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.
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 new study examines the contribution of DNA methylation to long-term behavioral and morphological changes produced by cocaine exposure or chronic social defeat stress.
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.
Földy et al. find that GABAA receptor–mediated synaptic inputs from murine parvalbumin-expressing basket cells are selectively modulated by the membrane voltage– and intracellular chloride–dependent chloride channel ClC-2. Their data reveal a cell type–specific regulation of intracellular chloride homeostasis in the perisomatic region of hippocampal pyramidal neurons.
The authors find that rat central auditory neurons fire action potentials in a stereotyped pattern of mini-bursts prior to hearing onset and that this pattern is initiated by cochlear hair cells.
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.
The authors report that the voltage-gated K+ channel Kv12.2 regulates firing threshold and excitability in hippocampal pyramidal neurons.
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 find that the homeobox gene Dbx1 controls the fate of glutamatergic neurons in the preBötzinger complex (preBötC) that are indispensable for the generation of the respiratory rhythm. Establishment of commissural connections between the halves of the preBötC, which is critical for synchronous discharge, requires Robo3 expression by these neurons.
The kinase mTOR functions to enhance cell growth in many systems. This study finds that injury reduces mTOR activity in neurons of the corticospinal tract (CST) and that enhancing mTOR activity by inactivation of its negative regulator PTEN substantially increases sprouting and regenerative growth of injured CST neurons.
The authors find that deletion of the immediate-early gene Arc, or inhibition of the transcription factor SRF or its cofactor MAL, blocks the late phase of long-term depression (LTD) in cultured cerebellar Purkinje cells. SRF binding to the Arc promoter was required for the late phase of LTD in this system.
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.
Receptive fields in the developing frog optic tectum are refined under the influence of visual inputs. Richards and colleagues find that these changes require intra-tectal GABAergic transmission. Blockade of GABA signaling increased correlated activity in the tectum. The authors argue that GABA signaling acts to set a low ‘background noise’ of correlated activity that allows relevant spike timing–dependent plasticity to reshape intra-tectal synapses and thereby reshape receptive fields.
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.
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 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 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 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 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.
