IU Indianapolis ScholarWorks :: Browsing by Author "Johnson, Philip L."

Browsing by Author "Johnson, Philip L."

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Angiotensin-II is a putative neurotransmitter in lactate-induced panic-like responses in rats with disruption of GABAergic inhibition in the dorsomedial hypothalamus
(Society for Neuroscience, 2006-09-06) Shekhar, Anantha; Johnson, Philip L.; Sajdyk, Tammy J.; Fitz, Stephanie D.; Keim, Stanley R.; Kelley, Pamela E.; Gehlert, Donald R.; DiMicco, Joseph A.; Psychiatry, School of Medicine
Intravenous sodium lactate infusions or the noradrenergic agent yohimbine reliably induce panic attacks in humans with panic disorder but not in healthy controls. However, the exact mechanism of lactate eliciting a panic attack is still unknown. In rats with chronic disruption of GABA-mediated inhibition in the dorsomedial hypothalamus (DMH), achieved by chronic microinfusion of the glutamic acid decarboxylase inhibitor L-allylglycine, sodium lactate infusions or yohimbine elicits panic-like responses (i.e., anxiety, tachycardia, hypertension, and tachypnea). In the present study, previous injections of the angiotensin-II (A-II) type 1 receptor antagonist losartan and the nonspecific A-II receptor antagonist saralasin into the DMH of "panic-prone" rats blocked the anxiety-like and physiological components of lactate-induced panic-like responses. In addition, direct injections of A-II into the DMH of these panic-prone rats also elicited panic-like responses that were blocked by pretreatment with saralasin. Microinjections of saralasin into the DMH did not block the panic-like responses elicited by intravenous infusions of the noradrenergic agent yohimbine or by direct injections of NMDA into the DMH. The presence of the A-II type 1 receptors in the region of the DMH was demonstrated using immunohistochemistry. Thus, these results implicate A-II pathways and the A-II receptors in the hypothalamus as putative substrates for sodium lactate-induced panic-like responses in vulnerable subjects.
Anxiogenic CO2 Stimulus Elicits Exacerbated Hot Flash-like Responses in a Rat Menopause Model and Hot Flashes in Menopausal Women
(Lippincott, Williams & Wilkins, 2016-11) Federici, Lauren M.; Roth, Sarah Dorsey; Krier, Connie; Fitz, Stephanie D.; Skaar, Todd C.; Shekhar, Anantha; Carpenter, Janet S.; Johnson, Philip L.; Anatomy and Cell Biology, School of Medicine
Objective Since longitudinal studies determined that anxiety is a strong risk factor for hot flashes, we hypothesized that an anxiogenic stimulus that signals air hunger (hypercapnic, normoxic gas) would trigger an exacerbated hot flash-associated increase in tail skin temperature (TST) in a rat ovariectomy (OVEX) model of surgical menopause and hot flashes in symptomatic menopausal women. We also assessed TST responses in OVEX serotonin transporter (SERT)+/− rats that models a common polymorphism that is associated with increased climacteric symptoms in menopausal women and increases in anxiety traits. Methods OVEX and sham-OVEX rats (initial experiment) and wildtype and SERT+/− OVEX rats (subsequent experiment) were exposed to a 5 min infusion of 20%CO2 normoxic gas while measuring TST. Menopausal women were given brief 20% and 35%CO2 challenges, and hot flashes were self-reported and objectively verified. Results Compared to controls, OVEX rats had exacerbated increases in TST, and SERT+/− OVEX rats had prolonged TST increases following CO2. Most women reported mild/moderate hot flashes after CO2 challenges, and the hot flash severity to CO2 was positively correlated with daily hot flash frequency. Conclusions The studies demonstrate that this anxiogenic stimulus is capable of inducing cutaneous vasomotor responses in OVEX rats, and eliciting hot flashes in menopausal women. In rats, the severity of the response was mediated by loss of ovarian function and increased anxiety traits (SERT+/−), and, in women, by daily hot flash frequency. These findings may provide insights into anxiety related triggers and genetic risk factors for hot flashes in thermoneutral environments.
Assessment of Ethanol and Nicotine Interactions in the Rat Model: Pharmacotherapeutics, Adolescence, and the Mesolimbic System
(2019-09) Waeiss, Robert Aaron; Truitt, William A.; Hudmon, Andy; Johnson, Philip L.; McBride, William J.; Rodd, Zachary A.
