Molecular chaperones and the ubiquitin-proteasome system are participants in the defense against unfolded proteins and provide an effective protein quality control system that is essential for cellular functions and survival. Ubiquitinated tau-positive inclusion bodies containing the small heat shock protein αB-crystallin in oligodendrocytes are consistent features of a variety of neurodegenerative diseases, and defects in the proteasome system might contribute to the aggregation process. Oligodendrocytes, the myelin-forming cells of the CNS, are specifically sensitive to stress situations. Here we can show that in cultured rat brain oligodendrocytes proteasomal inhibition by MG-132 or lactacystin caused apoptotic cell death and the induction of heat shock proteins in a time- and concentration-dependent manner. Specifically, αB-crystallin was upregulated, and ubiquitinated proteins accumulated. After incubation with MG-132 the tau was dephosphorylated, which enhanced its microtubule-binding capacity. Prote...

We examined patterns of neural activity as assayed by changes in gene expression to localize representation of acoustic mating signals in the auditory midbrain of frogs. We exposed wild-caught male Physalaemus pustulosus to conspecific mating calls that vary in their behavioral salience, nonsalient mating calls, or no sound. We measured expression of the immediate early gene egr-1 (also called ZENK, zif 268, NGFI -A, and krox -24) throughout the torus semicircularis, the auditory midbrain homolog of the inferior colliculus. Differential egr-1 induction in response to the acoustic stimuli occurred in the laminar, midline, and principal nuclei of the torus semicircularis, whereas the ventral region did not show significant effects of stimulus. The laminar nucleus differentially responded to conspecific mating calls compared with nonsalient mating calls, whereas the midline and principal nuclei responded preferentially to one of two conspecific calls. These responses were not explained by simple acoustic prop...

Gephyrin is an essential component of the postsynaptic cortical protein network of inhibitory synapses. Gephyrin-based scaffolds participate in the assembly as well as the dynamics of receptor clusters by connecting the cytoplasmic domains of glycine and GABAA receptor polypeptides to two cytoskeletal systems, microtubules and microfilaments. Although there is evidence for a physical linkage between gephyrin and microtubules, the interaction between gephyrin and microfilaments is not well understood so far. Here, we show that neuronal gephyrin interacts directly with key regulators of microfilament dynamics, profilin I and neuronal profilin IIa, and with microfilament adaptors of the mammalian enabled (Mena)/vasodilator stimulated phosphoprotein (VASP) family, including neuronal Mena. Profilin and Mena/VASP coprecipitate with gephyrin from tissue and cells, and complex formation requires the E-domain of gephyrin, not the proline-rich central domain. Consequently, gephyrin is not a ligand for the proline-bi...

Endocannabinoid signaling couples activity-dependent rises in postsynaptic Ca2+ levels to decreased presynaptic GABA release. Here, we present evidence from paired recording experiments that cannabinoid-mediated inhibition of GABA release depends on the firing rates of the presynaptic interneurons. Low-frequency action potentials in post hoc identified cholecystokinin-positive CA1 basket cells elicited IPSCs in the postsynaptic pyramidal cells that, as expected, were fully abolished by the exogenous application of the cannabinoid receptor agonist WIN55,212-2 [ R -(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrol[1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate] at 5 μm. However, the presynaptic basket cells recovered from the cannabinoid agonist-induced inhibition of GABA release when the presynaptic firing rate was increased to ≥20 Hz. Pharmacological experiments showed that the recovered transmission was exclusively dependent on presynaptic N-type Ca2+ channels. Furthe...

Ca2+/calmodulin-dependent kinases (CaMKs) are essential for neuronal development and plasticity, processes requiring de novo protein synthesis. Roles for CaMKs in modulating gene transcription are well established, but their involvement in mRNA translation is evolving. Here we report that activity-dependent translational initiation in cultured rat hippocampal neurons is enhanced by CaMKI-mediated phosphorylation of Ser1156 in eukaryotic initiation factor eIF4GII (4GII). Treatment with bicuculline or gabazine to enhance neuronal activity promotes recruitment of wild-type 4GII, but not the 4GII S1156A mutant or 4GI, to the heterotrimeric eIF4F (4F) complex that assembles at the 5′ cap structure (m7GTP) of mRNA to initiate ribosomal scanning. Recruitment of 4GII to 4F is suppressed by pharmacological inhibition (STO-609) of CaM kinase kinase, the upstream activator of CaMKI. Post hoc in vitro CaMKI phosphorylation assays confirm that activity promotes phosphorylation of S1156 in transfected 4GII in neurons. C...

