The adolescent brain and age-related behavioral manifestations

Abstract

To successfully negotiate the developmental transition between youth and adulthood, adolescents must maneuver this often stressful period while acquiring skills necessary for independence. Certain behavioral features, including age-related increases in social behavior and risk-taking/novelty-seeking, are common among adolescents of diverse mammalian species and may aid in this process. Reduced positive incentive values from stimuli may lead adolescents to pursue new appetitive reinforcers through drug use and other risk-taking behaviors, with their relative insensitivity to drugs supporting comparatively greater per occasion use. Pubertal increases in gonadal hormones are a hallmark of adolescence, although there is little evidence for a simple association of these hormones with behavioral change during adolescence. Prominent developmental transformations are seen in prefrontal cortex and limbic brain regions of adolescents across a variety of species, alterations that include an apparent shift in the balance between mesocortical and mesolimbic dopamine systems. Developmental changes in these stressor-sensitive regions, which are critical for attributing incentive salience to drugs and other stimuli, likely contribute to the unique characteristics of adolescence. ᭧

Adolescent Rats Find Repeated Δ9-THC Less Aversive Than Adult Rats but Display Greater Residual Cognitive Deficits and Changes in Hippocampal Protein Expression Following Exposure

“…Adolescent behavior in rodents is characterized by greater social interaction and exploratory behavior relative to adults (Spear, 2000) and such effects were evident in control rats in the social interaction and EPM tasks in the present study. Hence, it is most likely that the higher open-arm time at baseline in the adolescent rats allowed a greater margin for reduction by acute D 9 -THC treatment.…”

“…Of these, 24 were 28 days old (adolescent) and 24 were 60 days old (adult) on delivery to our colony, consistent with the adolescent ontogenetic window of 28-55 days for rats (Spear, 2000). For each developmental cohort, 12 rats were chronically exposed to D 9 -THC with the other 12 serving as vehicle (VEH)-treated controls.…”

Adolescent Cannabis Exposure Alters Opiate Intake and Opioid Limbic Neuronal Populations in Adult Rats

“…i.p.) or vehicle (0.9% NaCl with 0.3% Tween 80) during PNDs 28-49 to extend beyond the prototypic adolescent period (days 28-42), which starts around 10 days before puberty and ends a few days after (Spear, 2000), into mid-adolescence (Andersen, 2003). In order to mimic the intermittent use seen in teenagers, the drug was given once every third day; this resulted in a total of eight injections.…”

Does Prenatal Nicotine Exposure Sensitize the Brain to Nicotine-Induced Neurotoxicity in Adolescence?

“…The nicotine exposure period thus spans the recognized boundaries of adolescence in the rat, as typified by endocrine, pubertal, and behavioral parameters (Spear, 2000). In the adolescent rat this paradigm produces plasma nicotine levels of 25 ng/ ml, similar to that in typical smokers (Lichtensteiger et al, 1988;Trauth et al, 2000b); it produces a transient (10%) reduction in body weight during treatment, an effect that disappears after termination of the infusion (Abreu-Villaça et al, 2003a;Trauth et al, 1999).…”