1998 — 1999 |
Kirby, Lynn G |
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. |
Crf Effects in the Dorsal Raphe Nucleus @ McP Hahnemann University
stress; depression; corticotropin releasing factor; serotonin; dorsal raphe nucleus; hormone regulation /control mechanism; neuroregulation; disease /disorder model; neurochemistry; hormone receptor; psychological stressor;
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0.961 |
2006 — 2010 |
Kirby, Lynn G |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Serotonin Circuits in Opiate Addiction and Relapse @ Temple Univ of the Commonwealth
DESCRIPTION (provided by applicant): Opioids are highly effective in the clinical treatment of pain but sustained administration results in the development of tolerance and may lead to addiction. Even after prolonged abstinence, former addicts can remain vulnerable to relapse, particularly under stressful conditions. Much research on the neurobiological mechanisms of opiate addiction and relapse has focused on opioid regulation of dopaminergic reward pathways. Fewer studies have examined the role of the serotonin (5-hydroxytryptamine;5-HT) system in opiate addiction, particularly at the single cell level. The serotonin system may contribute to the affective components of addiction: both euphoric responses to opiates and dysphoric states during withdrawal. Dysregulation of the 5-HT system by long-term exposure to opiates may also underlie the high rate of comorbidity of affective disorders such as depression with opiate dependence. In addition, the 5-HT system regulates dopaminergic neurotransmission, thus may indirectly play a role in more traditional reward pathways. The objective of this application is to test the hypothesis that the serotonergic dorsal raphe nucleus (DRN) is regulated by opioids and stress and furthermore that this neural circuit is a substrate for stress-induced opiate relapse. This objective will be achieved using a combination of electrophysiological, immunohistochemical, pharmacological and behavioral techniques. AIM 1 will compare the effects of the stress neurohormone corticotropin-releasing factor (CRF) and morphine on GABA- and glutamatergic synaptic activity in 5-HT DRN cells in vitro. Next, the role of DRN circuits in stress-induced morphine relapse will be investigated using electrophysiological (AIM 2) and behavioral (AIM 3) models. These studies will characterize the DRN as an integrator of inputs from multiple neurotransmitter pathways that are engaged by both opioids and stress to impact 5-HT neurotransmission. These studies may also identify novel targets for the treatment of opiate addiction and the prevention of relapse. Opiate addiction and relapse are significant public health concerns. This proposal aims to investigate the neurobiological basis for these conditions from single cell physiology to behavioral levels. This approach may identify novel targets for the treatment of opiate addiction and the prevention of relapse.
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1 |
2014 — 2015 |
Kirby, Lynn G |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Gabaergic Sensitization of the Serotonin System in Stress-Induced Opiate Relapse @ Temple Univ of the Commonwealth
DESCRIPTION (provided by applicant): Opioids are effective analgesics but also carry a high abuse liability. Even after prolonged abstinence, former opioid addicts can remain vulnerable to relapse, particularly under stressful conditions. Most of the focus on opioid addiction and relapse mechanisms have centered on traditional dopaminergic reward pathways. Fewer studies have examined the role of the serotonin (5-hydroxytryptamine; 5-HT) system in opioid addiction and relapse. Preliminary data in rodents indicate that stress interacts with opioid history to sensitize 5-HT dorsal raphe nucleus (DRN) neurons to GABAergic inhibition. More recent work identified a causal relationship between GABA signaling in the DRN and stress-induced opioid reinstatement. We hypothesize that this GABAergic sensitization results in serotonergic hypofunction and consequent dysphoric mood states which drive drug-seeking behaviors and therefore confer vulnerability to stress- induced opioid relapse. In the current application, we will employ two state-of-the-art genetic mutational strategies using the Cre-loxP system to engineer mice that are deficient in GABAA receptors selectively in the DRN or specifically in 5-HT neurons. First, we will confirm DRN- or 5-HT-specific deletion of the GABAA receptor in these mice using immunohistochemistry, electrophysiology and quantitative autoradiography. Next, we will test these mice in two complementary animal models of relapse in which a swim stress is used to reinstate previously extinguished morphine conditioned place-preference or self-administration. We predict that these mice will be protected from the GABAergic sensitization observed in the 5-HT DRN system following a stress-induced relapse model and will thus be less vulnerable to relapse in these two models. These studies will generate innovative animal models of opiate relapse resistance that will be a valuable tool to elucidate novel circuitry within the 5-HT DRN system that contribute to opiate relapse. This approach may identify novel targets for the treatment of opiate addiction and the prevention of relapse.
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0.928 |
2019 — 2021 |
Kirby, Lynn G |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of 5-Ht Circuits by Crf and Gaba in Opioid Addiction and Stress-Induced Relapse @ Temple Univ of the Commonwealth
Stress impacts multiple phases of opioid addiction and is associated with greater vulnerability to initiation of drug taking, more rapid transition from drug use to abuse, and higher rates of drug relapse, though the neural circuitry and mechanisms involved are largely unknown. A growing literature indicates the involvement of the dorsal raphe nucleus (DRN)-serotonin (5-hydroxytryptamine; 5-HT) system in some of the affective components of drug addiction that motivate drug taking and relapse. Acute opioids stimulate 5-HT neurotransmission via GABAergic disinhibition, potentially contributing a positive affective component to the motivation for drug seeking early in opioid addiction. By contrast, later in addiction, the 5-HT DRN system may also contribute to drug-seeking motivated by negative affect via its responsiveness to stressors and its interaction with the corticotropin-releasing factor (CRF) system. Our laboratory and others have shown that CRF-R1 receptors inhibit 5-HT DRN neurons via GABA interneurons. Preliminary data indicate a novel neuroadaptation within DRN-CRF circuits that is associated with vulnerability to stress-induced opioid relapse. Rats expressing extinction of either heroin intravenous self-administration (IVSA) or morphine conditioned place-preference (CPP) that are exposed to stress reinstate their previously extinguished heroin-seeking behavior or morphine CPP, an effect accompanied by sensitization of GABAA receptors on 5-HT DRN neurons. This neuroadaptation would render 5-HT DRN neurons vulnerable to inhibition by CRF-R1-GABA inputs. From these collective data, we hypothesize a dual role for the 5-HT system in opioid addiction: 1) early opioid exposure stimulates 5-HT DRN neurons, creating a positive affective state that contributes to opioid reward; 2) stress exposure in subjects with an opioid history sensitizes GABAA receptors on 5-HT DRN neurons, making them vulnerable to inhibition by CRF-R1 located on GABA afferents. The resulting 5-HT hypofunction creates a negative affective state that motivates opioid reinstatement. In specific aim 1, we will use electrophysiology to measure the dynamic changes in membrane properties and excitability of 5-HT DRN neurons ex vivo as they track with changes in affect and behavior over the course of a rat model of heroin IVSA, extinction and stress- induced reinstatement. In specific aim 2 we will use viral delivery of Designer Receptor Exclusively Activated by Designer Drugs in Tph2-Cre rats to examine the impact of manipulating 5-HT DRN neuronal activity in vivo in the behavioral model. In specific aim 3 we will use viral delivery of DREADDs in Crh-Cre or GAD-Cre rats to test the causal relationship between amygdala CRF afferents to the DRN and DRN GABA interneurons in the behavioral model. This proposal employs multiple ex vivo and in vivo approaches to dissect the role of 5-HT- GABA-CRF circuitry in a model of opioid addiction and relapse with the ultimate goal of identifying novel therapeutic targets to treat opioid addiction and prevent relapse.
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0.928 |