Adam Weitemier

The urocortin 1 neurocircuit: ethanol-sensitivity and potential involvement in alcohol consumption.

One of the hallmarks of alcoholism is continued excessive consumption of alcohol-containing beverages despite the negative consequences of such behavior. The neurocircuitry regulating alcohol consumption is not well understood. Recent studies have shown that the neuropeptide urocortin 1 (Ucn1), a member of the corticotropin-releasing factor (CRF) family of peptides, could be an important player in the regulation of alcohol consumption. This evidence is accumulated along three directions of research: (1) Ucn 1-containing neurons are extremely sensitive to alcohol; (2) the Ucn1 neurocircuit may contribute to the genetic predisposition to high alcohol intake in mice and rats; (3) manipulation of the Ucn1 system alters alcohol consumption and sensitivity. This paper reviews the current knowledge of the Ucn1 neurocircuit and the evidence for its involvement in alcohol-related behaviors, and proposes a mechanism for its involvement in the regulation of alcohol consumption.

Near-infrared deep brain stimulation via upconversion nanoparticle–mediated optogenetics

Stimulating deep inside the brain Noninvasive deep brain stimulation is an important goal in neuroscience and neuroengineering. Optogenetics normally requires the use of a blue laser inserted into the brain. Chen et al. used specialized nanoparticles that can upconvert near-infrared light from outside the brain into the local emission of blue light (see the Perspective by Feliu et al.). They injected these nanoparticles into the ventral tegmental area of the mouse brain and activated channelrhodopsin expressed in dopaminergic neurons with near-infrared light generated outside the skull at a distance of several millimeters. This technique allowed distant near-infrared light to evoke fast increases in dopamine release. The method was also used successfully to evoke fear memories in the dentate gyrus during fear conditioning. Science, this issue p. 679; see also p. 633 Optogenetic experiments can be performed inside the mouse brain by using near-infrared light applied outside the skull. Optogenetics has revolutionized the experimental interrogation of neural circuits and holds promise for the treatment of neurological disorders. It is limited, however, because visible light cannot penetrate deep inside brain tissue. Upconversion nanoparticles (UCNPs) absorb tissue-penetrating near-infrared (NIR) light and emit wavelength-specific visible light. Here, we demonstrate that molecularly tailored UCNPs can serve as optogenetic actuators of transcranial NIR light to stimulate deep brain neurons. Transcranial NIR UCNP-mediated optogenetics evoked dopamine release from genetically tagged neurons in the ventral tegmental area, induced brain oscillations through activation of inhibitory neurons in the medial septum, silenced seizure by inhibition of hippocampal excitatory cells, and triggered memory recall. UCNP technology will enable less-invasive optical neuronal activity manipulation with the potential for remote therapy.

Phasic reward responses in the monkey striatum as detected by voltammetry with diamond microelectrodes

Reward-induced burst firing of dopaminergic neurons has mainly been studied in the primate midbrain. Voltammetry allows high-speed detection of dopamine release in the projection area. Although voltammetry has revealed presynaptic modulation of dopamine release in the striatum, to date, reward-induced release in awakened brains has been recorded only in rodents. To make such recordings, it is possible to use conventional carbon fibres in monkey brains but the use of these fibres is limited by their physical fragility. In this study, constant-potential amperometry was applied to novel diamond microelectrodes for high-speed detection of dopamine. In primate brains during Pavlovian cue-reward trials, a sharp response to a reward cue was detected in the caudate of Japanese monkeys. Overall, this method allows measurements of monoamine release in specific target areas of large brains, the findings from which will expand the knowledge of reward responses obtained by unit recordings.

Accumbal dopamine and serotonin activity throughout acquisition and expression of place conditioning: correlative relationships with preference and aversion.

