NEUROPHARMACOLOGY AND NEUROTOXICOLOGYB-RI">GABAB-RI receptors in serotonergic neurons Effects of baclofen on 5-HT output in rat brainAbellán, María T.1; Adell, Albert1; Honrubia, M Angeles1; Mengod, Guadalupe1; Artigas, Francesc1,2Author Information 1Department of Neurochemistry, Instituto de Investigaciones Biomédicas de Barcelona, CSIC (IDIBAPS), Rossello 161, 08036, Barcelona 2Corresponding Author: Francesc Artigas Acknowledgements: Work supported by grants FIS 98-0697 and SAF 99-0123. M.T.A. is recipient of a fellowship from the Institut d'Investigacions Biomédiques August Pi i Sunyer (IDIBAPS). We thank Leticia Campa for her skilful technical assistance. Thanks are given to Lundbeck A/S for their kind supply of citalopram. Received 22 December 1999; accepted 20 January 2000 NeuroReport: April 7, 2000 - Volume 11 - Issue 5 - p 941-945 Buy Abstract The activation of GABAB receptors hyperpolarizes 5-HT neurons and reduces cell firing. In situ hybridization showed the presence of the B-RI">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 B-RI">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. © 2000 Lippincott Williams & Wilkins, Inc.