Astrocytes Implicated In Machinery Of Cannabinoid Signaling

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Astrocytes Implicated In Machinery Of Cannabinoid Signaling

http://www.medicalnewstoday.com/articles/101891.php

The brain cells called astrocytes, and not just neurons, are

sensitive to the substances called cannabinoids - the active

chemicals in marijuana.

The researchers said their findings could aid in development of

treatments for cannabinoid drug abuse. Also, because so-

called " endocannabinoids " produced by brain cells are involved in the

neural machinery of pain perception and learning and memory, the

findings could help in understanding those processes, said the

researchers. Marta Navarrete and Alfonso Araque published their

findings in the March 27, 2008, issue of the journal Neuron,

published by Cell Press.

Astrocytes do not transmit nerve impulses, as do neurons. Rather,

they provide neurons with support and nutrition and modulate

signaling among neurons.

In their experiments with mouse brain slices, Navarrete and Araque

sought to establish the role that cannabinoid receptors on

astrocytes - which previous studies had indicated to exist - played

in astrocyte function. Receptors are proteins that rest in the

membranes of cells and that are triggered by specific chemicals, like

a key fitting a lock. That triggering activates a cellular response.

The researchers' electrophysiological and imaging studies showed that

astrocytes do express endocannabinoid receptors that, when activated,

produce a cellular response. They also found that neurons associated

with the astrocytes release endocannabinoids that trigger an

astrocyte response. Finally, they also showed that this response in

astrocytes can, in turn, activate neurons to release the

neurotransmitter glutamate, which mediates signaling among neurons.

Navarrete and Araque concluded that " These results indicate that

neurons and astrocytes communicate via endocannabinoid signaling and

suggest the existence of intercellular communication pathways

mediated by endocannabinoid-glutamate signaling where astrocytes

serve as a bridge for interneuronal communication. "

The researchers also concluded that their findings identify

astrocytes " as cellular elements possibly involved in the physiology

of cannabinoid addiction as well as potential targets for the

treatment of cannabinoid-related drug abuse. Furthermore, considering

the importance of the endocannabinoid-mediated intercellular

signaling in numerous processes of the nervous system, such as pain

perception or learning and memory, present findings indicate that

astrocytes may be actively involved in relevant phenomena of brain

physiology.