The ability of addictive drugs to induce adaptations in mesolimbic dopamine (DA) activity offers an attractive neurobiological explanation for enhanced incentive motivation toward drug‐associated stimuli in addiction. However, direct evidence supporting this is sparse. By tracking neurochemical activity within the mouse nucleus accumbens via microdialysis during repeated pairing of morphine with environmental stimuli, we reveal a predictive relationship between enhanced DA responses to morphine and subsequent preference towards a morphine‐paired stimulus. A similar relationship for serotonin (5‐HT) was observed, suggesting that these neuromodulatory systems work in concert. During expression of preference towards a morphine‐paired stimulus, extracellular DA was not enhanced but was negatively associated with this behavior on a subject‐by‐subject basis. In contrast, avoidance of an aversively‐paired stimulus (the opiate antagonist naloxone) was associated with enhanced extracellular DA levels, and also the balance between DA and 5‐HT responses. These findings reveal a tangible predictive relationship between drug‐induced neural adaptations and conditioned behavior, and emphasize that DA activity is not generalized to all subcomponents of behavior conditioned by addictive drugs. They further provide evidence for an active role of DA–5‐HT interactions in the expression of learned behavior.

Reward-Induced Phasic Dopamine Release in the Monkey Ventral Striatum and Putamen.

In-vivo voltammetry has successfully been used to detect dopamine release in rodent brains, but its application to monkeys has been limited. We have previously detected dopamine release in the caudate of behaving Japanese monkeys using diamond microelectrodes (Yoshimi 2011); however it is not known whether the release pattern is the same in various areas of the forebrain. Recent studies have suggested variations in the dopaminergic projections to forebrain areas. In the present study, we attempted simultaneous recording at two locations in the striatum, using fast-scan cyclic voltammetry (FSCV) on carbon fibers, which has been widely used in rodents. Responses to unpredicted food and liquid rewards were detected repeatedly. The response to the liquid reward after conditioned stimuli was enhanced after switching the prediction cue. These characteristics were generally similar between the ventral striatum and the putamen. Overall, the technical application of FSCV recording in multiple locations was successful in behaving primates, and further voltammetric recordings in multiple locations will expand our knowledge of dopamine reward responses.

Temporal Differentiation of pH-Dependent Capacitive Current from Dopamine

Voltammetric recording of dopamine (DA) with fast-scan cyclic voltammetry (FSCV) on carbon fiber microelectrodes have been widely used, because of its high sensitivity to dopamine. However, since an electric double layer on a carbon fiber surface in a physiological ionic solution behaves as a capacitor, fast voltage manipulation in FSCV induces large capacitive current. The faradic current from oxidation/reduction of target chemicals must be extracted from this large background current. It is known that ionic shifts, including H(+), influence this capacitance, and pH shift can cause confounding influences on the FSCV recordings within a wide range of voltage. Besides FSCV with a triangular waveform, we have been using rectangular pulse voltammetry (RPV) for dopamine detection in the brain. In this method, the onset of a single pulse causes a large capacitive current, but unlike FSCV, the capacitive current is restricted to a narrow temporal window of just after pulse onset (<5 ms). In contrast, the peak of faradic current from dopamine oxidation occurs after a delay of more than a few milliseconds. Taking advantage of the temporal difference, we show that RPV could distinguish dopamine from pH shifts clearly and easily. In addition, the early onset current was useful to evaluate pH shifts. The narrow voltage window of our RPV pulse allowed a clear differentiation of dopamine and serotonin (5-HT), as we have shown previously. Additional recording with RPV, alongside FSCV, would improve identification of chemicals such as dopamine, pH, and 5-HT.

A dopaminergic switch for fear to safety transitions

Overcoming aversive emotional memories requires neural systems that detect when fear responses are no longer appropriatexa0so that they can be extinguished. The midbrain ventral tegmental area (VTA) dopamine system has been implicated in reward and more broadly in signaling when a better-than-expected outcome has occurred. This suggests that it may be important in guiding fear to safety transitions. We report that when an expected aversive outcome does not occur, activity in midbrain dopamine neurons is necessary to extinguish behavioral fear responses and engage molecular signaling events in extinction learning circuits. Furthermore, a specific dopamine projection to the nucleus accumbens medial shell is partially responsible for this effect. In contrast, a separate dopamine projection to the medial prefrontal cortex opposes extinction learning. This demonstrates a novel function for the canonical VTA-dopamine reward system and reveals opposing behavioral roles for different dopamine neuron projections in fear extinction learning.Fear memories are overcome only when it is ascertained that fearful responses are not appropriate. Here the authors demonstrate that activity in dopamine neurons is necessary to extinguish fear responses and two distinct dopamine neuron projections exert opposing effects on extinction learning.

