Dendritic Remodeling in the Adolescent Medial Prefrontal Cortex and the Basolateral Amygdala of Male and Female Rats WENDY A. KOSS, 1 CHELSEA E. BELDEN, 1 ALEXANDER D. HRISTOV, 1 AND JANICE M. JURASKA 1,2 * 1 Department of Psychology, University of Illinois Urbana-Champaign, Champaign, Illinois 61820 2 Program in Neuroscience, University of Illinois Urbana-Champaign, Champaign, Illinois 61820 KEY WORDS puberty; dendritic spines; Golgi, synapse; dendrite; sex differences; adolescence ABSTRACT There is recent evidence of continuing development throughout ado- lescence in two neural areas involved in emotion and cognition, the basolateral amyg- dala (BLN) and the medial prefrontal cortex (mPFC). Previous research from our laboratory has demonstrated a cellular loss in both of these brain regions in rats between postnatal day (P) 35 and 90. This study investigates dendritic changes in pyramidal neurons of the BLN and Layer 5 of the mPFC at P20 (juvenile), 35 (puberty), and 90 (adulthood) in hooded rats of both sexes. Dendritic branching and dendritic spines were quantified in Golgi-Cox impregnated tissue. Between P20 and 35, dendritic length and complexity, as well as the density of dendritic spines, increased in both structures. Between P35 and 90, dendritic spines in the mPFC neu- rons significantly decreased in both sexes, while a loss of basilar dendrites was only detected in females. In the BLN, there was an increase in the number of branches between P35 and 90 without an increase in the total length of the dendritic tree. BLN spine density also remained stable during this period. These results show that the den- dritic tree grows prior to puberty while dendritic remodeling and pruning occurs after puberty in both of these neural areas. This late development may lead to susceptibil- ities to psychopathologies and addictions that often develop at this time. Synapse 68:61–72, 2014. V C 2013 Wiley Periodicals, Inc. INTRODUCTION Adolescence is noted for emotional turmoil, increased vulnerability to addiction and the onset of psychiatric disorders, such as depression and schizo- phrenia, often with sex differences in onset and prev- alence (Kessler et al., 2001; Spear, 2000; Weinberger, 1994). The prefrontal cortex (PFC) and the amygdala are interconnected and are both involved in these dis- orders which suggests functional changes in these neural regions during adolescence (Benes and Gisa- bella, 2006; Drevets, 1999; Ernst et al., 2009). In addition, the behavioral abilities of adolescents on many tasks associated with these areas are immature when compared to adults. In human adolescents, working memory, attention, processing speeds and reactions to emotional stimuli are not yet at adult levels (Anderson et al., 2001; Graber et al., 1996; Kill- gore et al., 2001; Levin et al., 1991; Monk et al., 2003). Similarly, rats show improvement from adoles- cence to adulthood in several types of tasks including working and spatial memory, fear conditioning and tests of anxiety (Koss et al., 2011; Niemi and Thomp- son, 1980; Rubinow, 2009b; Schenk, 1985; Wieden- mayer, 2009). These studies imply that the mPFC and the amygdala are not fully developed function- ally until adulthood. Structural MRI studies of humans have reported changes in both of these neural regions throughout the adolescent period. In the PFC, gray matter vol- ume increases throughout childhood with a peak around 11–12 years old, followed by a decrease Contract grant sponsor: National Institutes of Health, NIAAA; Contract grant number: AA017354; Contract grant sponsor: NIMH; Contract grant number: MH099625. *Correspondence to: Janice M. Juraska, Department of Psychology, Univer- sity of Illinois Urbana-Champaign, 603 E. Daniel Street, Champaign, IL 61820. E-mail: jjuraska@illinois.edu Received 10 June 2013; Accepted 31 August 2013 DOI: 10.1002/syn.21716 Published online 19 September 2013 in Wiley Online Library (wileyonlinelibrary.com). Ó 2013 WILEY PERIODICALS, INC. SYNAPSE 68:61–72 (2014)