accumul...

The authors have recently shown that attenuation of an external response feedback leads to excessive lever-pressing that is not associated with attempts to collect reward, and they have suggested that this may be an analogue to "unreasonable" excessive behavior characteristic of obsessive-compulsive disorder. The present study shows that repeated administration of SCH 23390 or quinpirole, but n...

Receptive fields of gap junction-coupled axon terminals of B-type horizontal cells of isolated rabbit retinae were measured by recording light responses to slit shaped light stimuli at different eccentricities from the recording site. The D1/D5 agonist SKF-38393 and the membrane permeant second messenger 8-bromo-cAMP caused decreases of space constants by 20% while the D1/D5 antagonist SCH-2339...

One of the current hypotheses on dopamine in the physiology of motivation posits that this neurotransmitter regulates filtering and selection of inputs to the nucleus accumbens. The effects of dopamine (100 microM) and the D1-receptor agonist SKF 38393 (20-50 microM) on GABAergic synaptic transmission between pairs of principal cells of rat nucleus accumbens were studied by using simultaneous d...

Reduction of wavelength discrimination ability in the 560-640 nm range, but not in the 404-540 nm range, has been demonstrated in goldfish after intravitreal injection of D1-dopamine receptor antagonists. Intravitreal injection of the dopaminergic neurotoxin 6-OH-dopamine severely reduced wavelength discrimination ability in the 540-661 nm range within 3 days. Discrimination ability could be re...

It is now accepted that dopamine plays an important neuromodulatory role in the central nervous control of respiration. D1, D2 and D4 subtypes of receptor seem to be important players, but the assignment of various respiratory tasks to specific subtypes of dopamine receptor is a work in progress. In the present investigation, dihydrexidine (DHD), a full dopamine receptor agonist with affinity f...

In both primates and rodents, the prefrontal cortex (PFC) is highly innervated by dopaminergic fibers originating from the ventral tegmental area, and activation of this mesocortical dopaminergic system decreases spontaneous and evoked activity in the PFC in vivo. We have examined the effects of dopamine (DA), over a range of concentrations, on the passive and active membrane properties of laye...

The effects of dopamine (DA) on a persistent Na(+) current (I(NaP)) in layer V-VI prefrontal cortical (PFC) pyramidal cells were studied using whole cell voltage-clamp recordings in rat PFC slices. After blocking K(+) and Ca (2+) currents, a tetrodotoxin-sensitive I(NaP) was activated by slow depolarizing voltage ramps or voltage steps. DA modulated the I(NaP) in a voltage-dependent manner: inc...