To better understand the central mechanisms that mediate increases in heart rate (HR) during psychological stress, we examined the effects of systemic and intramedullary (raphe region) administration of the serotonin-1A (5-HT(1A)) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT) on cardiac changes elicited by restraint in hooded Wistar rats with preimplanted ECG telemetric t...