Alcohol use disorder (AUD) and nicotine dependence often result in serious health problems and are top contributors to preventable deaths worldwide. Co-addiction to alcohol and nicotine is the most common form of polysubstance abuse. Epidemiological studies indicate that more than 80% of individuals diagnosed with AUD concurrently use nicotine. The prevalence of alcohol and nicotine comorbidity may stem from interconnected mechanisms underlying these disorders. A better understanding of how these drugs interact and the biological basis behind the high comorbidity rates could generate key targets for the development of more effective treatments for AUD and nicotine dependence. The following experiments utilized four similar overall groups consisting of vehicle, ethanol (EtOH), nicotine (NIC), and EtOH+NIC. Chapter Two investigated the efficacy of naltrexone and varenicline, the pharmacological ‘gold standards’ for treating AUD and nicotine dependence, on voluntary drug intake by rats selectively bred for high EtOH drinking. The results indicated that the standard treatments for AUD and nicotine dependence were effective at reducing consumption of the targeted reinforcer but neither reduced EtOH+NIC co-use/abuse. Chapter Three examined the effects of peri-adolescent EtOH drinking on the ability of NIC infused into the posterior ventral tegmental area (pVTA) to stimulate dopamine release within the nucleus accumbens (NAc) shell during adulthood. The results suggest a cross-sensitization to NIC produced by peri-adolescent EtOH consumption demonstrated by a leftward and upward shift in the dose response curve. Chapter Four investigated the effects of intra-pVTA infusions on NAc shell neurochemistry, EtOH reward within the NAc shell, and the role of brain-derived neurotrophic factor (BDNF) on EtOH reward within that region. The data indicated that only EtOH+NIC significantly increased glutamate, dopamine, and BDNF in the NAc shell. Repeated pretreatment with EtOH+NIC also enhanced EtOH reward in the NAc shell and BDNF infusions were sufficient to recapitulate these findings. Collectively, the data indicate that concurrent exposure to EtOH and NIC results in unique neuroadaptations that promote future drug use. The failure to develop effective pharmacotherapeutics for AUD or nicotine dependence could be associated with examining potential targets in models that fail to reflect the impact of polydrug exposure.
Assessment of fear and anxiety associated behaviors, physiology and neural circuits in rats with reduced serotonin transporter (SERT) levels
(Springer Nature, 2019-01-22) Johnson, Philip L.; Molosh, Andrei I.; Federici, Lauren M.; Bernabe, Cristian; Haggerty, David; Fitz, Stephanie D.; Nalivaiko, Eugene; Truitt, William; Shekhar, Anantha; Anatomy and Cell Biology, IU School of Medicine
Genetic variation in serotonin transporter (SERT) that reduces transcriptional efficiency is associated with higher anxiety and fear traits and a greater incidence of post traumatic stress disorder (PTSD). Although previous studies have shown that rats with no expression of SERT (SERT-/-) have increased baseline anxiety behaviors, SERT+/- rats with low SERT expression (and more relevant to the clinical condition with low SERT expression) do not. Yet, no systematic studies of fear acquisition/extinction or their underlying neural mechanisms have been conducted in this preclinical genetic SERT+/- model. Here we sought to determine if SERT+/- or SERT-/-, compared to wildtype, rats would show exacerbated panic responses and/or persistent conditioned fear responses that may be associated with PTSD or phobia vulnerability. Results: Only SERT-/- rats showed increased baseline anxiety-like behaviors with heightened panic respiratory responses. However SERT+/- (also SERT-/-) rats showed enhanced acquisition of fear and delayed extinction of fear that was associated with changes in serotonergic-related genes (e.g., reduced 5-HT1A receptor) and disrupted inhibition within the basolateral amygdala (BLA). Furthermore, the disrupted fear responses in SERT+/- rats were normalized with 5HT1A antagonist infusions into the BLA. Enhanced acquisition and failure to extinguish fear memories displayed by both SERT-/- and SERT+/- rats are cardinal symptoms of disabling anxiety disorders such as phobias and PTSD. The data here support the hypothesis that reduced SERT function is a genetic risk that disrupts select gene expression and network properties in the amygdala that could result in vulnerability to these syndromes.
