Alan Swann - US grants

This ADAMHA Research Scientist Development Award, Type II, is sought in order to carry out research examining the relationship between energy metabolism and nerve activity and its regulation in affective disorders and alcoholism. The experimental model used will be (NA+, K+)-ATPase, the enzymatic mechanism of active cation transport and of stimulation-dependent energy metabolism in nerve, and its regulation by norepinephrine. The research will be based on my previous data describing the reaction mechanism of (Na+, K+)-ATPase, the possible presence of a nerve-specific form of enzyme, and the regulation of nerve-specific enzyme by noradrenergic innervation. Experiments on enzyme regulation and nerve activity in vivo will examine a) regulation by norepinephrine in terms of localization of regulated enzyme, specificity for nerve enzyme and for norepinephrine, and role in noradrnergic effects, b) methods of measuring nerve-specific enzyme, c) characterization of a possible endogenous sodium pump inhibitor and its interactions with norepinephrine, and d) physiology of the norepinephrine-ATPase system including peripheral-central interactions and role in energy balance. Experiments on regulation in vitro will examine the relationship between the energy of cation binding and cation transport and the effects on this of norepinephrine and electrical stimulation, and the relationship between (Na+, K+)-ATPase activity and energy production. Approaches to the study of this system in nerve cells will be developed using isolated cells from liver and from brown adipose tissue. The hypothesis being tested will be that nerve-specific enzyme is regulated by norepinephrine via cylic AMP. In clinical studies, red and white blood cell (Na+, K+)-ATPase and plasma levels of the inhibitor will be compared in normal, alcoholic, and depressed patients. Nerve-specific enzyme and norepinephrine stimulation will be compared using enzyme from postmortem brain samples from these groups. In the course of these studies, I will develop methods for measuring energy metabolism in isolated cells, measurement of ion transport in artificial vesicles, and measurement of membrane potentials in vitro.

The research in this proposal will examine the regulation of (Na+,K+)-ATPase in vivo by norepinephrine and by a specific endogenous inhibitor of the enzyme. (Na+,K+)-ATPase is the enzymatic basis of energy-dependent Na+ and K+ transport and has a central role in the regulation of intracellular cation concentrations and, hence, of membrane potential, cell excitability, and energy utilization. The experiments in this proposal are in four parts. 1) Experiments examining regulation of (Na+,K+)-ATPase, and interactions between norepinephrine and thyroid or adrenocortical hormones in regulation of (Na+,K+)-ATPase, and interactions between noradrenergic regulation of (Na+,K+)-ATPase and other mechanisms of Na+ Ca++ transport. 2) Experiments on specificity of transmitter regulation of (Na+,K+)-ATPase will examine specificity with respect to a) transmitter, receptor subtype, and tissue, b) molecular form of enzyme, using polyacrylamide gel electrophoresis to separate the two forms of enzyme, and c) localization of enzyme regulated by norepinephrine, using radioautography. The latter experiments will provide pilot data for development of studies using positron emission tomography. 3) Experiments on the mechanism of the noradrenergic effects will examine (Na+,K+)-ATPase-mediated transport in vitro. Initial experiments will compare effects in synaptosomes, dissociated brain cells, and brain slices. Further experiments will examine transmitter specificity, effects of prior exposure to norepinephrine, hormone status, or treatment with psychoactive drugs in vivo, effects of electrical stimulation in vitro, and roles of cation fluxes and of cyclic nucleotides. 4) Experiments in man will use stimulation of cation shifts by endogenous catecholamines to develop a means for examining noradrenergic regulation of (Na+,K+)-ATPase in intact man. These studies will provide the basis for studies of noradrenergic regulation of (Na+,K+)-ATPase in normal man and in conditions related to functions of the norepinephrine-(Na+,K+)-ATPase system, including affective disorders, eating disorders, and disorders of neural arousal.

These experiments are a continuation of our examination of the effects of ethanol on cation transport, the interaction between ethanol and norepinephrine in vivo, and the susceptibility to membrane effects in man. Na+,K+-ATPase has a central role in the regulation of cation gradients, membrane potential, cell excitability, and activity-linked energy metabolism in excitable cells. Ethanol alters regulation of Na+,K+-ATPase but there are no data about whether these effects are relevant to the changes in cell cation concentrations that accompany electrical activity. The studies will continue the previous work to examine the relationship between membrane effects of ethanol and the responses of cation transport to neural activity. The experiments will focus on four questions: 1) the locus of the ethanol effect on transport: the hypothesis is that ethanol affects internal cation binding sites that regulate Na+,K+-ATPase conformation. 2) Functional aspects of transport regulation as examined by effects on Na+/K+ selectivity of the internal cation sites and by stimulation of transport by increased cell Na+. 3) The interaction between norepinephrine and ethanol in terms of active cation transport and possible receptor-mediated changes in membrane properties. 4) Adaptation to effects of ethanol and norepinephrine in vivo. These experiments will examine functional aspects of cation transport and norepinephrine effects from selected experiments on questions 1)-3) in rats treated with chronic ethanol combined with direct noradrenergic stimulation or depletion. Effects on red blood cells will be compared to those on brain tissue, in order to determine the applicability of clinical material. These experiments will establish whether effects of ethanol on transport are likely to be relevant in vivo. If the effects are relevant, the results will provide the basis for studies of cation transport in alcoholism.

biomedical equipment purchase;

biomedical equipment purchase;

This is a proposal to study mechanisms of state-dependent change in impulsivity. Understanding of the mechanisms of short term changes in impulsivity will be important in designing means for diagnosis, monitoring, and treatment of the potentially destructive disorders where impulsivity is prominent or where even small changes in impulsivity may have dire consequences. Most existing knowledge concerns impulsivity as a stable trait rather than the near term likelihood of impulsive behavior. The overall hypothesis of this proposal is that state-dependent flucutations in impulsivity are related to changes in noradrenergic function and occur against the backgrand of stable trait-related impulsivity that may depend on serotonergic function. Bipolar disorder provides a model for state-dependent change since increased impulsivity is closely linked to the manic state. Antisocial personality provides a comparison group where impulsivity is less related to affective state. Norepinephrine and its neurophysiological effects are also increased in mania. Effects on event-related potentials provide an objective and readily available measure that is directly related to the CNS. Based on this model, we will investigate whether short term changes in impulsivity are related to changes in noradrenergic activity and its neurophpysiological consequences. State-related changes in impulsivity will be measured using behavioral laboratory methods that our group has developed. The Specific Aims are 1) to compare state and trait measures of impulsivity, noradrenergic function, and event-related potentials (sensory gating) in euthymic and manic subjects with bipolar disorder, subjects with antisocial personality disorder, and healthy control subjects, 2) to investigate effects of pharmacologically decreasing noradrenergic function with clonidine in manic subjects with bipolar disorder and in subjects with antisocial personality disorder, with the hypothesis that there will be parallel reductions in plasma MHPG, state-related impulsivity, and sensory gating impairment, 3) to investigate effects of pharmacologically increased noradrenergic activity by yohimbine in subjects with antisocial personality disorder and healthy controls, with the hypothesis that there will be parallel increases in the same parameters reduced in manic subjects by clonidine in AIM 2, and 4) in AIMS 2 and 3 we will investigate the relationship between baseline trait-like impulsivity and the sensitivity of impulsivity to changes in noradrenergic function. The results of these experiments may suggest means for monitoring risk for impulsive behavior and for a rational treatment schema for impulsivity.