Grant Number: 5R01MH051234-10
Project Title: Development of Prefrontal Inhibition and Schizophrenia
PI Information: PROFESSOR DAVID A. LEWIS, lewisda@upmc.edu 

Abstract: DESCRIPTION (provided by applicant):
A subset of GABA neurons in the dorsolateral prefrontal cortex (DLPFC) is altered in subjects with schizophrenia. The affected neurons include parvalbumin (PV)-containing chandelier neurons whose axon terminals form vertical arrangements ("cartridges") that synapse exclusively on the axon initial segment (AIS) of pyramidal cells. Networks of PV-containing GABA neurons give rise to gamma band oscillations, and impairments in working memory function in schizophrenia are accompanied by reductions in DLPFC gamma band power. Thus, alterations in PV-containing chandelier neurons may play a critical role in the pathophysiology of working memory dysfunction in schizophrenia. Understanding this role requires knowledge of the normal development of chandelier neurons during adolescence, the typical age of onset of schizophrenia. In the monkey DLPFC, the densities of chandelier axon cartridges immunoreactive (IR) for PV or the GABA membrane transporter (GAT1) markedly decline during adolescence. Because reductions in PV and GAT1 increase the release and efficacy of GABA in response to repetitive stimuli, a decline during adolescence in PV and GAT1 in cartridges may substantially enhance the chandelier neuron regulation of pyramidal cell output, and contribute to the maturation of working memory performance. Thus, the proposed studies are designed to determine whether the normal maturation of monkey DLPFC chandelier neurons during adolescence strengthens their ability to regulate pyramidal cell output and to synchronize the activity of larger groups of pyramidal cells at gamma frequencies. Aims 1-3 tests the hypothesis that adolescence is associated with decreased PV and GAT1 proteins in cartridges, and Aim 4 tests the hypothesis that these changes are associated with an increased efficacy of chandelier neuron inputs to pyramidal cells under the repetitive firing present during working memory tasks. Aim 5 examines changes in chandelier cells during adolescence that may increase their ability to generate gamma oscillations, and Aim 6 tests the hypothesis that gamma band power in the DLPFC increases during adolescence. The strengths of the proposed studies include the integration of anatomical, molecular and electrophysiological techniques in a primate model system to explore the cellular and circuitry bases for the normal maturation of working memory performance and to inform the pathophysiology of working memory dysfunction in schizophrenia.

Thesaurus Terms:
age difference, developmental neurobiology, gamma aminobutyrate, intercellular connection, neuroregulation, prefrontal lobe /cortex, schizophrenia, short term memory
ankyrin, biological model, calcium flux, developmental psychology, electrophysiology, membrane transport protein, neural transmission, neuropathology, pyramidal cell
Macaca mulatta, animal puberty, behavioral /social science research tag, in situ hybridization, juvenile animal

Institution: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
350 THACKERAY HALL
PITTSBURGH, PA 15260
Fiscal Year: 2006
Department: PSYCHIATRY
Project Start: 30-SEP-1995
Project End: 31-JAN-2010
ICD: NATIONAL INSTITUTE OF MENTAL HEALTH
IRG: NPAS 

The Journal of Neuroscience, March 21, 2007, 27(12):3295-3304

Amygdala Gene Expression Correlates of Social Behavior in Monkeys Experiencing Maternal Separation

Michael J. Sabatini,^1,3 Philip Ebert,^7,8 David A. Lewis,^1,2 Pat Levitt,^1,7,8 Judy L. Cameron,^1,4,5 and Károly Mirnics^1,6,8

Departments of ¹Psychiatry, ²Neuroscience, and ³Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, ⁴Departments of Physiology and Pharmacology and Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239-3098, ⁵Oregon National Primate Research Center, Beaverton, Oregon 97006-3448, and Departments of ⁶Psychiatry and ⁷Pharmacology and ⁸Vanderbilt Kennedy Center for Human Development, Vanderbilt University, Nashville, Tennessee 37203

Maternal separation paradigm
A total of 12 female rhesus monkeys born in the breeding colony at the University of Pittsburgh Primate Research Laboratory were used for these studies. At birth, each monkey was arbitrarily selected to enter the "1 week separated," "1 month separated," or "control" experimental groups (n = 4 per group). All monkeys in this study spent the first week of life in a single cage with their mother. During this initial period, monkeys were housed in cages in temperature-controlled (24 ± 2°C) communal rooms with artificial lighting from 7:00 A.M. to 7:00 P.M., Purina Monkey Chow was provided once daily (number 5045; Ralston Purina, St. Louis, MO), and water was available ad libitum. After the first week of life, the animals were handled differently depending on experimental group assignment. At 1 week of age, monkeys designated as 1 week separated were removed from their mothers and placed in a single cage immediately adjacent to a group-rearing pen that they would ultimately join. After a 5–7 d period of learning to bottle feed (ad libitum Similac with Iron baby formula; Abbott Laboratories, Columbus OH), these monkeys were introduced into the group-rearing environment. One week separated monkeys spent weeks 3–12 in the group-rearing environment. Conversely, at 1 week of age, monkeys designated as 1 month separated were introduced into a group-rearing pen with their mothers. One month separated monkeys spent weeks 2–4 in the group-rearing environment with their mothers. At 4 weeks of age, 1 month separated monkeys' mothers were removed from the group-rearing environment, and the infants were placed in the single cage positioned identically as described for the 1 week separated group. After a 5–7 d period of learning to bottle-feed, these monkeys were reintroduced into the group-rearing environment. One month separated infants again spent weeks 6–12 in the group-rearing environment. Monkeys from both separation groups were provided a soft-cotton stuffed toy when they were in the single cage learning to bottle feed. This toy could be held to provide contact comfort. Control monkeys were introduced into the group-rearing pen at 1 week of age with their mother, and they remained there with their mother for the study's entirety, weeks 2–12. The group-rearing pen consisted of 4–5 monkeys of varying ages, with no monkey more dominant than the adult female mother (when present). An adolescent female was always present in the social rearing groups because they have been shown to be particularly attentive to infants. The group-rearing pen, measuring 14 x 11 x 12 feet, was cement block construction with a several inch bed of wood shavings on the floor, four perches at various heights, and a chain-link penfront. A "nursery chamber", measuring 2 x 2 x 3 feet, was placed in each pen and accessible only to infants. Infants had access to bottles of standard human artificial formula that were replaced three times each day. Other monkeys were fed one meal per day between 9:00 and 10:00 A.M. of Purina high-protein monkey chow supplemented several times a week with fresh fruit and seeds strewn in the bedding to encourage foraging. Water was available ad libitum. Artificial lighting in the hallways was on from 7:00 A.M. to 7:00 P.M. each day, and sky lights above each pen admitted natural light. Temperature was maintained at 24 ± 2°C. The infant monkeys were weighed weekly, and all animals, regardless of maternal separation status, reported a comparable weight gain over time (supplemental material 1, available at www.jneurosci.org ).

Behavioral assays
Behavioral assessments were initially made at the time of separation and again during the third month of life and will be described briefly below.
Acute separation behaviors. At the time of maternal separation, each monkey (four 1 week separated and four 1 month separated) was videotaped in the single nursery cage setting for 10 min per focal session. This occurred two to four times per day for the first 3 d after maternal separation, and every other day thereafter, until the infant was transferred to the group-rearing pen. All behaviors displayed by the focal monkeys in the acute separation cage (Table 1)
Table 1. Acute separation behaviors