Johanson, Ingrid B.

The effects of cocaine exposure and maternal deprivation on subsequent voluntary ingestion of cocaine and amphetamine was investigated in 7-day-old rat pups in order to further our understanding on the development of drug addiction. Maternally deprived and non-deprived pups were pre-exposed to a cocaine solution masked with 5% orange Tang solution. Four hours later, experimental pups were tested for subsequent cocaine self-administration (SA) (Exp. 1) or amphetamine SA, (Exp. 2), following a second deprivation period. Control pups were not deprived during this interval. Pups in both experiments were assessed for dose self-administered and for general activity. Results indicate that cocaine pre-exposure increased cocaine and amphetamine SA, and activity significantly increased after pre-exposure and testing sessions. Lastly, sensitization of the motor effects of cocaine was observed in pups pre-exposed to cocaine. This study provides a potential drug SA animal model not yet investigated in developing animals.

This study was designed to develop an animal model of Attention Deficit Hyperactivity Disorder based on frontal cortical functioning in 3, 6, 9, & 12-day-old neonatal rats. In Expt. 1, frontal cortical activity was suppressed with intracranial injections of lidocaine, a local anesthetic. In Expt. 2, frontal activity was suppressed with brain transections. Pups in both experiments were tested in a habituation-to-odor learning paradigm and behaviors including general activity, headwaving, probing, and rolling were recorded. Results indicated that frontal cortical suppression, caused by either lidocaine injection or brain transection, resulted in significantly higher activity levels in 3-day-olds particularly with regard to rolling, suggesting that the frontal cortex is involved in the regulation of rolling behavior. Frontal transections, but not lidocaine injections, also significantly increased activity in 12-day-old pups due to increased locomotor probing and wall climbing. Results are consistent with the neuropsychological research regarding frontal cortical functioning and inhibition in children with ADHD, and show potential as a future animal model of ADHD.

Prenatal exposure to cocaine has been associated with a variety of deleterious effects on human infants. In this study, several measures were examined using the rat as a model of the clinical effects found in children of cocaine-abusing mothers. Infant rats exposed to 40 mg/kg during gestation via injections to their dam do not differ from nutritional and saline controls on such measures as body weight, age of eye opening, latency to attach to a nipple, and preference for a home odor. However, cocaine exposed pups show significantly suppressed levels of play and are more submissive in a play encounter than control pups. The data are discussed in terms of how deficits in play behavior may put the young at a cognitive and social disadvantage.

The effects of prenatal ethanol exposure, via a liquid diet containing 35% ethanol derived calories, on spatial learning were assessed in the radial arm maze and Morris water maze at 30 and 60 days of age. No significant affects of ethanol exposure were found on either task at either age. The effects of postnatal ethanol exposure, via self administration of a 15% ethanol solution, on spatial learning were assessed in the radial arm maze and Morris water maze. No significant effects of ethanol exposure were found on either task at either 30 or 60 days of age. Subtle differences in performance in the radial arm maze were found at 30 days of age in both the prenatally and postnatally ethanol exposed groups. These differences suggest that the exposure to ethanol postnatally may be interfering with the rate of learning and the ability to learn.