ABSTRACT
It is generally accepted that two major subtypes of the serotonin (5–HT) receptor exist in the central nervous system. The differentiation of 5–HT receptors into 5–HT1 and 5–HT2 subtypes was based on the radioligand binding studies of Peroutka & Snyder (1979). Although the 5–HT2 receptor has been characterised only relatively recently (Leysen et al., 1981), progress on the 5–HT1 receptor has been more rapid. At least three subdivisions of this receptor, 5–HT1A, 5–HT1B and 5–HT1C, have been proposed on the basis of binding studies (Pedigo et al., 1981; Schnellmann et al., 1984; Pazos & Palacios, 1985; Pazos et al., 1985a,b) and autoradiographic investigations (Deshmukh et al., 1983; Marcinkiewicz et al., 1984). In terms of receptor function, there are few, if any, well defined tests for 5–HT1 receptors, in contrast to 5–HT2 receptors for which in vivo tests have been reported (Arnt et al., 1984).