Noradrenergic modulation of evoked dopamine release and pH shift in the mouse dorsal hippocampus and ventral striatum

Rapid monoamine release in the dorsal hippocampus is not well characterized, despite its postulated role in modulating fast hippocampal circuit dynamics. We measured monoamine release in the dorsal hippocampus upon stimulation of the ventral tegmental area (VTA) with fast-scan cyclic voltammetry in anesthetized norepinephrine-depleted and non-depleted mice. Within the hippocampus, norepinephrine depletion altered the ability of α2 adrenergic compounds and transporter blockers to modulate the small, evoked monoamine signal. These manipulations also affected the pH shifts observed after stimulation in a drug-dependent manner. The evoked signal was potentiated by α2C adrenoceptor subtype antagonism, but was not affected by or α2A adrenoceptor antagonism. The same subtype-specific pattern was observed on evoked dopamine release in the ventral striatum. The pharmacological and anatomical evidence supports a contribution by dopamine to the VTA-evoked hippocampal monoamine signal, and confirms the interaction between the mesohippocampal and coeruleohippocampal systems. These results also reinforce the notion that α2C, but not α2A adrenoceptors regulate endogenous dopaminergic activity. We believe our findings hold implications for understanding the efficacy of α2 adrenergic agonists and antagonists that are used widely for therapeutic purposes.

