ELECTROMYOGRAPHIC EFFECTS OF SEROTONIN APPLICATION INTO THE LATERAL VESTIBULAR NUCLEUS

ELECTROMYOGRAPHIC responses (EMGs) of limb muscles were studied during microiontophoretic application of 5-hydroxytryptamine (5-HT) into the lateral vestibular nucleus (LVN) or the spinal vestibular nucleus (Sp Ve) of anaesthetized rats. The aim was to ascertain whether the level of 5-HT in these nuclei was able to modulate muscle responsiveness. In creased levels of 5-HT in LVN land to a weaker extent in SpVe) enhance d the EMGs of proximal extensor muscles and depressed those of flexors . The 5-HT,, receptor antagonist ketanserin, applied into the LVN, pre vented 5-HT effects on EMG-evoked responses. It is concluded that 5-HT can modulate the motor output via the vestibulospinal pathway, exerti ng a differential control over flexor and extensor muscles. NeuroRepor t 9: 2539-2544 (C) 1998 Rapid Science Ltd.