Conditioned stimuli affect ethanol-seeking by female alcohol-preferring (P) rats: the role of repeated-deprivations, cue-pretreatment, and cue-temporal intervals
(Springer, 2019-05-16) Hauser, Sheketha R.; Deehan, Gerald A.; Knight, Christopher P.; Waeiss, Robert A.; Truitt, William A.; Johnson, Philip L.; Bell, Richard L.; McBride, William J.; Rodd, Zachary A.; Psychiatry, School of Medicine
Rationale: Evidence indicates drug-paired stimuli can evoke drug-craving leading to drug-seeking and repeated relapse periods can influence drug-seeking behaviors. Objectives: The present study examined (1) the effect of an interaction between repeated deprivation cycles and excitatory conditioning stimuli (CS +) on ethanol (EtOH)-seeking; (2) the effects of EtOH-paired cue-exposure in a non-drug paired environment on subsequent conditioning in a drug-paired environment; and (3) the temporal effects of conditioned cues on subsequent EtOH-seeking. Methods: Adult female alcohol-preferring (P) rats were exposed to three conditioned odor cues; CS+ associated with EtOH self-administration, CS- associated with the absence of EtOH (extinction training), and a neutral stimulus (CS0) presented in a neutral non drug-paired environment. The rats underwent 4 deprivation cycles or were Non-Deprived, following extinction they were maintained in a home cage for an EtOH-free period, and then exposed to no cue, CS+, CS-, or CS0 to assess the effect of the conditioned cues on EtOH-seeking behavior. Results: Repeated deprivations enhanced and prolonged the duration of CS+ effects on EtOH-seeking. Presentation of the CS- in a non-drug paired environment blocked the ability of a CS+ to enhance EtOH-seeking in a drug-paired environment. Presentation of the CS+ or CS- in a non-drug paired environment 2 or 4-hours earlier significantly altered EtOH-seeking. Conclusion: Results indicated an interaction between repeated deprivation cycles and CS+ resulted in a potentiation of CS+ evoked EtOH-seeking. In addition, a CS- may have therapeutic potential by providing prophylactic protection against relapse behavior in the presence of cues in the drug-using environment.
Developing a Rodent Model of Adverse Menopausal Symptoms
(Office of the Vice Chancellor for Research, 2011-04-08) Snow, Winter; Federi, Lauren; Fitz, Stephanie; Janasik, Stephen; Penno, Daniel; Samuels, Brian; Carpenter, Janet; Skaar, Todd C.; Shekhar, Anantha; Johnson, Philip L.
Menopause is a condition where severe depletion of estrogen levels leads to a cluster of adverse symptoms such as anxiety, cutaneous vasodilation/sudomotor "hot flashes", sleep disturbances, and appetite change (Freeman et al., 2005; Seritan et al., 2010). Previously, estrogen replacement therapy was the first line treatment for menopausal symptoms. However, it is no longer acceptable due to increased risk of cancer (Rossouw et al., 2002). Therefore there is a need for creating non-hormonal therapies to reduce the incidence of adverse menopausal-related symptoms. This is hindered by the limited understanding of menopausal symptoms and a lack of animal models of "hot flashes" (Nelson et al., 2006). Currently, the most accepted model of hot flashes is addicting female rats to morphine then inducing morphine withdrawal using naloxone (a ?-opioid receptor competitive antagonist) to provoke increases in tail temp (an indicator of cutaneous vasodilation). Yet, there is no evidence that the opioid system is disrupted in women with menopause [e.g., naloxone does not provoke "hot flashes" clinically (DeFazio et al., 1984)]. Here we induced a menopausal state by surgically removing the ovaries (OVEX) to deplete estrogen which induces a cluster of adverse menopause-like symptoms that include: 1) increased anxiety; 2) weight gain; and 3) disrupted diurnal skin and core body tempature changes. Additionally, we have developed an alternative model of "hot flashes" where administering yohimbine (an alpha2-adrenergic autoreceptor antagonist that provokes "hot flashes in menopausal women) resulted in "hot flash"-related increases in skin temp in OVEX, but not sham-OVEX, female rats.
Dissecting the Functional Heterogeneity of Serotonergic Systems That Regulate Fear and Panic
(2019-10) Setubal Bernabe, Cristian; Cummins, Theodore R.; Engelman, Eric; Johnson, Philip L.; Truitt, William A.
