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SLEEP AND TEMPERATURE REGULATION

Effects on sleep of microdialysis of adenosine A₁ and A_2a receptor analogs into the lateral preoptic area of rats

¹Research Service (151A3), Veteran Affairs Greater Los Angeles Healthcare System, Sepulveda, California; Departments of ²Psychology and ³Medicine, University of California, Los Angeles, California; and ⁴Department of Zoology, Patna University, Patna, India

Submitted 8 April 2005 ; accepted in final form 9 August 2005

Evidence suggests that adenosine (AD) is an endogenous sleep factor. The hypnogenic action of AD is mediated through its inhibitory A₁ and excitatory A_2A receptors. Although AD is thought to be predominantly active in the wake-active region of the basal forebrain (BF), a hypnogenic action of AD has been demonstrated in several other brain areas, including the preoptic area. We hypothesized that in lateral preoptic area (LPOA), a region with an abundance of sleep-active neurons, AD acting via A₁ receptors would induce waking by inhibition of sleep-active neurons and that AD acting via A_2A receptors would promote sleep by stimulating the sleep-active neurons. To this end, we studied the effects on sleep of an AD transport inhibitor, nitrobenzyl-thio-inosine (NBTI) and A₁ and A_2A receptor agonists/antagonists by microdialyzing them into the LPOA. The results showed that, in the sleep-promoting area of LPOA: 1) A₁ receptor stimulation or inhibition of AD transport by NBTI induced waking and 2) A_2A receptor stimulation induced sleep. We also confirmed that NBTI administration in the wake promoting area of the BF increased sleep. The effects of AD could be mediated either directly or indirectly via interaction with other neurotransmitter systems. These observations support a hypothesis that AD mediated effects on sleep-wake cycles are site and receptor dependent.

sleep-wake cycle; A₁ and A_2a receptor activation; nitrobenzyl-thio-inosine; basal forebrain; site specificity