Patricia Shinnick-Gallagher - US grants

The proposed research is designed to obtain a basic understanding of the electrophysiology, pharmacology and morphology of mammalian parasympathetic ganglia and to define the local neuronal interactions which contribute to the integrative function of autonomic ganglia, in general. Local neuronal interactions which occur during ganglionic transmission will be analyzed in cat vesical pelvic ganglia (VPG) using intracellular, single electrode voltage clamp, and iontophoretic techniques coupled with differential interference microscopy. The following local neuronal interactions will be investigated in mammalian parasympathetic ganglia 1) the muscarinic inhibitory and excitatory slow synaptic potentials 2) the late slow modulatory potentials 3) synaptic events underlying synaptic plasticity, 4) intrinsic cell-to-cell communication and 5) the neurotransmitter/neuromodulatory role of leucine-enkephalin. The sites, mechanisms and functional significance of the local neuronal interactions which occur in bladder ganglia will be determined. Analysis of the mechanisms underlying these local neuronal interactions may lead to a better understanding of autonomic function, in general, as well as "higher" brain functions involved in memory, learning, and behavior. In addition, the information obtained from pharmacologicaly analysis of these synaptic mechanisms may eventually result in use of drugs which are more clinically effective in the treatment of CNS disorders, in particular, Parkinson's Disease as well as autonomic dysfunction, especially, bladder dysfunction.

The long term objective of this research is to characterize transmission through cat bladder parasympathetic ganglia and thereby to define the local neuronal interactions which may contribute to the integrative function of autonomic ganglia and to higher CNS functions involved in memory and learning. Information derived from this research would enhance our understanding of the neural control of the urinary bladder and its physiology and pharmacology. Local neuronal interactions which occur during ganglionic transmission will be analyzed in cat parasympathetic ganglia of the urinary bladder using intracellular, single and double electrode voltage clamp and single channel- patch clamp analysis. The local neuronal interactions which will be analyzed in this proposal are endogenously occurring synaptic events mediated by three different neurotransmitters, namely, acetylcholine (ACh), norepinephrine (NE) and adenosine. Evidence suggests that all three of these endogenous neurotransmitter mediated hyperpolarizing synaptic potentials are mediated by a calcium dependent potassium conductance. The outward K currents underlying the sow inhibitory synaptic potentials in cat bladder parasympathetic ganglia will be analyzed as well as pharmacological charcteristics of and possible second messenger systems underlying the synaptic responses mediated by the neurotransmitters, acetylcholine, norepinephrine, and adenosine. In addition the membrane K channels activated by ACh, NE, and adenosine wil be compared with the properties of Ca-activated K channels located in the membranes of cat bladder parasympathic neurons. The above studies should provide essential information about the membrane mechanisms involved in neuronal communication between pre- and post-synaptic neurons, and about possible mechanisms linking electrophysiological events with intracellular second messengers and cell metabolism. Analysis of the mechanisms underlying these local neuronal interactions may lead to a better understanding of autonomic function, as well as "higher" brain functions involved in memory, learning, and behavior. In addition, the information obtained form pharmacological analysis of these synaptic mechanisms may eventually result in the use of drugs which are more clinically effective in the treatment of CNS disorders, as well as autonomic dysfunction, particularly, bladder dysfunction.

DESCRIPTION (Adapted from Applicant's Abstract): Complex partial seizures are the most common type of epileptic syndrome and the most drug resistant. Kindling is a model of complex partial seizures. The long-term objective of this research is to determine the membrane mechanisms underlying the long-lasting changes in the basolateral amygdala resulting from kindling-induced epileptogenesis. We have shown that the kindling profound long-lasting changes occur in metabotropic glutamate receptor (mGluR)-mediated responses in the amygdala. We will define the subtypes of mGluRs and their coupled second messenger effectors that are altered in kindling and test the hypothesis a) that mGluRs affecting kindling-induced bursting are different from those modifying epileptiform bursting in acute models of epilepsy and b) that the changes within mGluR subgroups recorded in kindled neurons are mediated through specific mGluR subtypes. We will use amygdala brain slice preparations from control animals and animals kindled in vivo using intracellular sharp and whole cell patch electrode recording and antisense oligodeoxynucleotide technology (ODN) to address the following specific aims: 1) Characterize the second messenger effectors of the mGluR-mediated responses that have been found to be altered in kindled neurons. 2) Compare pharmacological agonists and antagonists of the subtypes of mGluRs modifying epileptiform bursting in kindled neurons with those affecting the induction and maintenance of epileptiform bursting in acute models of epilepsy. 3) Analyze using anti-sense ODNs the specific subtypes of mGluR underlying mGluR agonist-induced responses, the induction and maintenance of epileptiform bursting in acute models of epilepsy, and epileptiform bursting in kindled neurons. Elucidating the subtypes of mGluRs and their respective second messenger effectors and identifying agonists and antagonists of mGluRs which modify epileptiform bursting in acute models of epilepsy and in kindling will enhance our understanding of the mechanisms underlying epileptogenesis in the amygdala and ultimately to evolve more effective therapies for the treatment of complex partial seizures.

