Persistent neurobehavioral and neurochemical anomalies in middle-aged rats after maternal diazinon exposure.

We study the interaction of drugs, hormones and environmental factors with the developing organism, with particular emphasis on the fetal and neonatal nervous system. The role of biochemical factors mediating development of nerve cells and other types of tissue is a major thrust, since they influence the subsequent structural and physiological status of critical organ systems. Ongoing projects comprise five areas: (1) Mechanisms regulating development of synapses - role of endocrine and other trophic factors, intracellular messengers in developing cells, control of target organ differentiation by neural input; (2) Adverse effects of exogenous agents on development, with an emphasis on identification of mechanisms by which behavioral or physiological damage occurs - drugs of abuse (especially nicotine), hormonal imbalances, environmental contaminants (especially pesticides), food additives, intrauterine growth retardation, fetal and neonatal hypoxia; (3) Control of fetal and neonatal cardiovascular and respiratory function by the immature nervous system - normal physiological mechanisms, responses to stress, factors mediating the transition from fetal to neonatal function, reactivity during delivery, Sudden Infant Death Syndrome; (4) Breast cancer cell growth regulation - role of hormone and neurotransmitter receptors converging on common cell signaling mechanisms, and targeting of these receptors for cancer therapeutics.

We study the effect of drugs, hormones and environmental factors on the intracellular and extracellular biochemical signals that govern the development of mammalian neural tissues, with particular emphasis on the biochemistry and molecular biology underlying control of replication, differentiation, synaptogenesis and onset of synaptic function.  Ongoing projects comprise the following areas: (1) the role of endocrine and neurotrophic factors in transmitter and receptor choice by developing neurons; (2) effects of drugs of abuse, hormonal imbalances, environmental contaminants and fetal/neonatal hypoxia, on nervous system development; (3) control of fetal/neonatal cardiovascular and respiratory function by the immature nervous system, with particular emphasis on parturition and Sudden Infant Death Syndrome; (4) molecular mechanisms of brain dysfunction in the elderly (Alzheimer's Disease and Depression); (5) control of gene expression in developing cells by trophic factors that operate through defined second messenger systems and protooncogenes.
Research is directed toward understanding the interaction of drugs, hormones and environmental factors with the developing nervous system. The role of these factors in mediating development of nerve cells is a major effort as they influence the subsequent structural and functional state of nervous system and its targets. The approach is multidisciplinary. Ongoing projects involve three areas:

1. Mechanisms regulating the development of synapses and the role of endocrine and other trophic factors (i.e. neurotransmitters) in this regulation. Long-term structural and functional consequences of altered development are evaluated.
2. Adverse effects of exogenous agents on nervous system development, emphasizing the identification of mechanisms by which behavioral or physiological injury occurs. Under investigation are: Drugs of abuse (especially cocaine and nicotine), hormonal imbalances, environmental contaminants (pesticides, flame retardants, etc.), food additives, stress, intrauterine growth retardation and hypoxia.
3. Molecular mechanisms of human brain dysfunction in the elderly, specifically Alzheimer's disease and depression.

New directions are concentrating on neurotransmitter and hormonal regulation of cell differentiation and gene expression:
1. Neurotransmitter control of cell differentiation in the central nervous system. The role of transient receptor expression and transduction in effecting the switch from replication to differentiation and the molecular (epigenetic) mechanism underlying control of early immediate genes.
2.  Consequence of early life exposures on subsequent development of adult decease.  Altered vulnerabilities resulting from multiple exposure events (i.e. fetal nicotine x neonatal pesticide).
3.  Establishing in vitro models to explore the mechanisms abnormalities.

Dr. Levin is Chief of the Neurobehavioral Research Lab in the Psychiatry Department of Duke University Medical Center. His primary academic appointment is as Professor in the Department of Psychiatry and Behavioral Sciences. He also has secondary appointments in the Department Pharmacology and Cancer Biology, the Department of Psychological and Brain Sciences and the Nicholas School of the Environment at Duke. His primary research effort is to understand basic neural interactions underlying cognitive function and addiction and to apply this knowledge to better understand cognitive dysfunction and addiction disorders and to develop novel therapeutic treatments.

The three main research components of his laboratory are focused on the themes of the basic neurobiology of cognition and addiction, neurobehavioral toxicology and the development of novel therapeutic treatments for cognitive dysfunction and substance abuse. Currently, our principal research focus concerns nicotine. We have documented the basic effects of nicotine on learning memory and attention as well as nicotine self-administration. We are continuing with more mechanistic studies in rat models using selective lesions, local infusions and neurotransmitter interaction studies. We have found that nicotine improves memory performance not only in normal rats, but also in rats with lesions of hippocampal and basal forebrain connections. We are concentrating on alpha7 and alpha4beta2 nicotinic receptor subtypes in the hippocampus, amygdala , thalamus and frontal cortex and how they interact with dopamine D1 and D2 and glutamate NMDA systems with regard to memory and addiction. I am also conducting studies on human cognitive behavior. We have current studies to assess nicotine effects on attention, memory and mental processing speed in schizophrenia, Alzheimer's Disease and Attention Deficit Hyperactivity Disorder. In the area of neurobehavioral toxicology, I have continuing projects to characterize the adverse effects of prenatal and adolescent nicotine exposure. Our primary project in neurobehavioral toxicology focuses on the cognitive deficits caused by the marine toxins. The basic and applied aims of our research complement each other nicely. The findings concerning neural mechanisms underlying cognitive function help direct the behavioral toxicology and therapeutic development studies, while the applied studies provide important functional information concerning the importance of the basic mechanisms under investigation.