Electrophysiological evidence for postsynaptic 5-HT(1A) receptor control of dorsal raphe 5-HT neurones.
Postsynaptic 5-hydroxytryptamine(1A) (5-HT(1A)) receptors have been proposed to participate in the control of dorsal raphe 5-HT neurone activity. To further investigate this hypothesis we performed single-unit extracellular recordings in anaesthetized rats. Pertussis toxin (2 microg/4 microl/day; 2 days, 24-72 h before the experiment) was applied close to the dorsal raphe nucleus to uncouple somatodendritic 5-HT(1A) autoreceptors from their effector system. After this treatment the spontaneous firing rate was higher (approximately +60% P<0.005) than in the vehicle-pretreated group. In addition, intravenous administration of 8-hydroxy-2-(di-n-propylamino)tetralin HBr (8-OH-DPAT) inhibited 5 out of 11 cells of the pertussis toxin-pretreated group (ED(50)=1.65+/-0.94 microg/kg), whereas in the vehicle-pretreated group, all tested cells were inhibited (ED(50)=1.87+/-0.39 microg/kg). Local administration of 8-OH-DPAT did not affect cells (n=12) in pertussis toxin-pretreated rats, even at doses much higher than those needed to completely inhibit 5-HT cells in vehicle-pretreated rats (ED(50)=3.34+/-0.62 fmol). These results confirm the involvement of distal postsynaptic 5-HT(1A) receptors in the control of 5-HT neurone activity in the dorsal raphe nucleus. However, this control does not appear to be exerted on all 5-HT neurones, but rather on a subpopulation of them.
Martín-Ruiz
R
R
Department of Pharmacology, Faculty of Medicine, University of the Basque Country, 48940 Leioa, Vizcaya, Spain.
Ugedo
L
L
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D017660:Autoreceptors / Q000187:drug effects; D004594:Electrophysiology; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D037342:Pertussis Toxin; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D015290:Second Messenger Systems; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D017660:Autoreceptors; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D010566:Virulence Factors, Bordetella; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D037342:Pertussis Toxin