Alteration of neocortical activity in response to noxious stimulation: participation of the dorsal raphe.
Noxious stimulation induces cortical desynchronization which in turn can suppress epileptic seizures in humans and epileptiform activity in laboratory animals. Recent evidence indicates that serotonin mediates both atropine-resistant cortical desynchronization and the suppression of focal epileptiform activity induced by noxious stimulation. As a large forebrain projection of serotonergic fibres originates from the dorsal raphe nucleus, involvement of this nucleus in altering cortical activity was investigated. Agents known to inhibit serotonergic unit activity including serotonin, (+/-)-8-hydroxy-dipropylaminotetralin, fluoxetine and baclofen, when pressure ejected in the vicinity of the dorsal raphe, prevented cortical desynchronization as well as the suppression of focal epileptiform activity in response to noxious stimulation. From these observations it is concluded that serotonergic neurones of the dorsal raphe can profoundly influence neocortical excitability and this action may underlie the clinical effectiveness of strong or noxious stimuli in suppressing epileptic seizures.
Thompson
P M
PM
Faculty of Medicine, Memorial University, St John's, Newfoundland, Canada.
Zebrowski
G
G
Neuman
R S
RS
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002540:Cerebral Cortex / Q000502:physiology*; D003344:Cortical Synchronization; D004827:Epilepsy / Q000503:physiopathology; D005473:Fluoxetine / Q000494:pharmacology; D008297:Male; D010812:Physical Stimulation; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology; D013764:Tetrahydronaphthalenes / Q000494:pharmacology
D012702:Serotonin Antagonists; D013764:Tetrahydronaphthalenes; D005473:Fluoxetine; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D001418:Baclofen