Original articleSelective agonism of mGlu8 receptors by (S)-3,4-dicarboxyphenylglycine does not affect sleep stages in the rat

BackgroundMetabotropic glutamate receptors (mGlu) play a role in a number of physiological processes and behaviors, as well as in certain pathological conditions and diseases. New drugs targetting mGlu receptors are being developed with treatment purposes. Recent data indicates that glutamate is involved in sleep, and pharmacological manipulation of distinct subtypes of mGlu receptors affect sleep. Here the consequences of selective pharmacological agonism of mGlu8 receptor upon sleep and wakefulness are explored for the first time.Methods32 male Wistar rats were stereotaxically prepared for polysomnography. (S)-3,4-dicarboxyphenylglycine (S)-3,4-DCPG (5, 10, and 20 mg/kg, ip), a selective and potent mGlu8 receptor agonist, or physiological saline was administered one hour after the light period began.ResultsCompared to control vehicle, (S)-3,4-DCPG, did not affect, at any of the doses given, the sleep and wakefulness parameters examined in the general analysis of the three hours of recording. Drug effects across time were studied analyzing three one-hour time blocks, control and experimental groups did not show any significant difference in the sleep and wakefulness parameters analyzed. Latency to sleep stages did not significantly vary between vehicle and treatment groups.ConclusionsResults indicate that pharmacological activation of mGlu8 receptor by (S)-3,4-DCPG (5, 10, 20 mg/kg, ip) does not affect sleep and wakefulness in the rat, suggesting that pharmacological agonism of these receptors may not influence sleep. Further research is needed to verify whether new drugs acting on these receptors lack of effect upon sleep and wakefulness.