Neonatal 6-hydroxydopa alters conspecific odor investigation by male rats

Odor-guided behavior was examined in male rats injected at birth and 48 h later with either the catecholaminergic neurotoxin 6-hydroxydopamine (60 micrograms/g, i.p.) or vehicle. In odor preference tests administered 8 or 74 days postnatally, drug-treated animals avoided novel odors which were neutral for controls and showed reduced preference for conspecific nest odors. In emergence tests administered 73-75 days postnatally, odors from an anesthetized female reduced approach latency and increased investigation of familiar conspecific odors for control but not drug-treated males. Neonatal drug treatment decreased adult olfactory cortex norepinephrine (NE) levels by 50%, but did not significantly influence either cardiac NE or olfactory cortex dopamine. The results imply that brain NE facilitates attraction to familiar conspecific odors.