3-Carene, a Phytoncide from Pine Tree Has a Sleep-enhancing Effect by Targeting the GABA(A)-benzodiazepine Receptors

3-Carene, a bicyclic monoterpene, is one of the major components of the pine tree essential oils. It has been reported that, in addition to its known properties as a phytoncide, 3-carene has anti-inflammatory, antimicrobial, and anxiolytic effects. We have previously demonstrated that α-pinene, the major component of pine tree, has a hypnotic effect through GABA(A)-benzodiazepine (BZD) receptors. However, a hypnotic effect of 3-carene has not been studied yet. Here, we report that oral administration of 3-carene increases the sleep duration and reduces sleep latency in pentobarbital-induced sleep test. 3-Carene potentiates the GABA(A) receptor-mediated synaptic responses by prolonging the decay time constant of inhibitory synaptic responses. These enhancing effects of 3-carene are reproduced by zolpidem, a modulator for GABA(A)-BZD receptor, and fully inhibited by flumazenil, an antagonist for GABA(A)-BZD receptor. The molecular docking of 3-carene to the BZD site of GABA(A) protein structure, suggests that 3-carene binds to the BZD site of α1 and ϒ2 subunits of GABA(A)-BZD receptor. These results indicate that, similar to α-pinene, 3-carene shows a sleep-enhancing effect by acting as a positive modulator for GABA(A)-BZD receptor.

Gait Ignition Failure in JNPL3 Human Tau-mutant Mice

Cognitive impairments and motor dysfunction are commonly observed behavioral phenotypes in genetic animal models of neurodegenerative diseases. JNPL3 transgenic mice expressing human P301L-mutant tau display motor disturbances with age- and gene dose-dependent development of neurofibrillary tangles, suggesting that tau pathology causes neurodegeneration associated with motor behavioral abnormalities. Although gait ignition failure (GIF), a syndrome marked by difficulty in initiating locomotion, has been described in patients with certain forms of tauopathies, transgenic mouse models mirroring human GIF syndrome have yet to be reported. Using the open field and balance beam tests, here we discovered that JNPL3 homozygous mice exhibit a marked delay of movement initiation. The elevated plus maze excluded the possibility that hesitation to start in JNPL3 mice was caused by enhanced levels of anxiety. Considering the normal gait ignition in rTg4510 mice expressing the same mutant tau in the forebrain, GIF in JNPL3 mice seems to arise from abnormal tau deposition in the hindbrain areas involved in locomotor initiation. Accordingly, immunohistochemistry revealed highly phosphorylated paired helical filament tau in JNPL3 brainstem areas associated with gait initiation. Together, these findings demonstrate a novel behavioral phenotype of impaired gait initiation in JNPL3 mice and underscore the value of this mouse line as a tool to study the neural mechanisms and potential treatments for human GIF syndrome.