John A. Harvey - US grants

Pavlovian conditioning of the rabbit's nictitating membrane response, a corneal-VIth nerve reflex, is generally agreed to provide a reliable measure of associative learning and memory. This model system will be used to identify the anatomical pathways and neurochemical systems involved in learning and memory and to examine the behavioral and neurochemical processes through which drugs act to alter learning and memory. Experiments will be carried out under three major aims that will provide converging approaches to origin additional knowledge of these basic processes. Aim 1 will examine those brain regions that have been suggested to play an essential or important role in the acquisition and/or performance of conditioned responses. This will include a thorough examination of recent proposals that the cerebellum is essential for the learning of motor acts by the use of cortical (VIth lobe) and subcortical (interpositus) lesions of the cerebellum and from reversible lesions produced by infusion of lidocaine. The reversible lesion will then be employed to establish whether interpositus is essential for the acquisition of conditioned responses. These reversible lesions will also be used to identify other pathways of the conditioned and unconditioned response. Aim 2 will examine the uptake of 3H- and 14C-2-deoxy-D-glucose in a double isotope technique employing quantitative autoradiography to identify the areas of brain that are differentially activated by the contiguous presentation of a conditioned and unconditioned stimulus and whether such heterosynaptic facilitation of neuronal activity can predict subsequent rates of learning. For example, the effect of some drugs on learning appear to be secondary to their ability to increase or decrease such heterosynaptic facilitation. Aim 3 will use intraventricular injections of drugs that activate or inhibit the cAMP system to examine the role of this second messenger in learning and in the effects of drugs on learning. Such knowledge should provide clues concerning the neural systems involved in human disorders of learning and memory (e.g., Alzheimer's disease) and identify the drugs that might be effective in their treatment.

Pavlovian conditioning of the rabbit's corneal-VIth nerve reflex involving extension of the nictitating membrane provides a reliable measure of the full range of associative learning and memory and has been demonstrated to be an excellent model system for examining the behavioral and pharmacological mechanisms by which drugs affect learning and memory. Associative learning, in particular, has been demonstrated to be highly sensitive to the actions of hallucinogenic drugs due to their ability to alter the sensory processing of the stimuli used during conditioning. Thus the indole hallucinogen d-lysergic acid diethylamide (LSD) and the phenethylamine hallucinogen 2,5- dimethoxy-4-methylamphetamine (DOM) produce changes in learning at doses required to produce reliable hallucinations in humans (1 and 50 Mu g/kg, respectively). Recently, two other penethylamine hallucinogens 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) have been demonstrated to produce apparently irreversible neurotoxicity to serotonin neurons. The basic purpose of the present studies is fivefold. First, to describe in detail the doses of MDA and MDMA required to alter the acquisition and retention of conditioned responses and identify the behavioral mechanisms through which the drugs exert their effects. Second, to determine whether the damage to serotonin neurons produced by MDA and MDMA results in a long-term deficit in learning and memory. Neurotoxic effects will be evaluated by histological methods and by measurement of monoamine content two to three weeks after cessation of drug treatment and by long-term changes in protein content of brain as measured by two-dimensional gel electrophoresis. Third, we will examine the ability of drugs such as serotonin antagonists and reuptake blockers to block the behavioral and neurotoxic effects of MDA and MDMA. Fourth, we will determine whether animals sustaining MDA and MDMA induced brain damage might be at risk with respect to subsequent impairment of serotonin, dopamine and cholinergic functions, as might occur during aging. Fifth, and last, we will carry out similar studies with LSD, DOM, d-amphetamine and d- methamphetamine to verify the specificity of our behavioral and neurotoxic effects. These studies should provide needed information on the growing population of humans that abuse these hallucinogenic agents and the long-term consequences of such abuse.

