Prenatal buprenorphine exposure and sexually dimorphic nonreproductive behaviors in rats

This set of experiments examined the effects of prenatal buprenorphine (BUP) exposure on three measures of sexual differentiation in rats. Pregnant female rats were divided into four treatment groups: 0.6 mg/kg BUP, 0.3 mg/kg BUP, a pair-fed control (PFC), and an untreated control (UTC). Drugs were injected starting on gestation day (GD) 6 and continuing through GD 20 with a 48-h interval between drug administrations. Three variables were examined in the offspring: anogenital (AG) distance on postnatal day (PND) 1, spontaneous parental behavior on PNDs 23-28, and saccharin consumption on PNDs 42-55. Whereas prenatal BUP exposure had no effect on AG distance, spontaneous parental behavior was impaired in the 0.6-mg/kg-exposed offspring on two measures: pup-retrieval latencies and pup-directed behaviors. Furthermore, although both control groups and the 0.3-mg/kg-exposed offspring showed the expected sex difference in consumption of a 0.25% saccharin solution, this difference was not displayed by the 0.6-mg/kg-exposed offspring. These findings suggest that exposure to relatively high doses of buprenorphine during development may have long-term effects on behavior.