Biology subjects

Murphy, A. Z.

Publications and source records attributed to Murphy, A. Z..

9 recordsLinked to original sources

bioRxiv2025

Learning and Memory Performance in a Rat Model of Perigestational Opioid Exposure

Rationale: Nearly one third of women of reproductive age in the United States are prescribed opioids annually; 14% will fill an opioid prescription during pregnancy, and one in five report misuse. Opioid use during pregnancy has given rise to an increasing population of infants born with gestational opioid exposure. At school age, these children show neurodevelopmental impairment and higher rates of learning disability. Objectives: To characterize how exposure to exogenous opioids during brain development affects learning and memory performance, our lab has developed a rat model of perigestational opioid exposure that closely recapitulates a clinically relevant dosing timeline by beginning morphine exposure before pregnancy and continuing through the first postnatal week. Male and female offspring generated from this model were assessed on several facets of learning and memory during adolescence. Results: Here, we report that morphine exposure selectively impaired spatial learning, as measured by the Barnes Maze, and associative learning, as measured by an Attentional Set Shift Task, without significantly impacting working or short-term memory. Environmental enrichment rescued the spatial learning deficit in males but not females. Conclusion: Our findings suggest that gestational opioid exposure can impair performance in complex cognitive tasks that are attenuated by non-invasive, non-pharmacological intervention.

animal behavior and cognition↗

bioRxiv2024

Disrupted Maternal Behavior in Morphine-Dependent Pregnant Rats and Anhedonia in their Offspring

It is currently estimated that every 15 minutes an infant is born with opioid use disorder and undergoes intense early life trauma due to opioid withdrawal. Clinical research on the long-term consequences of gestational opioid exposure reports increased rates of social, conduct, and emotional disorders in these children. Here, we investigate the impact of perinatal opioid exposure (POE) on behaviors associated with anhedonia and stress in male and female Sprague Dawley rats. Young adult female rats were administered morphine via programmable, subcutaneous micro-infusion pumps before, during, and through one week post gestation. Maternal behavior was examined for fragmentation and entropy for the first two postnatal weeks; offspring were assessed for sucrose preference, social behavior, and stress responsivity. Overall, dams that received morphine across gestation displayed significantly less pup-directed behavior with increased fragmentation for nursing and higher entropy scores. In adolescence, male and female rat offspring exposed to morphine displayed reduced sucrose preference and, as adults, spent significantly less time socially interacting with familiar conspecifics. Changes in social behaviors were linked to increased activity in nondopaminergic mesolimbic reward brain regions. Although no treatment effects were observed in forced swim test performance, corticosterone levels were significantly increased in POE adult males. Together, these results suggest that perinatal morphine exposure results in anhedonic behavior, possibly due to fragmented and unpredictable maternal behavior in opioid-dependent dams. Significance StatementClinical and preclinical research has shown that early life stress can produce lifelong depression-like symptoms. Here, we show that maternal opioid use during pregnancy produces depression-like symptoms in the offspring. We also observed disrupted maternal behavior in morphine-exposed dams that is similar to the changes in maternal behavior reported following other forms of early life stress. We propose that the stress of opioid exposure and suboptimal rearing leads to reduced sucrose preference, increased stress reactivity, and social avoidance behavior in the offspring, all of which are characteristics of anhedonia.

neuroscience↗

bioRxiv2023

Early life pain alters the response to an immune challenge in adult male and female rats

