“…It is currently thought that the a 1 -receptors involved in motor activity exert this function in large part via modulatory effects on dopaminergic neuronal firing rate (Berretta et al, 2000;Grenhoff et al, 1993Grenhoff et al, , 1995, presynaptic release of DA (Gioanni et al, 1998;Mathé et al, 1996;Auclair et al, 2002), and/or potentiation of postsynaptic dopaminergic signaling (Eshel et al, 1990). However, DA-independent effects may also be involved since many a 1 -receptors are located on motorneurons downstream of dopaminergic neurons (Hou et al, 2002) and also on or near serotonergic and noradrenergic neurons (Morin et al, 1996).…”