Articles in 2010

The authors use combined electrostimulation, neurophysiology, microinjection and fMRI to show that stimulation of a site in the lateral geniculate nucleus of monkeys increases fMRI signals in regions of primary visual cortex, but suppresses it in retinotopically matched regions of extrastriate cortex. Their results suggest that electrostimulation disrupts cortico-cortical signal propagation by silencing the output of any neocortical area whose afferents are electrically stimulated.

A single exposure to a stressor is known to prime the hypothalamic-pituitary-adrenal axis to subsequent stressors. Kuzmiski et al. show that exposure to a stressor, via a corticotrophin-releasing hormone–dependent depression of postsynaptic NMDA receptors, enables glutamatergic synapses to undergo a short-term potentiation, manifested as an increase in presynaptic release probability.

A recent brouhaha over corporate-sponsored scientific blogs sharing the same platform as those that are editorially independent highlights the need for clearly disclosing any potential conflicts of interest in the blogosphere.

A new study examines the contribution of DNA methylation to long-term behavioral and morphological changes produced by cocaine exposure or chronic social defeat stress.

Two studies in this issue show that the protein MeCP2, which is implicated in Rett syndrome, also critically regulates behavioral responses to psychostimulants. Although the two studies highlight different mechanisms of MeCP2 in regulating these behaviors, both underscore the importance of epigenetic mechanisms in establishing drug addiction.

A study in this issue finds that under conditions of intense activity at specific inhibitory synapses, the voltage gated Cl⁻ channel CIC-2 is vital for allowing efflux of accumulated internal Cl⁻.

An examination of the micro-organization of visual cortex using two-photon calcium imaging provides a new level of insight into retinotopic maps, finding that retinotopy is scrambled on fine scales in mouse primary visual cortex.

The authors find that the ATPase NSF interacts directly with Polo-like kinase 2 (Plk2), an activity-inducible kinase that is known to homeostatically decrease excitatory synapse number and strength. Plk2 disrupts the interaction between NSF and the GluA2 AMPAR subunit in a kinase-independent manner, promoting GluA2 internalization and decreased synaptic AMPAR current.

Neurons of the same molecular type can have substantial differences in intrinsic properties. Here the authors find that intrinsic diversity in the mitral cells of the mouse olfactory bulb decreases the firing correlations between neurons and increases the amount of information that can be transmitted by the neuronal population.

Scholsburg and colleagues show that prolonged inactivation of monoacylglycerol lipase, the principal degradative enzyme for the endocannabinoid 2-arachidonoylglycerol, antagonizes the brain endocannabinoid system. This is manifested as tolerance, impaired plasticity and receptor desensitization; these effects are similar to the effects of prolonged exposure to drugs of abuse.

The mouse retina includes cone photoreceptors optimized for short (S) and medium (M) wavelengths; the difference lies in the expression of S and M opsin. Onishi and colleagues find that, in M cones, thyroid hormone–responsive transcription factors induce expression of the SUMO ligase Pias3, whose activity is necessary for repression of S opsin and expression of M opsin.

The authors report that the immediate-early gene Narp accumulates at excitatory synapses on parvalbumin-expressing interneurons. Narp recruits AMPA receptors at excitatory synapses to rebalance network excitation and inhibition dynamics.

The authors find that the expression of the DNA methyltransferase Dnmt3a in mice is regulated by chronic cocaine and chronic social defeat stress in the nucleus accumbens. Manipulations that block DNA methylation potentiate cocaine reward and cause an antidepressant-like effect.

The authors report that MeCP2, a methyl DNA–binding transcriptional regulator, modulates the response to amphetamine in the nucleus accumbens. Using both acute viral manipulation of MeCP2 in mice and hypomorphic Mecp2 mutant mice, they find that MeCp2 both affects mesolimbocortical circuit development and regulates the responses to psychostimulants.

The authors use in vivo two-photon calcium imaging in the mouse to study the micro-organization of primary visual cortex. They report that fine retinotopy is not preserved and that, though receptive field subregions are likely to be shared among neighboring neurons, this overlap is not associated with increased stimulus-evoked correlations.

The authors implicate the transcriptional repressor methyl CpG–binding protein MeCP2 in cocaine addiction. They report that MeCP2 regulates cocaine intake through microRNA-212 to control cocaine's effects on strital BDNF levels.

The intrinsically photosensitive melanopsin-expressing retinal ganglion neurons are important for nonvisual responses to light, such as circadian photoentrainment. These cells, however, require high light intensities to be activated and it has been unclear how photoentrainment to low light levels works. This study finds that rod photoreceptors are essential to photoentrainment at low and middle light intensities.

AKAP79/150 is a protein scaffold that is thought to position specific kinases and phosphastases in their appropriate synaptic domains. The authors report that AKAP interacts with calcineurin to regulate NMDA receptor–dependent plasticity in rat hippocampal slices.