Serotonergic influence from nucleus raphe obscurus on neurones in the periaqueductal grey matter in the rat.
In rats anaesthetised with urethane, iontophoretic application of 5-hydroxytryptamine (5-HT, 5-70 nA) produced changes in ongoing activity of 41/44 neurones in the periaqueductal grey matter (PAG). The majority (85%) of responsive cells were inhibited and 15% were excited. The inhibitions were mimicked in 5/7 cells by iontophoresis of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 10-30 nA) whilst excitation was produced in 3/5 cells by iontophoresis of the 5-HT2 agonist alpha-methyl-5-HT (10-30 nA). Selective activation of neuronal perikarya in nucleus raphe obscurus (NRO) by microinjection of 50-100 nl D,L-homocysteic acid (DLH) inhibited ongoing activity of 25/31 neurones tested in the PAG for periods of 30-580 s, mean 183.5 s. The duration of the inhibition was potentiated by between 36 and 300% during iontophoresis of the 5-HT re-uptake blocker paroxetine (1-25 nA, 6/6 cells). The results indicate that there is an extensive inhibitory serotonergic input to the PAG which originates, at least in part, from NRO.
Lovick
T A
TA
Department of Physiology, Medical School, University of Birmingham, UK.
D000818:Animals; D002319:Cardiovascular System / Q000187:drug effects; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D007478:Iontophoresis; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D017374:Paroxetine / Q000494:pharmacology; D010487:Periaqueductal Gray / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013268:Stimulation, Chemical; D013681:Tegmentum Mesencephali / Q000187:drug effects
D010879:Piperazines; D012702:Serotonin Antagonists; D006710:Homocysteine; C007956:homocysteic acid; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; D012701:Serotonin; D017374:Paroxetine