Dopamine (DA) plays a critical role in motor control, addiction and reward-seeking behaviors, and its release dynamics have traditionally been linked to changes in midbrain dopamine neuron activity. Here, we report that selective endogenous cholinergic activation achieved via in vitro optogenetic stimulation of nucleus accumbens (NAc), a terminal field of dopaminergic neurons, elicits real-time DA release. This mechanism occurs via direct actions on DA terminals, does not require changes in neuron firing within the midbrain and is dependent on glutamatergic receptor activity. More importantly, we demonstrate that in vivo selective activation of cholinergic interneurons (CINs) is sufficient to elicit DA release in the NAc. Therefore, the control of accumbal extracellular DA levels by endogenous cholinergic activity results from a complex convergence of neurotransmitter/neuromodulator systems that may ultimately synergize to drive motivated behavior.

A high-throughput, retrovirus-mediated mutagenesis method based on gene trapping in embryonic stem cells was used to identify a novel mouse gene. The human ortholog encodes a transmembrane protein containing five extracellular immunoglobulin-like domains that is structurally related to human NEPHRIN, a protein associated with congenital nephrotic syndrome. Northern analysis revealed wide expression in humans and mice, with highest expression in kidney. Based on similarity to NEPHRIN and abundant expression in kidney, this protein was designated NEPH1 and embryonic stem cells containing the retroviral insertion in the Neph1 locus were used to generate mutant mice. Analysis of kidney RNA from Neph1 ؊/؊ mice showed that the retroviral insertion disrupted expression of Neph1 transcripts. Neph1 ؊/؊ pups were represented at the expected normal Mendelian ratios at 1 to 3 days of age but at only 10% of the expected frequency at 10 to 12 days after birth, suggesting an early postnatal lethality. The Neph1 ؊/؊ animals that survived beyond the first week of life were sickly and small but without edema, and all died between 3 and 8 weeks of age. Proteinuria ranging from 300 to 2,000 mg/dl was present in all Neph1 ؊/؊ mice. Electron microscopy demonstrated NEPH1 expression in glomerular podocytes and revealed effacement of podocyte foot processes in Neph1 ؊/؊ mice. These findings suggest that NEPH1, like NEPHRIN, may play an important role in maintaining the structure of the filtration barrier that prevents proteins from freely entering the glomerular urinary space.NEPHRIN is a transmembrane protein of the immunoglobulin (Ig) superfamily that is expressed by epithelial podocytes of developing glomeruli (13, 17). Congenital nephrotic syndrome of the Finnish type results from mutations in NPHS1, the human gene encoding NEPHRIN, indicating a role for NEPHRIN in maintaining the filtration barrier that prevents proteins from freely entering the glomerular urinary space (6,17). Recent studies localized NEPHRIN to the slit diaphragms that form the junctions between podocyte foot processes interdigitating along the glomerular basement membrane. This and other studies suggest that NEPHRIN proteins extending toward each other from adjacent podocyte foot processes may interdigitate in a zipper-like structure to form the crucial filtration barrier in the slit diaphragm. The eight Ig-like domains of each NEPHRIN protein, which are of the C2 type of Ig domain known to be involved in cell-cell interactions, are thought to provide the homophilic interactions that bind these NEPHRIN proteins together (13, 17).We use a high-throughput mutagenesis method based on gene trapping in embryonic stem (ES) cells that allows automated production of sequence tags from the trapped and mutated genes (20). These ES cell clones are stored in a library called Omnibank, and the sequence tag from the gene trapped in each clone, referred to as the Omnibank sequence tag or OST, is entered into a searchable database. A protein with Ig domains was identified with...

