The GluN3A subunit of N-methyl-D-aspartate receptors (NMDARs) plays an established role in synapse development, but its contribution to neural circuits in the adult brain is less clear. Recent work has demonstrated that in select cell populations, GluN3A assembles with GluN1 to form GluN1/GluN3A receptors that are insensitive to glutamate and instead serve as functional excitatory glycine receptors (eGlyRs). Our understanding of these eGlyRs, and how they contribute to intrinsic excitability and synaptic communication within relevant networks of the developing and the mature brain, is only beginning to be uncovered. Here, using male and female mice, we demonstrate that GluN3A subunits are enriched in the adult ventral hippocampus (VH), where they localize to synaptic and extrasynaptic sites and can assemble as functional eGlyRs on CA1 pyramidal cells. GluN3A expression was barely detectable in the adult dorsal hippocampus (DH). We also observed a high GluN2B content in the adult VH, characterized by slow NMDAR current decay kinetics and a high sensitivity to the GluN2B-containing NMDAR antagonist ifenprodil. Interestingly, the GluN2B enrichment in the adult VH was dependent on GluN3A as GluN3A deletion accelerated NMDAR decay and reduced ifenprodil sensitivity in the VH, suggesting that GluN3A expression can regulate the balance of conventional NMDAR subunit composition at synaptic sites. Lastly, we found that GluN3A knock-out also enhanced both NMDAR-dependent calcium influx and NMDAR-dependent long-term potentiation in the VH. Together, these data reveal a novel role for GluN3A and eGlyRs in the control of ventral hippocampal circuits in the mature brain.

Low-intensity transcranial focused ultrasound stimulation (TUS) is a novel technique for noninvasive brain stimulation (NIBS). TUS delivered in a theta (5 Hz) burst pattern (tbTUS) induces plasticity in the human primary motor cortex (M1) for 30–60 min, showing promise for therapeutic development. Metaplasticity refers to activity-dependent changes in neural functions governing synaptic plasticity; depotentiation is the reversal of long-term potentiation (LTP) by a subsequent protocol with no effect alone. Metaplasticity can enhance plasticity induction and clinical efficacy of NIBS protocols. In our study, we compared four NIBS protocol combinations to investigate metaplasticity on tbTUS in humans of either sex. We delivered four interventions: (1) sham continuous theta burst stimulation with 150 pulses (cTBS150) followed by real tbTUS (tbTUS only), (2) real cTBS150 followed by sham tbTUS (cTBS only), (3) real cTBS150 followed by real tbTUS (metaplasticity), and (4) real tbTUS followed by real cTBS150 (depotentiation). We measured motor-evoked potential amplitude, short-interval intracortical inhibition, long-interval intracortical inhibition, intracortical facilitation (ICF), and short-interval intracortical facilitation before and up to 90 min after plasticity intervention. Plasticity effects lasted at least 60 min longer when tbTUS was primed with cTBS150 compared with tbTUS alone. Plasticity was abolished when cTBS150 was delivered after tbTUS. cTBS150 alone had no significant effect. No changes in M1 intracortical circuits were observed. Plasticity induction by tbTUS can be modified in manners consistent with homeostatic metaplasticity and depotentiation. This substantiates evidence that tbTUS induces LTP-like processes and suggests that metaplasticity can be harnessed in the therapeutic development of TUS.

Aggression involves both sexually monomorphic and dimorphic actions. How the brain implements these two types of actions is poorly understood. We found that in Drosophila melanogaster, a set of neurons, which we call CL062, previously shown to mediate male aggression also mediate female aggression. These neurons elicit aggression acutely and without the presence of a target. Although the same set of actions is elicited in males and females, the overall behavior is sexually dimorphic. The CL062 neurons do not express fruitless, a gene required for sexual dimorphism in flies, and expressed by most other neurons important for controlling fly aggression. Connectomic analysis in a female electron microscopy dataset suggests that these neurons have limited connections with fruitless expressing neurons that have been shown to be important for aggression and signal to different descending neurons. Thus, CL062 is part of a monomorphic circuit for aggression that functions parallel to the known dimorphic circuits.

A new study from Smithsonian scientists analyzes ant and fungus species, and uncovers the origins of their close partnership

A paleontologist at the Natural History Museum in London chronicles the age of the famous and fascinating massive reptiles

A Smithsonian curator reflects back on the artistic legend, a "Renaissance man" with 28 Grammys to his name, who died Sunday at 91 years old

Written by the former chief historian of NASA, the book examines the evolution of our cosmic understanding—from early civilizations to the present day

FAO Director-General José Graziano da Silva today praised UN Secretary-General Ban Ki Moon for his support in the fight against hunger at a meeting with FAO member countries, the Committee [...]

Representatives of all countries in Latin America and the Caribbean have gathered here this week to agree on the actions needed to definitively eradicate hunger in the region before 2025. [...]

Countries today endorsed a set of wide-reaching guidelines that will boost the already vital [...]

The Director-General opened the session this morning noting that FAO is on the right track, and that its sharpened focus needs to translate to concrete benefits at [...]

Building on previous efforts, the Kingdom of Morocco will offer technical assistance to the Republic of Guinea through a South-South Cooperation Tripartite Agreement signed today at FAO headquarters by FAO [...]

Santiago, Chile- The declaration of the XXI Specialized Meeting on Family Farming of MERCOSUR (REAF, in Spanish) held last week in Argentina, acknowledged the advances promoted by FAO’s Director General, [...]

The Thomson Reuters Foundation, the corporate charity of the world’s biggest news and information providers, is teaming up with the UN Food and Agriculture Organization (FAO) to improve [...]

FAO Director-General José Graziano da Silva will be away from Rome during the next few weeks. During this period he will be involved in a range of [...]

Senior staff at FAO yesterday briefed a delegation of five U.S. Senators on FAO’s work on resilience, nutrition, fisheries, climate change, [...]

Between last week’s Global Dialogue on Family Farming, a visit from President Evo Morales and the 3Full Article