2011 — 2012 |
Saunders, Benjamin Thomas |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
Variation in the Abilty of Drug Cues to Reinstate Drug Seeking
DESCRIPTION (provided by applicant): Addicts have great difficulty resisting cues that have been associated with drug use. Such cues attract their attention, draw them to locations where drugs are located, and motivate continued drug-seeking behavior - often leading to relapse even in the face of an expressed desire to discontinue drug use. Drug cues are thought to acquire incentive motivational properties ("incentive salience") as a consequence of Pavlovian conditioning, whereby previously neutral stimuli acquire conditional stimulus (CS) properties. However, in preclinical studies using rats we have discovered that individuals vary markedly in the extent to which they attribute incentive salience to reward cues. A reward cue may act as a perfectly effective CS, evoking a conditional response (CR) in all animals, but function as a potent incentive stimulus only in some. Only if reward cues act as incentive stimuli do they come to attract, instigate, spur, and motivate, leading to potentially maladaptive behavior. I hypothesize, therefore, that individuals prone to attribute incentive salience to reward cues will have particular difficulty resisting them and will be especially vulnerable to relapse. Indeed, there is considerable variation in the ability of drug cues to instigate drug craving and relapse. Moreover, the degree that such cues increase the desire to take drug is correlated with how much the cue increases dopamine (DA) transmission. In the current application, I propose a series of preclinical studies to investigate individual variation in relapse behavior and its relationship with DA transmission (as measured using fast-scan cyclic voltammetry). This proposal will address the following questions: 1) Does individual variation in the tendency to attribute incentive value to reward cues predict variation in reinstatement to noncontingent drug cues? and 2) Do differences in phasic DA release encode variation in cue-induced reinstatement? These studies have the potential to significantly shift how we think about individual vulnerability to addiction and relapse, and point toward better-targeted interventions. PUBLIC HEALTH RELEVANCE: Addiction is a major public health problem in the United States, and the biggest threat to addicts is a high propensity to relapse. The goal of this project is to use a preclinical model to explore the psychological and neurobiological basis of individual variation in vulnerability to relapse, as this will help identify risk factors that will aid in the development of targeted interventions and treatments.
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0.961 |
2014 — 2016 |
Saunders, Benjamin Thomas |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Ventral Tegmental Area Dopamine in Cocaine Self Administration and Relapse @ University of California, San Francisco
DESCRIPTION (provided by applicant): Dopamine (DA) signaling has received considerable attention for its role in reward-related processes, including the motivation to seek drugs and relapse in response to drug-associated cues (1-4). Destruction of DA cells in the ventral tegmental area (VTA), or DA terminals in regions such as the nucleus accumbens, disrupts drug self-administration (5-6) and administration of DA receptor antagonists attenuates the ability of drug-associated stimuli to promote reinstatement (7). In human addicts, striatal DA release in response to drug-associated stimuli is associated with increased drug craving and future relapse (8,9). Though DA has been generally implicated in drug taking and relapse, DA systems have thus far not been manipulated with the temporal precision and cell-type specificity required to isolate their role in specific aspects of those behaviors. Optogenetic tools have been applied to target DA neurons in transgenic mice, demonstrating that DA signaling supports behavioral conditioning and facilitates instrumental responding for food (20-21). More recently, a Th:Cre transgenic ratline was developed that allows for the selective targeting of DA neurons with optogenetic methods (22-23) in more complex behavioral paradigms optimized for use in rats. In this proposal, I will utilize Th:Cre rats, incorporating in vivo optogenetics and electrophysiology in combination with sophisticated behavioral analyses, to probe the causal contribution of DA signaling to different aspects of instrumental cocaine intake and relapse in response to Pavlovian cocaine stimuli. First, in Aim 1 I propose to test the sufficiency of VTA DA neuron activation to modulate cocaine self-administration and cocaine cue-induced reinstatement. Second, in Aim 2 I propose to test the necessity of DA signaling, via inhibition of VTA DA neurons, for cocaine intake and reinstatement. Additionally, the VTA contains a heterogeneous mixture of not only DA neurons, but also a substantial fraction of non-DA neurons that contribute to motivational processing (11-19), but little is known about how different populations of neurons in the VTA encode drug-related behaviors. Thus, in Aim 3 I propose to characterize the firing patterns optogenetically-identified VTA DA neurons (16) during self-administration and reinstatement.
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1 |
2017 — 2020 |
Saunders, Benjamin Thomas |
K99Activity Code Description: To support the initial phase of a Career/Research Transition award program that provides 1-2 years of mentored support for highly motivated, advanced postdoctoral research scientists. R00Activity Code Description: To support the second phase of a Career/Research Transition award program that provides 1 -3 years of independent research support (R00) contingent on securing an independent research position. Award recipients will be expected to compete successfully for independent R01 support from the NIH during the R00 research transition award period. |
Midbrain Cellular and Circuit Dynamics of Cocaine Seeking @ Johns Hopkins University
Project Summary Addiction is a disorder of major public health concern, characterized by compulsive craving, drug seeking, and a high probability of relapse that is often spurred by the presence of drug-associated cues. Drug-induced changes in midbrain circuits, including the ventral tegmental area (VTA) and substantia nigra (SN), are thought to underlie these behaviors, but the heterogeneous mixture of neuronal subtypes and projections of the midbrain has prevented a clear understanding of the role of specific neurons and circuits in behavior. In previous studies, which utilized optogenetics methods to specifically manipulate midbrain dopamine neurons, I found a functional dissociation in the contribution of neurons projecting to the nucleus accumbens versus dorsal striatum in the motivational effects of conditioned cues, suggesting that reward processes are parcellated across anatomical divisions in the midbrain. Here, I expand on these findings to identify and compare the role of dopamine and GABA neurons in the VTA and SN in cocaine-evoked behaviors and relapse of cocaine seeking evoked by cocaine-associated cues. I will do so using state-of-the-art viral-based methods to visualize and manipulate neuronal activity. In the K99 Aims, I first propose to employ in vivo deep brain imaging to visualize the calcium dynamics of large numbers of dopamine and GABA neurons in the midbrain during cocaine exposure. Next, I propose to use chemogenetic methods, which rely on the insertion of designer receptors into target neurons, to tonically silence the activity of dopamine and GABA neurons to assess their functional role in behavioral sensitization to cocaine. These studies will define the cocaine-induced physiological responses of genetically defined VTA and SN neurons, and their role in cocaine-evoked behavior. Building on the new training and insights into the neurophysiological effects of cocaine I gain during the K99 period, I will utilize in vivo calcium imaging and optogenetics to determine to the activity patterns and temporal role of select midbrain projections in operant cocaine seeking and cue-triggered relapse during the R00 period. First, I will image activity of dopamine and GABA neurons projecting to the striatum or thalamus as animals seek cocaine and respond to cocaine-associated cues. Next, I will harness the temporal precision optogenetics to phasically manipulate these projections at discrete time points to determine their necessity and/or sufficiency for cocaine self-administration and cue-triggered relapse test. The proposed studies will provide a novel and comprehensive characterization of the circuit mechanisms by which midbrain neurons orchestrate cocaine and cocaine-cue related behaviors.
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0.958 |