It has been suggested that anandamide ( N -arachidonoylethanolamine), an endogenous cannabinoid substance, may be produced through Ca2+-stimulated hydrolysis of the phosphatidylethanolamine (PE) derivative N -arachidonoyl PE. The presence of N -arachidonoyl PE in adult brain tissue and the enzyme pathways that underlie its biosynthesis are, however, still undetermined. We report here that rat brain tissue contains both anandamide (11 ± 7 pmol/gm wet tissue) and N -arachidonoyl PE (22 ± 16 pmol/gm), as assessed by gas chromatography/mass spectrometry. We describe a N -acyltransferase activity in brain that catalyzes the biosynthesis of N -arachidonoyl PE by transferring an arachidonate group from the sn -1 carbon of phospholipids to the amino group of PE. We also show that sn -1 arachidonoyl phospholipids are present in brain, where they constitute ∼0.5% of total phospholipids. N -acyltransferase activity is Ca2+ dependent and is enriched in brain and testis. Within the brain, N -acyltransferase activity is...

Dopaminergic drugs affect a variety of cognitive processes, but the direction and extent of effects vary across individuals and tasks. Paradoxical effects are observed, by which the same drug causes cognitive enhancing as well as adverse effects. Here, we demonstrate that individual differences in impulsive personality account for the contrasting effects of dopaminergic drugs on working memory and associated frontostriatal activity. We observed that the dopamine D2 receptor agonist bromocriptine improved the flexible updating (switching) of relevant information in working memory in high-impulsive subjects, but not in low-impulsive subjects. These behavioral effects in high-impulsive subjects accompanied dissociable effects on frontostriatal activity. Bromocriptine modulated the striatum during switching but not during distraction from relevant information in working memory. Conversely, the lateral frontal cortex was modulated by bromocriptine during distraction but not during switching. The present results...

Voltage-gated calcium channel Cav2.1 undergoes Ca2+-dependent facilitation and inactivation, which are important in short-term synaptic plasticity. In presynaptic terminals, Cav2.1 forms large protein complexes that include synaptotagmins. Synaptotagmin-7 (Syt-7) is essential to mediate short-term synaptic plasticity in many synapses. Here, based on evidence that Cav2.1 and Syt-7 are both required for short-term synaptic facilitation, we investigated the direct interaction of Syt-7 with Cav2.1 and probed its regulation of Cav2.1 function. We found that Syt-7 binds specifically to the α1A subunit of Cav2.1 through interaction with the synaptic-protein interaction (synprint) site. Surprisingly, this interaction enhances facilitation in paired-pulse protocols and accelerates the onset of facilitation. Syt-7α induces a depolarizing shift in the voltage dependence of activation of Cav2.1 and slows Ca2+-dependent inactivation, whereas Syt-7β and Syt-7γ have smaller effects. Our results identify an unexpected, is...

Methamphetamine and methcathinone are psychostimulant drugs with high potential for abuse. In animals, methamphetamine and related drugs are known to damage brain dopamine (DA) neurons, and this damage has recently been shown to be detectable in living nonhuman primates by means of positron emission tomography (PET) with [11C]WIN-35,428, a DA transporter (DAT) ligand. The present studies determined whether living humans with a history of methamphetamine or methcathinone abuse showed evidence of lasting decrements in brain DAT density. PET studies were performed in 10 control subjects, six abstinent methamphetamine users, four abstinent methcathinone users, and three patients with Parkinson’s disease (PD). On average, subjects had abstained from amphetamine use for ∼3 years. Before PET studies, all subjects underwent urine and blood toxicology screens to rule out recent drug use. Compared with controls, abstinent methamphetamine and methcathinone users had significant decreases in DAT density in the caudate...

Relapse is a widely recognized and difficult to treat feature of the addictions. Substantial evidence implicates cue-triggered activation of the mesolimbic dopamine system as an important contributing factor. Even drug cues presented outside of conscious awareness (i.e., subliminally) produce robust activation within this circuitry, indicating the sensitivity and vulnerability of the brain to potentially problematic reward signals. Because pharmacological agents that prevent these early cue-induced responses could play an important role in relapse prevention, we examined whether baclofen—a GABAB receptor agonist that reduces mesolimbic dopamine release and conditioned drug responses in laboratory animals—could inhibit mesolimbic activation elicited by subliminal cocaine cues in cocaine-dependent individuals. Twenty cocaine-dependent participants were randomized to receive baclofen (60 mg/d; 20 mg t.i.d.) or placebo. Event-related BOLD fMRI and a backward-masking paradigm were used to examine the effects of...