title: Involvement of the periaqueductal gray in the effect of motor cortex stimulation.
abstract: Several clinical and animal studies of different pain models reported that motor cortex stimulation (MCS) has an antinociceptive effect. In our previous study, the response of the primary somatosensory cortex (SI) to peripheral stimuli decreased after MCS. The aim of the present study was to investigate involvement of the periaqueductal gray (PAG) in this inhibitory effect of MCS. Responses of the SI to electrical stimuli applied to both forepaws of anesthetized rats were monitored to evaluate the effect of MCS. After sensory-evoked potentials (SEPs) were stable, either saline, opioid, or dopamine receptor antagonists were locally microinjected into the PAG. After drug or saline administration, MCS was applied to the forepaw area of the right motor cortex. SEPs after MCS were compared to those before MCS. In the saline group, SEPs ipsilateral to MCS decreased, but SEPs contralateral to MCS did not. The decrease in SEPs was prevented by pretreatment of the PAG with naloxone. Application of a nonspecific dopamine receptor antagonist (α-flupenthixol) to the PAG also blocked the inhibition of SEPs after MCS. Inhibition of SEPs after MCS was blocked by local application of a D1 antagonist (SCH-23390) in the PAG, but not by a D2 antagonist (eticlopride). These results suggest that the PAG participates in the inhibitory effect of MCS, and this effect of MCS may be mediated by opioid and dopamine D1 receptors within thePAG.
authors: Department of Anatomy, School of Medicine, College of Medicine, Taipei Medical University, 250 Wu-Hsing Street, Taipei City 10031, Taiwan, ROC.
authors: Ruei-Jen
authors: RJ
authors: Chiou
authors: Chen-Wei
authors: CW
authors: Chang
authors: Chung-Chih
authors: CC
authors: Kuo
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D005475:Flupenthixol / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D009044:Motor Cortex / Q000187:drug effects / Q000502:physiology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012457:Salicylamides / Q000494:pharmacology; D013003:Somatosensory Cortex / Q000187:drug effects / Q000502:physiology
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D009292:Narcotic Antagonists; C534628:SCH 23390; D012457:Salicylamides; D009270:Naloxone; D005475:Flupenthixol; C045989:eticlopride