Serotonin (5-HT) is heavily implicated in severe anxiety and trauma-related disor-ders, such as panic and post-traumatic stress disorders. Overall, site-specific pharmacolog-ical manipulations show that while 5-HT enhances anxiety-associated/avoidance behaviors in the amygdala, 5-HT inhibits panic-associated escape behaviors in the perifornical hypo-thalamus region (PeFR). Yet, our understanding of how specific serotonergic networks and co-transmitters regulate these conditions, but also other aspects of innate panic (e.g., car-dioexcitation or thermal response that occur during a flight or escape response) or condi-tioned fear behaviors is still elusive. Therefore, utilizing circuit-based gain- and loss-of-function approaches to selectively manipulate amygdala- and PeFR-projecting sero-tonergic systems, we hypothesize that specific serotonergic networks projecting to the amygdala and PeFR respectively enhance conditioned fear responses and attenuate innate panic-associated behaviors and physiological responses. There are two main chapters in this dissertation. In Chapter III, retrograde tracing revealed that the amygdala-projecting neurons from dorsal Raphe (DR) were almost exclusively serotonergic (92-95%) concen-trated in the dorsal/ventral (DRD/DRV) DR, with few non-serotonergic neurons. While selective lesioning of this network with saporin toxin (SAP) facilitated the extinction of conditioned fear behavior, selective optogenetic activation of amygdala-projecting DRD/DRV cell bodies using intersectional genetics reduced extinction of conditioned fear behavior and enhanced anxiety avoidance. In Chapter IV, retrograde tracing showed that the PeFR was innervated by equally selective serotonergic networks concentrated in the lateral wings DR (lwDR) and median Raphe (MR). Contrasting with the results from the amygdala-innervating 5-HT system, lesioning the PeFR-projecting serotonergic network from lwDR/MR was accompanied by reduced extinction of conditioned fear behavior, in-creased anxiety avoidance, and increased CO2-induced panic (elevated escape responses and enhanced cardioexcitation). Conversely, selective activation of lwDR/MR serotonergic terminals in the PeFR decreased anxiety-associated behaviors; inhibited CO2-induced panic, and induced unconditioned and conditioned place preferences. The circuit-based ap-proach data presented here show that amygdala- and PeFR-projecting 5-HT neurons com-prise distinct circuits underlying opposite roles enhancing anxiety/fear responses in the amygdala and dampening fear/panic responses in the PeFR. The identification of distinct circuits controlling anxiety, fear, and panic responses is a fundamental step towards the development of more effective therapies for psychiatric conditions such as anxiety and trauma-related disorders.
Dual Orexin Receptor Antagonist Attenuates Increases in IOP, ICP, and Translaminar Pressure Difference After Stimulation of the Hypothalamus in Rats
(Association for Research in Vision and Ophthalmology, 2022) DeCarlo, Arthur A.; Hammes, Nathan; Johnson, Philip L.; Shekhar, Anantha; Samuels, Brian C.; Ophthalmology, School of Medicine
Purpose: Intraocular pressure (IOP) remains the only modifiable risk factor for glaucoma progression. Our previous discovery that stimulation of nuclei within the hypothalamus can modulate IOP, intracranial pressure (ICP), and translaminar pressure difference (TLPD) fluctuations led us to investigate this pathway further. Our purpose was to determine the role of orexin neurons, primarily located in the dorsomedial hypothalamus (DMH) and perifornical (PeF) regions of the hypothalamus, in modulating these pressures. Methods: Sprague Dawley rats were pretreated systemically with a dual orexin receptor antagonist (DORA-12) at 30 mg/Kg (n = 8), 10 mg/Kg (n = 8), or vehicle control (n = 8). The IOP, ICP, heart rate (HR), and mean arterial pressure (MAP) were recorded prior to and following excitation of the DMH/PeF using microinjection of the gamma-aminobutyric acid (GABA)A receptor antagonist bicuculline methiodide (BMI). Results: Administration of the DORA at 30 mg/Kg significantly attenuated peak IOP by 5.2 ± 3.6 mm Hg (P = 0.007). During the peak response period (8-40 minutes), the area under the curve (AUC) for the 30 mg/Kg DORA cohort was significantly lower than the control cohort during the same period (P = 0.04). IOP responses for peak AUC versus DORA dose, from 0 to 30 mg/Kg, were linear (R2 = 0.18, P = 0.04). The ICP responses during the peak response period (4-16 minutes) versus DORA dose were also linear (R2 = 0.24, P = 0.014). Pretreatment with DORA significantly decreased AUC for the TLPD following stimulation of the DMH/PeF (10 mg/kg, P = 0.045 and 30 mg/kg, P = 0.015). Conclusions: DORAs have the potential to attenuate asynchronous changes in IOP and in ICP and to lessen the extent of TLPDs that may result from central nervous system (CNS) activation.