DESCRIPTION (adapted from applicant's abstract): The amygdala is known to play a critical role in emotional responses particularly fear, in both humans and animals. The amygdala and its afferent and efferent connections comprise a major component of the auditory fear conditioning circuitry. The long-term objective of this research is to characterize pre- and postsynaptic modifications in amygdala glutamatergic neurotransmission underlying the expression of learned fear. Preliminary data show significant alterations in synaptic transmission in the internal capsule (IC) fiber pathway from the medial geniculate to the dorsal lateral amygdala recorded in vitro in amygdala slices from paired fear conditioned but not unpaired control animals. The proposed experiments using the fear-potentiated startle paradigm will test the hypothesis that lasting potentiation of synaptic transmission occurs at particular synapses within the fear conditioning intraamygdala circuitry. The following specific aims will be addressed using whole cell patch recording in amygdala slice preparations from three populations of animals. naive control, unpaired control and paired fear conditioned animals: 1) Characterize the modifications in synaptic transmission and membrane conductance underlying fear conditioning and determine the pre- and post-synaptic changes in N-methyl-D-aspartate (NMDA)- and non-NMDA-mediated synaptic transmission in animals exposed to a paired conditioned stimulus (CS) and aversive stimulus (UCS) with those exposed to the same information but in an unpaired paradigm and 2) trace the information flow through the amygdala by comparing in the three populations of animals the synaptic modifications occurring in glutamatergic transmission at different synapses in the amygdala fear conditioning circuitry. The results of the proposed experiments will enhance our understanding of the membrane mechanisms underlying emotional learning at the membrane and whole cell level and provide important information about changes in the essential elements of interneuronal communication within a key structure involved in emotion, the amygdala. Ultimately the proposed studies may provide insight into potential therapeutic strategies in the treatment of neuropsychiatric disorders such as anxiety, phobia, schizophrenia and in particular posttraumatic stress disorder.

DESCRIPTION (provided by applicant): The amygdala is a brain area that has recently become one of the hottest topics in neuroscience. Interest in the amygdala is not limited to scientists but also includes the general public and business professionals who are actively seeking more information about the brain machinery governing emotions that control our coping with ongoing everyday life and impact on social signaling. The objective of this meeting is to provide a forum for presenting cutting edge information on the basic characteristics of amygdala function from neuroanatomical, electrophysiological, behavioral, and imaging studies in animals and humans and to integrate that data with the most recent findings in clinical human diseases in which the function of the amygdala is compromised. The desired outcome of the conference is to discuss and perhaps even to reach consensus on the important issues facing the field which impact on our basic understanding of amygdala function. Top experts in the field will meet together for 2.5 days (March 23-26, 2002) at Moody Gardens on Galveston Island, Texas, to discuss the important issues shaping our basic understanding of amygdala function. In plenary presentations and in discussions, critical questions regarding amygdala function at a basic and clinical level will be addressed. Specifically: 1. What is the functional significance of the specific nuclei of the amygdala? Can we use the term "amygdala" to attribute function to these brain areas? Does functional homogeneity between amygdala nuclei exist? Is the "extended" amygdala an anatomical or functional concept? How relevant is this definition for your results? 2. Is the amygdala a critical part of the neuronal circuitry for stimulus-reward associations? 3. Do drugs act at different sites in the amygdala to affect specific behaviors? Sessions will also address such issues as the nuclear structure and nomenclature of the amygdala between different species that is critical for extrapolation of data, for example, from rat/monkey studies to human studies as well as the organization of inhibition and excitation in the amygdala and the breadth of emotions controlled by the amygdala. Other important questions concern whether the amygdala is an integrator or repositor of memories and the role of the amygdala in withdrawal from drugs of abuse. The clinical implications of these functions will be addressed by discussion of symptomatology caused by amygdala damage in Alzheimer's disease and epilepsy and its function in mental illness including anxiety, depression, schizophrenia, and panic disorder. Throughout these discussions, pharmacological information will be presented to provide a foundation for designing drugs for treatment of amygdala pathology. Conference proceedings will be published as a volume of the Annals of the New York Academy of Sciences.

DESCRIPTION (provided by applicant): The amygdala, part of the brain reward circuitry, plays a role in cocaine-seeking and withdrawal in animals and craving and relapse in humans. The incentive motivation for cocaine is associated with cocaine cues and the amygdala is essential in forming drug-related associations. The membrane effects of chronic cocaine on amygdala neurons, however, are not known and mechanisms underlying drug-related associations are only beginning to be understood. The long-term objective of this research is to analyze the mechanisms underlying cocaine cue-related information by characterizing the modulation and modification of amygdala neurotransmission at the synaptic level during withdrawal from chronic cocaine. Chronic cocaine enhances glutamatergic transmission and group I metabotropic glutamate receptor (mGluR) effects in amygdala neurons. Dopamine also plays a role in cue related events in the amygdala. The proposed experiments will test the hypothesis that 2 weeks after withdrawal from chronic cocaine persistent alterations of neurotransmission and plasticity are specific for amygdala pathways and modulated by metabotropic glutamate and dopaminergic receptors. In these experiments synaptic transmission in intra-amygdala pathways is recorded using sharp electrode, whole cell patch, and extracellular recording in amygdala slices. The overall goal is to analyze membrane measures of cue-associated cocaine memory after chronic cocaine withdrawal, specifically: 1. Characterize the modifications in glutamatergic synaptic transmission and plasticity to stimuli representing drug-related cues and determine the underlying signaling mechanisms during chronic cocaine withdrawal; 2. Analyze the role of metabotropic glutamate and dopamine receptors in modulating synaptic transmission and plasticity and determine the underlying signaling mechanisms after withdrawal from chronic cocaine. These studies will determine synaptic mechanisms underlying neuroadaptations and intra-amygdala communication of drug-related cues after chronic cocaine withdrawal and may lead to novel and more rational strategies to block cue-induced relapse of cocaine addiction.