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Happiness is key for both mental and physical well-being. To further understand the brain mechanisms involved, we utilized the cataplexy that occurs in narcoleptic animal models as a quantitative behavioral measure because it is triggered by actions associated with happiness, such as laughter in humans and palatable foods in mice. Here we report that the rostral part of the nucleus accumbens (NAc) shell is strongly activated during the beginning of chocolate-induced cataplexy in orexin neuron-ablated mice. We made a local lesion in the NAc using ibotenic acid and observed the animals' behavior. The number of cataplexy bouts was negatively correlated to the lesion size. We also examined the hedonic response to palatable food by measuring the number of tongue protrusions in response to presentation of honey, which was also found to be negatively correlated to the lesion size. Next, we used clozapine N-oxide to either activate or inactivate the NAc through viral DREADD expression. As expected, the number of cataplexy bouts increased with activation and decreased with inactivation, and saline control injections showed no changes. Hedonic response in the DREADD experiment varied and showed both increases and decreases across mice. These results demonstrated that the rostral part of the NAc plays a crucial role in triggering cataplexy and hedonic orofacial movements. Since the NAc is also implicated in motivated behavior, we propose that the NAc is one of the key brain structures involved in happiness and is a driving force for positive emotion-related behaviors. [ABSTRACT FROM AUTHOR]

A novel structure composed of TiO nanowire arrays (NWAs) was designed and synthesized by decorating with graphene-linked graphitic carbon nitride (GCN) layers. It serves as a robust photoanode for high-performance solar-driven water splitting in an alkaline solution. The GCN layers were deposited on TiO NWAs by a facile electrophoretic method, producing an interconnected two-dimensional GCN nanosheets/one-dimensional TiO NWAs heterostructure. Under simulated solar light illumination (light intensity 100 mW cm), the optimal GCN/TiO NWAs photoelectrode produces a photocurrent density of 1.7 mA cm at 1.23 V versus reversible hydrogen electrode (RHE), which is around 2.6 times enhancement from that of pristine TiO (0.7 mA cm at 1.23 V vs. RHE). The photo-conversion efficiency of GCN/TiO NWAs is up to 0.92 % at a low bias potential 0.50 V versus RHE, 3.6 times higher than pristine TiO (0.27 % at 0.59 V vs. RHE). The improved photoelectrochemical activity is mainly because of the improved charge separation and transport within the heterojunction as well as enhanced light absorption. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]