Elevated tph2 mRNA expression in a rat model of chronic anxiety
(Wiley, 2012-04) Donner, Nina C.; Johnson, Philip L.; Fitz, Stephanie D.; Kellen, Karen E.; Shekhar, Anantha; Lowry, Christopher A.; Psychiatry, School of Medicine
BACKGROUND: Allelic variations in TPH2, the gene encoding tryptophan hydroxylase 2, the rate-limiting enzyme for brain serotonin (5-HT) biosynthesis, may be genetic predictors of panic disorder and panic responses to panicogenic challenges in healthy volunteers. To test the hypothesis that tph2 mRNA is altered in chronic anxiety states, we measured tph2 expression in an established rat model of panic disorder. METHODS: We implanted 16 adult, male rats with bilateral guide cannulae and then primed them with daily injections of the corticotropin-releasing factor (CRF) receptor agonist, urocortin 1 (UCN1, 6 fmoles/100 nl per side, n = 8) or vehicle (n = 8) into the basolateral amygdaloid complex (BL) for 5 consecutive days. Anxiety-like behavior was assessed, 24 hr prior to and 48 hr following priming, in the social interaction (SI) test. A third group (n = 7) served as undisturbed home cage controls. All rats were killed 3 days after the last intra-BL injection to analyze tph2 and slc6a4 (gene encoding the serotonin transporter, SERT) mRNA expression in the dorsal raphe nucleus (DR), the main source of serotonergic projections to anxiety-related brain regions, using in situ hybridization histochemistry. RESULTS: UCN1 priming increased anxiety-related behavior in the SI test compared to vehicle-injected controls and elevated tph2, but not slc6a4, mRNA expression in DR subregions, including the ventrolateral DR/ventrolateral periaqueductal gray (DRVL/VLPAG), a subregion previously implicated in control of panic-related physiologic responses. Tph2 mRNA expression in the DRVL/VLPAG was correlated with increased anxiety-related behavior. CONCLUSION: Our data support the hypothesis that chronic anxiety states are associated with dysregulated tph2 expression.
Eludicating triggers and neurochemical circuits underlying hot flashes in an ovariectomy model of menopause
(2016-02-26) Federici, Lauren Michele; Shekhar, Anantha; Goodlett, Charles; Johnson, Philip L.; Oxford, Gerry S.; Rusyniak, Daniel E.
Menopausal symptoms, primarily hot flashes, are a pressing clinical problem for both naturally menopausal women and breast and ovarian cancer patients, with a high societal and personal cost. Hot flashes are poorly understood, and animal modeling has been scarce, which has substantially hindered the development of non-hormonal treatments. An emerging factor in the hot flash experience is the role of anxiety and stress-related stimuli, which have repeatedly been shown to influence the bother, frequency, and severity of hot flashes. Causal relationships are difficult to determine in a clinical setting, and the use of animal models offers the ability to elucidate causality and mechanisms. The first part of this work details the development and validation of novel animal models of hot flashes using clinically relevant triggers (i.e., compounds or stimuli that cause hot flashes in clinical settings), which also increase anxiety symptoms. These studies revealed that these triggers elicited strong (7-9 Â°C) and rapid hot flash-associated increases in tail skin temperature in rats. In a surgical ovariectomy rat model of menopause, which typically exhibit anxiety-like behavior, hot flash provocation revealed an ovariectomy-dependent vulnerability, which was attenuated by estrogen replacement in tested models. An examination of the neural circuitry in response to the most robust flushing compound revealed increased cellular activity in key thermoregulatory and emotionally relevant areas. The orexin neuropeptide system was hyperactive and presented as a novel target; pretreatment with selective and dual orexin receptor antagonists significantly diminished or eliminated, respectively, the response to a hot flash provocation in ovariectomized rats. The insertion/deletion polymorphism of the serotonin transporter has been linked to increased anxiety-associated traits in humans, and subsequent studies prolonged hot flashes in SERT+/- rats, which also caused hot flashes in highly symptomatic women. These studies indicate the orexin system may be a novel non-hormonal treatment target, and future studies will determine the therapeutic importance of orexin receptor antagonists for menopausal symptoms.

Browsing by Author "Johnson, Philip L."

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