Dopamine presynaptically and heterogeneously modulates nucleus accumbens medium-spiny neuron GABA synapses in vitro

BACKGROUND: The striatal complex is the major target of dopamine action in the CNS. There, medium-spiny GABAergic neurons, which constitute about 95% of the neurons in the area, form a mutually inhibitory synaptic network that is modulated by dopamine. When put in culture, the neurons reestablish this network. In particular, they make autaptic connections that provide access to single, identified medium-spiny to medium-spiny neuron synaptic connections. RESULTS: We examined medium-spiny neuron autaptic connections in postnatal cultures from the nucleus accumbens, the ventral part of the striatal complex. These connections were subject to presynaptic dopamine modulation. D1-like receptors mediated either inhibition or facilitation, while D2-like receptors predominantly mediated inhibition. Many connections showed both D1 and D2 modulation, consistent with a significant functional colocalization of D1 and D2-like receptors at presynaptic sites. These same connections were subject to GABA(A), GABA(B), norepinephrine and serotonin modulation, revealing a multiplicity of modulatory autoreceptors and heteroreceptors on individual varicosities. In some instances, autaptic connections had two components that were differentially modulated by dopamine agonists, suggesting that dopamine receptors could be distributed heterogeneously on the presynaptic varicosities making up a single synaptic (i.e. autaptic) connection. CONCLUSION: Differential trafficking of dopamine receptors to different presynaptic varicosities could explain the many controversial studies reporting widely varying degrees of dopamine receptor colocalization in medium-spiny neurons, as well as more generally the diversity of dopamine actions in target areas. Longer-term changes in the modulatory actions of dopamine in the striatal complex could be due to plasticity in the presynaptic distribution of dopamine receptors on medium-spiny neuron varicosities

Renal Artery Embolism: A Case Report and Review

Renal artery embolism was first described in 1940, but it is only recently becoming recognized as a clinically significant entity. Although relatively uncommon, it is clearly responsible for considerable morbidity in patients who experience it. The pathogenesis is typically related to cardiac thrombus formation with subsequent embolization, although other etiologies have been described. The authors present a case report followed by a review of the literature to highlight the clinical characteristics of this phenomena. Presentation, diagnostics, and treatment options will be reviewed with the aim of increasing awareness of renal artery embolism. As clinicians become more familiar with this condition, they will be more likely to consider it as a possible diagnosis in patients with a typical presentation. This will hopefully lead to improved care through prompt diagnosis and treatment, particularly as one treatment option may be time sensitive