Central administration of p-octopamine to mice: assessment of antinociception

Administration of p-octopamine by intracerebroventricular (i.c.v.) or intrathecal (i.t.) routes, but not orally, produced antinociception in the acetylcholine-induced abdominal constriction test (ED 50 = 24.8 and 3.6 μg, respectively). Likewise, i.c.v. and i.t., but not peripheral (up to 200 mg/kg s.c.), administration increased latency in the 48°C hot-plate test (ED 50 = 11.5 μg i.c.v. and 0.2 μg i.t.). These actions were relatively long-lasting and not blocked by naloxone. Antinociception following i.c.v. administration was abolished in reserpinized mice or by pretreatment with i.t. phentolamine (2 μg). These results suggest a moderate antinociceptive action of p-octopamine involving non-opioid. reserpine-sensitive, central pathways.