Olfactory investigation was examined in male Sprague-Dawley rats injected with 50 mg/kg of the noradrenergic neurotoxin, DSP4, 10 days before testing. In a two-choice preference test, the odor of pine shavings from the nest of a female and her litter attracted sexually experienced control males, but not drug treated males. Further, odors from anesthetized females increased the mean number of entries made by control males, but not drug-treated males, into a cage containing pups' nest shavings. Combining a novel odor with nest shavings significantly reduced the number of entries made by both groups of males. Drug treatment decreased norepinephrine (NE) levels by 66, 62, and 68% in the olfactory cortex, olfactory bulb, and frontal cortex, respectively. Dopamine concentrations were not significantly affected. NE concentrations in the heart, and serotonin levels in the olfactory bulb, were moderately depleted (by 37 and 40%, respectively). The results support the view that central NE modulates systems regulating attraction to conspecific odors in male rats.
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