5-Hydroxytryptamine(2A) and 5-hydroxytryptamine(1B) 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 transgeni c Tg8 mice where deletion of the gene encoding monoamine oxidase-A results in serotonin (5-hydroxytryptamine (HT)) excess, whole cell recordings of id entified phrenic motoneurons (Phr Mns) were performed to study the modulati on 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 o f the 5-HT1B one suggest that the two types of receptors respond differentl y to 5-HT level changes. (C) 2000 Elsevier Science Ireland Ltd. Ail rig hts reserved.