4-Hydroxybenzaldehyde, One of Constituents from Gastrodiae Rhizoma Augments Pentobarbital-induced Sleeping Behaviors and Non-rapid Eye Movement (NREM) Sleep in Rodents

In the previous experiments, we reported that ethanol extract of Gastrodiae Rhizoma, the dried tuber of Gastrodia ElataBlume (Orchidaceae) increased pentobarbital-induced sleeping behaviors. These experiments were undertaken to know whether 4-hydroxybenzaldehyde (4-HBD), is one of the major compounds of Gastrodiae Rhizoma increases pentobarbital-induced sleeping behaviors and changes sleep architectures via activating GABA(A)-ergic systems in rodents. 4-HBD decreased locomotor activity in mice. 4-HBD increased total sleep time, and decreased of sleep onset by pentobarbital (28 mg/kg and 40 mg/kg). 4-HBD showed synergistic effects with muscimol (a GABA(A) receptor agonist), shortening sleep onset and enhancing sleep time on pentobarbital-induced sleeping behaviors. On the other hand, 4-HBD (200 mg/kg, p.o.) itself significantly inhibited the counts of sleep-wake cycles, and prolonged total sleep time and non-rapid eye movement (NREM) in rats. Moreover, 4-HBD increased intracellular Cl- levels in the primary cultured cerebellar cells. The protein levels of glutamic acid decarboxylase (GAD) and GABA(A) receptors subunits were over-expressed by 4-HBD. Consequently, these results demonstrate that 4-HBD increased NREM sleep as well as sleeping behaviors via the activation of GABA(A)-ergic systems in rodents.

Pachymic Acid Enhances Pentobarbital-Induced Sleeping Behaviors via GABA(A)-ergic Systems in Mice

This study was investigated to know whether pachymic acid (PA), one of the predominant triterpenoids in Poria cocos (Hoelen) has the sedative-hypnotic effects, and underlying mechanisms are mediated via gamma-aminobutyric acid (GABA)-ergic systems. Oral administration of PA markedly suppressed locomotion activity in mice. This compound also prolonged sleeping time, and reduced sleep latency showing synergic effects with muscimol (0.2 mg/kg) in shortening sleep onset and enhancing sleep time induced by pentobarbital, both at the hypnotic (40 mg/kg) and sub-hypnotic (28 mg/kg) doses. Additionally, PA elevated intracellular chloride levels in hypothalamic primary cultured neuronal cells of rats. Moreover, Western blotting quantitative results showed that PA increased the amount of protein level expression of GAD65/67 over a broader range of doses. PA increased alpha- and beta-subunits protein levels, but decreased gamma-subunit protein levels in GABA(A) receptors. The present experiment provides evidence for the hypnotic effects as PA enhanced pentobarbital-induced sleeping behaviors via GABA(A)-ergic mechanisms in rodents. Taken together, it is proposed that PA may be useful for the treatment of sleep disturbed subjects with insomnia.