Study may help explain 'awakenings' that occur with popular sleep-aid Ambien

Jun 29, 2009

Some people who take the fast-acting sleep-aid zolpidem (Ambien) have been observed walking, eating, talking on the phone and even driving while not fully awake. Many often don't remember doing any of these activities the next morning. Similarly, this drug has been shown to awaken the minimally conscious into a conscious state. A new study by Georgetown University Medical Center (GUMC) researchers may help explain why these "awakenings" occur.

The study, published online in the Monday, suggests that while some powerful are shut down with zolpidem, the powerful activates other circuits when deprived of activity.

" or neurons are highly reactive to incoming activity throughout life," explains Molly M. Huntsman, an assistant professor in the department of pharmacology at Georgetown University Medical Center and corresponding author for the study. "When is silenced, many neurons automatically react to this change. We see this in our study which suggests that inhibitory neurons responsible for stopping neural activity are themselves shut down by zolpidem. The excitatory neurons, responsible for transmitting activity, are then allowed to re-awaken and become active again, without monitoring because the inhibitory neurons are 'asleep'."

Rodents are especially dependent upon their whiskers to explore their environment; for the study, researchers trimmed the whiskers of mice (while under anesthesia). They then studied the region of the brain responsive to whisker movements to examine activity-dependent brain circuits. After removing the whiskers and depriving neural activity, the inhibitory neurons that normally don't respond to sedation by zolpidem underwent a change, becoming more sensitive. The researchers posited that these neurons are shut down and, in turn, not able to monitor other brain circuits.

"This was really unexpected. It appears the receptors on some inhibitory neurons were changed and were able to be inhibited by zolpidem, preventing them from performing their normal functions. We merely wanted to use zolpidem as a tool to examine which type of functional inhibitory receptor is expressed in certain neurons. Yet it turns out that sensory deprivation in the form of whisker trimming is enough to alter the receptor composition expressed in these cells." Huntsman says.

Researchers say that while the study suggests that zolpidem shuts down active neural pathways and perhaps then triggers others, the activation of this trigger is unknown.

"Nevertheless, the paradoxical activation of brain circuits by a powerful sedative definitely needs more attention in additional studies both human and in animal models," Huntsman concludes.

Source: Georgetown University Medical Center (news : web)

Explore further: First vital step in fertilization between sperm and egg discovered

add to favorites email to friend print save as pdf

Related Stories

Insomnia drug can improve brain function

Mar 13, 2007

A new study reported that zolpidem, a drug normally used to treat insomnia, temporarily improved brain function in a patient suffering from akinetic mutism, a condition in which the person is alert but cannot speak or move. ...

Research shows how sensory-deprived brain compensates

Apr 17, 2007

Whiskers provide a mouse with essential information to negotiate a burrow or detect movement that could signal a predator's presence. These stiff hairs relay sensory input to the brain, which shapes neuronal activity. In ...

Stem cells are good for the brain

Jul 15, 2008

For some years, scientists have been speculating over why stem cells exist in the brain, as brain regeneration is limited. A German team of neuroscientists believe these stem cells help keep the brain healthy and active.

Pulsing light silences overactive neurons

Mar 27, 2007

Scientists at the MIT Media Lab have invented a way to reversibly silence brain cells using pulses of yellow light, offering the prospect of controlling the haywire neuron activity that occurs in diseases such ...

Recommended for you

Researchers transplant regenerated oesophagus

Apr 15, 2014

Tissue engineering has been used to construct natural oesophagi, which in combination with bone marrow stem cells have been safely and effectively transplanted in rats. The study, published in Nature Communications, shows ...

User comments : 0

More news stories

HIV+ women respond well to HPV vaccine

HIV-positive women respond well to a vaccine against the human papillomavirus (HPV), even when their immune system is struggling, according to newly published results of an international clinical trial. The study's findings ...

Progress in the fight against quantum dissipation

(Phys.org) —Scientists at Yale have confirmed a 50-year-old, previously untested theoretical prediction in physics and improved the energy storage time of a quantum switch by several orders of magnitude. ...

Revealing camouflaged bacteria

A research team at the Biozentrum of the University of Basel has discovered an protein family that plays a central role in the fight against the bacterial pathogen Salmonella within the cells. The so cal ...