5-Hydroxytryptamine2A and 5-hydroxytryptamine1B receptors are differently affected by the monoamine oxidase A-deficiency in the Tg8 transgenic mouse

In brainstem-spinal cord preparations of neonatal control C3H and transgenic Tg8 mice where deletion of the gene encoding monoamine oxidase-A results in serotonin (5-hydroxytryptamine (HT)) excess, whole cell recordings of identified phrenic motoneurons (Phr Mns) were performed to study the modulation of their activity by 5-HT. In C3H mice, a dual effect was observed: (i) a facilitation via 5-HT2A receptors and (ii) a decrease of the transmission of the central inspiratory drive via 5-HT1B receptors. In Tg8 mice, the 5-HT2A-mediated facilitation was present but the 5-HT1B-mediated decrease was lacking. Therefore, the conservation of the 5-HT2A response vs. the loss of the 5-HT1B one suggest that the two types of receptors respond differently to 5-HT level changes. (C) 2000 Elsevier Science Ireland Ltd. Ail rig hts reserved.