5-HT_1A receptor activation potentiates the spinal motor behaviour produced by intrathecal injection of a 5-HT₂ agonist in rats

Intrathecal administration of 5-hydroxytryptamine (5-HT) agonists produces a behavioural syndrome which includes lateral head weaving, reciprocal forepaw treading, wet-dog shakes (WDS) and back muscle contractions (BMC). While 5-HT 2 receptor activation evokes WDS and BMC (Fone et al., 1989), 5-HT_1A receptors appear to be involved in reciprocal forepaw treadipg and lateral head weaving (Tricklebank et al., 1985). Recent evidence indicates that the behaviours evoked by systemic administration of the 5-HT_1A agonist 8-hydroxy-2-(di-n-propylamino)tetraline (8-OHDPAT) are facilitated by co-administration of the selective 5-HT₂ receptor agonist l-(2,5-dimethoxy-4- iodophenyl)-2-aminopropane (DOI) (Arnt and Hyttel 1989). In the present study we determined whether behavioural interaction between these two 5-HT receptor subtypes occurs within the spinal cord.