The claustrum is a prominent but ill-defined forebrain structure that has been suggested to integrate multisensory information and perhaps transform percepts into consciousness. The claustrum's shape and vague borders have hampered experimental assessment of its functions. We used matrix-assisted laser desorption ionization-imaging mass spectrometry to reveal a novel protein marker, G-protein gamma2 subunit (Gng2), which is enriched in the claustrum but not adjacent structures of the rat forebrain. The spatial pattern of Gng2 expression suggests key differences from commonly held views of the claustrum's structure. Using anatomical methods, we found that the rat claustrum is present only at striatal levels of the telencephalon and does not extend to frontal cortical territories. Moreover, the claustrum is surrounded on all sides by layer VI insular cortex cells in both the rat and primate. Using these defining characteristics of the claustrum, we found that the claustrum projects to cortical but not to subcortical sites. The definition of the claustrum as a cortical site is considered. The identification of a claustrum-specific protein opens the door to selective molecular lesions and the subsequent evaluation of the role of the claustrum in cognition.

The claustrum is among the most enigmatic of all prominent mammalian brain structures. Since the 19th century, a wealth of data has amassed on this forebrain nucleus. However, much of this data is disparate and contentious; conflicting views regarding the claustrum’s structural definitions and possible functions abound. This review synthesizes historical and recent claustrum studies with the purpose of formulating an acceptable description of its structural properties. Integrating extant anatomical and functional literature with theorized functions of the claustrum, new visions of how this structure may be contributing to cognition and action are discussed.

SUMMARY Cognitive abilities, such as volitional attention, operate under top-down, executive frontal cortical control of hierarchically lower structures. The circuit mechanisms underlying this process are unresolved. The claustrum possesses interconnectivity with many cortical areas and, thus, is hypothesized to orchestrate the cortical mantle for top-down control. Whether the claustrum receives top-down input and how this input may be processed by the claustrum have yet to be formally tested, however. We reveal that a rich anterior cingulate cortex (ACC) input to the claustrum encodes a preparatory top-down information signal on a five-choice response assay that is necessary for optimal task performance. We further show that ACC input monosynaptically targets claustrum inhibitory interneurons and spiny glutamatergic projection neurons, the latter of which amplify ACC input in a manner that is powerfully constrained by claustrum inhibitory microcircuitry. These results demonstrate ACC input to the claustrum is critical for top-down control guiding action.

Altered brain energy homeostasis is a key adaptation occurring in the cocaine-addicted brain, but the effect of cocaine on the fundamental source of energy, mitochondria, is unknown. We demonstrate an increase of dynamin-related protein-1 (Drp1), the mitochondrial fission mediator, in nucleus accumbens (NAc) after repeated cocaine exposure and in cocaine-dependent individuals. Mdivi-1, a demonstrated fission inhibitor, blunts cocaine seeking and locomotor sensitization, while blocking c-Fos induction and excitatory input onto dopamine receptor-1 (D1) containing NAc medium spiny neurons (MSNs). Drp1 and fission promoting Drp1 are increased in D1-MSNs, consistent with increased smaller mitochondria in D1-MSN dendrites after repeated cocaine. Knockdown of Drp1 in D1-MSNs blocks drug seeking after cocaine self-administration, while enhancing the fission promoting Drp1 enhances seeking after long-term abstinence from cocaine. We demonstrate a role for altered mitochondrial fission in the NAc, during early cocaine abstinence, suggesting potential therapeutic treatment of disrupting mitochondrial fission in cocaine addiction.

The claustrum is a telencephalic gray matter structure with various proposed functions, including sensory integration and attentional allocation. Underlying these concepts is the reciprocal connectivity of the claustrum with most, if not all, areas of the cortex. What remains to be elucidated to inform functional hypotheses further is whether a pattern exists in the strength of connectivity between a given cortical area and the claustrum. To this end, we performed a series of retrograde neuronal tract tracer injections into rat cortical areas along the cortical processing hierarchy, from primary sensory and motor to frontal cortices. We observed that the number of claustrocortical projections increased as a function of processing hierarchy; claustrum neurons projecting to primary sensory cortices were scant and restricted in distribution across the claustrum, whereas neurons projecting to the cingulate cortex were densely packed and more evenly distributed throughout the claustrum. This connectivity pattern suggests that the claustrum may preferentially subserve executive functions orches trated by the cingulate cortex.

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