Catecholamine activity during drug conditioned place preference and aversion

s / Neuroscience Research 58S (2007) S1–S244 S177 P2-j0 5 Effects of low power laser irradiation on muscle contraction of the frog gastrocnemius Shinichi Kogure, Noriko Ebisu, Tomihiro Kubo, Yoshiki Matsuda Department of Bioinformatics, Soka University, Tokyo, Japan Since laser irradiation could block the generation of anode-breakexcitation in frog sciatic nerve, we examined effects of laser irradiation on contraction of the gastrocnemius. Nineteen frogs (Xenopus laevis) were used and their gastrocnemius muscle with sciatic nerve was prepared. Muscle tension continuously induced by a supramaximal stimulus to the sciatic nerve at 1/s for 12 min gradually attenuated. Direct irradiation of laser (Nd:YVO4, 532 nm, 180 mW) to the muscle surface (28.3 mm2) during the stimulating significantly retarded its attenuation (p < 0.01). Half time defined as duration between maximum and half amplitude in tension showed a declining tendency with increasing of frog weight. Laser irradiation made its slope more gradually. When the rest period for 2 min was set between stimulating sessions and the laser irradiation was applied during the rest period, the attenuation was also retarded by laser irradiation (p < 0.05). It is suggested that laser irradiation influences transmission at neuromuscular junction and excitation–contraction coupling. Research fund: MEXT HAITEKU (2004-08) P2-j0 6 Nitric oxide production results in disuse-induced muscle atrophy through dislocation of neuronal nitric oxide synthase Naoki Suzuki1, Norio Motohashi2, Yuko Suzuki2, Yasuto Itoyama1, Masashi Aoki1, Shin’ichi Takeda2 1 Department of Neurology, Tohoku University School of Medicine, Sendai, Japan; 2 Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan To elucidate the mechanism of muscle atrophy, we analyzed the expression of dystrophin glycoprotein complex (DGC) members during tail suspension, a model of unloading-induced muscle atrophy. Neuronal nitric oxide synthase (nNOS) quickly disappeared from the sarcolemma to the cytoplasm and produce NO during tail suspension. nNOS-null mice showed much milder muscle atrophy than wild-type mice. Nuclear accumulation of de-phosphorylated Foxo3a was not evident in nNOS-null muscle, together with the lack of up-regulation of the muscle-specific E3ubiquitin-ligases. We conclude that nNOS/NO mediates muscle atrophy via regulation of Foxo transcription factors. Research fund: H18-kokoro-019, 17590857, 18590392 P2-j0 8 Role of the zinc-finger transcriptional factor Gli3 in determining striatal structure and striatal-based behavior Kazuto Sakoori1, Motoyama Jun2, Niall Murphy1 1 Murphy Research Unit, BSI, RIKEN, Saitama, Japan; 2 Motoyama Research Unit, BSI, RIKEN, Saitama, Japan The striatum is the largest component of the basal ganglia circuit and plays important roles in motor, cognitive, and emotional functions. The lateral and medial ganglionic eminence is a major source of striatal cells during development. Gli3 is a repressor of vertebrate Hedgehog signaling and is critical in determining the ventral-dorsal patterning of the telencephalon. In the homozygous embryos of Extra-toes mice, which carry a deletion in the Gli3 gene, the ventral telencephalon is expanded. We hypothesized that Gli3 may have an important role in the development of the striatum. We found abnormal striatal structure (increased volume and reduced number of cholinergic interneurons) and abnormal striatal-based behavior (enhanced locomotor response, sensitization and place preference to methamphetamine) in adult heterozygous extra-toes mouse. These results indicate that Gli3 plays an important role in the development of the striatum and sheds light on the relationship between the morphology of striatum and sensitivity to drugs. P2-j0 9 Frontal lobe function in eating disorder: A multichannel near-infrared spectroscopy study Masashi Suda, Toru Uehara, Makoto Ito, Toshimasa Sato, Masato Fukuda, Masahiko Mikuni Department of Psychiatry and Human Behavior, Gunma University, Gunma, Japan Background: Functional neuroimaging has been employed for eating disorder (ED) only in several studies. Completely noninvasive nature and natural setting for measurement of near-infrared spectroscopy (NIRS) is suitable for neuroimaging analyses of ED pathophysiology. Materials and methods: Oxygenated hemoglobin concentration ([oxy-Hb]) changes were monitored during a verbal fluency task using a multichannel NIRS (Hitachi Medical, ETG-4000) in 18 ED patients, and their correlations with clinical symptoms assessed with the Eating Attitude Scale (EAT26) were examined. Results: [oxy-Hb] increases were smaller in the ED group, especially in right fronto-temporal areas, and negatively correlated with dieting tendency scores of the EAT-26 in right fronto-temporal areas and with restriction of eating and binge eating scores in left frontal areas, but not with body mass index. Conclusion: Pathophysiology of ED is considered to consist of dieting tendency and eating behavior problems mediated by right frontal and left frontal cortex, respectively. P2-j10 A new model to evaluate affective states associated with reward-predicting cues in mice Barbara Cagniard, Niall P. Murphy Neuronal Circuit Mechanisms Research Group, RIKEN Brain Science Institute, Wako-shi, Japan The main obstacle to treating addiction is relapse, i.e. restoration of reward intake. Relapse can be precipitated by environmental cues previously associated with reward. Little research has been performed on affective states resulting from presentation of cues predicting reward and their role in creating, maintaining and restoring addiction. To investigate this, we adapted to mice the taste reactivity paradigm; a procedure to assess affective states. We coupled this to a procedure for inducing anticipation of reward that consisted of repeatedly presenting food to mice in a testing cage 30 min after introduction. Taste reactivity was recorded at different phases of the development and extinction of anticipatory behavior. In food-deprived, but not food-sated mice, an anticipatory activity progressively developed that extinguished when food was no longer presented. Analysis of taste reactivity is in progress. This novel model should greatly aid in understanding how affective states change during the transition to addiction, and their underlying neurobiology. P2-j11 Catecholamine activity during drug conditioned place preference and aversion Adam Z. Weitemier, Niall P. Murphy RIKEN BSI, Japan In conditioned place preference (CPP), distinct environments are paired independently with either vehicle, or a rewarding drug. After conditioning, animals will bias their exposure to the drug-paired environment when presented with both at once. CPP demonstrates the unique way that addictive drugs are able to influence learning because the drug CPP involves volitional control of behavior (i.e. choice) although animals do not learn any instrumental actions directed at obtaining drug. In this way, it may represent the most fundamental processes involved in drug seeking behavior during addiction. Still, the neural mechanisms underlying learning and memory during CPP remain poorly understood. To yield neurobiological data directly related to this behavior, we measured neurochemical activity via microdialysis during the acquisition and expression of CPP. Here we show extracellular levels of dopamine and serotonin within the nucleus accumbens during the acquisition and expression of morphine CPP and naloxone CPA (e.g. conditioned place aversion). The results will be discussed in light of the involvement of catecholamines in reward-seeking behavior and learning.