GABAB-RI receptors in serotonergic neurons: effects of baclofen on 5-HT output in rat brain.
The activation of GABAB receptors hyperpolarizes 5-HT neurons and reduces cell firing. In situ hybridization showed the presence of the GABAB-RI receptor transcript in virtually all 5-HT neurons of the dorsal and median raphe nuclei (DR and MnR, respectively) whereas the GAD transcript was present mainly outside these nuclei. The systemic administration of baclofen increased the in vivo 5-HT release in the DR, MnR and several projection areas. As shown previously in the DR, the application of baclofen in the MnR increased the local 5-HT output. Thus, although 5-HT neurons contain inhibitory GABAB-RI receptors, baclofen increased 5-HT release in some brain areas, likely by a preferential action on terminal GABAB autoreceptors in inhibitory inputs to 5-HT neurons. The scarcity of GAD-expressing cells in the DR and MnR suggests that these inputs originate mainly outside these nuclei.
Abellán
M T
MT
Department of Neurochemistry, Instituto de Investigaciones Biomédicas de Barcelona, CSIC (IDIBAPS).
Adell
A
A
Honrubia
M A
MA
Mengod
G
G
Artigas
F
F
D000818:Animals; D001418:Baclofen / Q000494:pharmacology*; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D018755:GABA Agonists / Q000494:pharmacology*; D005968:Glutamate Decarboxylase / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D026901:Membrane Transport Proteins; D017551:Microdialysis; D009419:Nerve Tissue Proteins; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011903:Raphe Nuclei / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000187:drug effects* / Q000235:genetics*; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D002352:Carrier Proteins; D018755:GABA Agonists; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D018080:Receptors, GABA-B; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; D001418:Baclofen