This is a proposal for a program project that would employ an animal model to investigate the consequences of fetal exposure to cocaine and the mechanisms by which observed deficits are produced. Recent clinical reports indicate that children born to cocaine-using women not only display a number of abnormalities as neonates but also demonstrate a number of behavioral abnormalities years later. The clinical symptoms that have been observed in such children suggest long-term disruption in the sensory processing of stimuli, cognitive abilities, emotionality and motor activity. Current knowledge of brain function suggests that the adequate. Expression of such behaviors requires the integrity of cortical, limbic and extrapyramidal structures. The pharmacology of cocaine suggests that it could have both direct and indirect effects on the development of these brain regions through actions on monoamines and opioid peptides. The possibility that the behavioral abnormalities might be due to measurable alterations in the structure and function of these brain regions will be examined in five interactive projects that will cover various developmental periods from mid-gestation to adulthood. Each project will test specific hypotheses that predict the occurrence of cocaine induced abnormalities as measured by behavioral, physiological, anatomical, pharmacological, neurochemical and molecular analyses. A core facility will be established to assure a consistent program of housing, breeding, administration of cocaine or vehicle to the pregnant dams, measurement of plasma and brain content of cocaine in dam and fetus, determination of any abnormalities in the neonate, cross fostering of neonates, paired feedings when appropriate, neurological and behavioral assessment of some developmental landmarks and adequate supply of animals at various ages. The exposure to cocaine and thus establish an animal model that be employed to develop method for the treatment and prevention of such abnormalities in children.

WPC> 2 B P Z Courier 10cpi #| x x 6 X @ 8 ; X @ HP LaserJet Series II HPLASEII.PRS x @ , t 0 )|X @ 2 2 B V P Z #| x Courier 10cpi 2 x x x , x @ 8 ; X @ HP LaserJet Series II HPLASER2.PRS x @ , t 0 vX @ 2 2 F ` < 9319709 Harvey & Abstract This research will investigate reactions of survivors in the Midwest to the floods in the summer of 1993. Respondents will be solicited via advertisements in newspapers and posted in community meeting places and contact with local agencies such as the Red Cross and mental health services. Responses will be gathered via telphone and mail surveys, interviews, written narratives about their losses, and diary record keeping from approximately 200 280 people living in Iowa, Illinois, Missouri, and Wisconsin. The subjects will reflect diversity in age, gender, race, socio economic status, urban rural home location, and occupation and who have experiences different kinds of loss as a result of the flooding. Subjects will include farmers, small business owners, non farmer/non business persons who were forced out of their homes by the flooding. A baseline comparison group will be people who lived in the region during the floods but who did not experience the loss of substantial physical property, jobs or income. During the next year, archival data will be gathered to assess the possible relationshops between people's experience of the flooding and the occurrences of events such as divorce, bankruptcy, and mental health visits.

The conference, Cocaine: Effects on the Developing Brain, is scheduled to take place in September, 1997, in Washington, D.C. The principal investigator and chair of the meeting is John A. Harvey, Ph.D., MCP Hahneman School of Medicine. The co-chair of the meeting will be Barry E. Kosofsky, M.D., Ph.D., Harvard University. The conference will bring together 250 pediatricians, child neurologists, developmental pediatricians, neuroscientists, special education consultants and public policy experts. The purpose of this meeting is to review the current understanding of how prenatal exposure of developing brain to cocaine alters program for brain development with consequence for brain structure, function and human development. An estimate done percent of infants born in the United States today are exposed to cocaine in utero. A recent convergence of clinical data with results obtained in preclinical (animal) models suggests the vulnerability of particular brain structures and neurotransmitter systems subserving particular brain functions, as well as evidence for compromise of more global CNS function following gestational cocaine exposure. In addition, recent clinical studies have identified environmental factors that affect developing human brain postnatally, which may alter the expression of brain insults sustained consequent to in utero cocaine exposure. Conference speakers will review what is known concerning the molecular, neurochemical, physiologic, and neuropathologic processes mediating the toxicity of gestational cocaine exposure, and will identify behavioral and clinical correlates of that exposure. The synthesis of clinical and preclinical data may inform scientists regarding common mechanisms underlying aspects of the toxicity of cocaine on the developing brain. It will foster a broader understanding of the problem for clinicians, as well as stimulate thinking regarding identification of relevant, selective therapeutic agents Models for effective intervention, and the implications for public policy will be discussed.

DESCRIPTION: (Applicant's Abstract) Our previous research, employing classical conditioning of the rabbit's nictitating membrane response has demonstrated that both associative learning and motor performance are critically dependent on the normal activity of the inferior olivary nucleus. Learning during classical conditioning involves a precise timing mechanism as indicated by its exquisite sensitivity to the temporal parameters of stimulus interval. Our work and that of others suggest that the synchronized oscillatory activity of olivary neurons may provide this timing mechanism. Moreover, serotonin (5-HT) has been demonstrated to regulate the rhythmic activity of the inferior olivary nucleus and also to determine the rate of learning and its motor expression. Both of these actions are mediated by the 5-HT2A receptor. Thus, we have hypothesize that 5-HT agonists and antagonists can increase or decrease the rate of learning and optimum level of motor function by acting at 5-HT2A receptors located on olivary neurons so as to enhance the ability of the olive to coordinate a neural network that determines the efficiency of learning and its motor expression. Experiments will be carried out to produce general or specific 5-HT denervations in order to assess the role of presynaptic 5-HT release on the acquisition of learning and motor performance. Systemic and intracerebral injections of 5-HT2A agonists and antagonists will allow us to identify the critical sites at which normal function can be restored. Other experiments will examine the 5-Ht mechanisms through which tremorogenic agents that act directly on the inferior olive impair learning and performance. Finally, we will examine whether the ability of some 5-HT2A antagonists to retard learning and motor function is due to their actions as inverse agonists. These experiments will provide clues concerning the role of the olivocerebellar system in learning and motor performance and possibly in the treatment of dysfunctions in learning and motor function. For example, 5-HT has been implicated in essential tremor and 5-HT2A receptor blockade has been demonstrated to be sufficient for antipsychotic action.

DESCRIPTION (provided by applicant): Increasing emphasis has been placed on the role of the serotonin 5-HT2A receptor in the pathogenesis of schizophrenia and affective disorders. In particular, the therapeutic effects of antipsychotic drugs have been suggested to be due to their actions at the 5-HT2A receptor that lead to changes in receptor density. However, the functional consequences of such receptor changes have not been fully examined. The innovative aspect of this proposal derives from: 1) our use of an animal model in which associative learning (a process that is abnormal in schizophrenia) is regulated by the 5-HT2A receptor, 2) our ability to detect changes in learning that result from alterations in the density of the 5-HT2A receptor in the adult brain, and 3) our preliminary evidence that the 5-HT2A receptor is constitutively active. We now propose to examine in detail how both the up- and down- regulation of the 5-HT2A receptor in limbic cortex, brain regions that are thought to be affected in schizophrenia, alters the rate of learning, the neuronal circuitry within those brain regions, the development of long-term potentiation (an in vitro model of learning), the constitutive activity of the receptor, and receptor mediated second messenger signaling. Learning is measured during classical trace conditioning of the rabbit's eye-blink response, a form of learning that is regulated by the 5-HT2A receptor, and is dependent on the integrity of limbic cortex (hippocampus and frontal cortex). It is important to note that eyeblink conditioning is also impaired in schizophrenia. Intracerebral injections of drugs will be used to identify the critical brain loci at which the 5-HT2A receptors regulate learning. Depletions of brain serotonin will be employed to determine the extent of constitutive activity at the 5-HT2A receptor as measured by basal and agonist stimulated second messenger signalling. The results of this research should provide novel therapeutic strategies in the treatment of schizophrenia. In addition, this research will provide a new perspective and new insights into the neurobiology of learning.