Infants born prematurely are more likely to be admitted to the Neonatal Intensive Care Unit (NICU) where they experience upwards of 10-18 painful procedures each day, often with no anesthesia or analgesia. Pre-clinical studies have shown that early exposure to pain disrupts CNS development in multiple ways that persist into adulthood, with similar findings observed clinically. The present study explores the effects of neonatal injury on the response to an immune challenge in adulthood. Male and female rats were exposed to a short-term inflammatory insult induced by intraplantar administration of 1% carrageenan (CGN) on the day of birth (P0). In adulthood (P60-P90), rats were implanted with Thermicron iButtons to monitor core body temperature; 14 days later, lipopolysaccharide (LPS) was administered to elicit an immune response. Rats were sacrificed after 24 hours or at their peak fever point and brain tissue collected for immunohistochemical analysis. LPS administration resulted in a significantly greater febrile response in males and females exposed to early life pain compared to controls. Immunohistological analysis revealed sex and treatment differences in Fos labeling in several brain regions, including the PVN. No sex or treatment differences were observed for VGat, VGlut2, or EP3R expression in the MnPO; however, all three increased significantly following LPS administration. Together, these studies are consistent with clinical studies reporting children experiencing unresolved pain during the perinatal period show an increased severity of sickness behavior and altered immune signaling following exposure to a pathogen and will provide a foundation for future studies examining the biological underpinnings.

neuroscience↗

bioRxiv2023

Perigestational Opioid Exposure Alters Alcohol-Driven Reward Behaviors in Adolescent Rats

Every fifteen minutes, a baby is born in the U.S. experiencing neonatal opioid withdrawal syndrome (NOWS). Since 2004, the rate of NOWS has increased 7-fold. Clinical studies have established intrauterine exposure to drugs of abuse as a risk factor for adverse health outcomes in adult life, including the propensity for future illicit drug use. Despite extensive knowledge about common mechanisms of action in the neural circuitry that drives opioid and alcohol reward, there is little data on the risks that those born with NOWS face regarding alcohol use later in life. Here, we investigate the impact of perigestational opioid exposure (POE) on the mesolimbic reward system of male and female Sprague Dawley rats at postnatal and adolescent ages. Our laboratory has developed a clinically relevant model for morphine exposure spanning pre-conception to the first week of life. Using this model, we found that POE increased alcohol consumption in female rats under noncontingent conditions, and inversely, reduced alcohol consumption in both male and female rats during operant conditioning sessions. Operant responding was also reduced for sucrose, suggesting that the impact of POE on reward-seeking behaviors is not limited to drugs of abuse. Expression of {micro}-opioid receptors was also significantly altered in the nucleus accumbens and medial habenula, regions previously shown to play a significant role in reward/aversion circuitry. Significance StatementEarly life exposure to opioids is known to alter future drug behavior in rats. In the present study, female rats exposed to morphine via their mothers throughout and after pregnancy exhibited increased alcohol consumption when allowed to consume freely. During operant conditioning, however, male and female rats exposed to gestational morphine decreased consumption of alcohol as well as sucrose. We also observed that gestational morphine exposure altered {micro}-opioid receptor expression in reward-related brain regions. Our study provides the first evidence of changes in alcohol-directed reward behavior in a gestational opioid exposure rat model.

neuroscience↗

bioRxiv2023

Increased LPS-Induced Fever and Sickness Behavior in Adult Male and Female Rats Perinatally Exposed to Morphine

As a result of the current opioid crisis, the rate of children born exposed to opioids has skyrocketed. Later in life, these children have an increased risk for hospitalization and infection, raising concerns about potential immunocompromise, as is common with chronic opioid use. Opioids can act directly on immune cells or indirectly via the central nervous system to decrease immune system activity, leading to increased susceptibility, morbidity, and mortality to infection. However, it is currently unknown how perinatal opioid exposure (POE) alters immune function. Using a clinically relevant and translatable model of POE, we have investigated how baseline immune function and the reaction to an immune stimulator, lipopolysaccharide, is influenced by in utero opioid exposure in adult male and female rats. We report here that POE potentiates the febrile and neuroinflammatory response to lipopolysaccharide, likely as a consequence of suppressed immune function at baseline (including reduced antibody production). This suggests that POE increases susceptibility to infection by manipulating immune system development, consistent with the clinical literature. Investigation of the mechanisms whereby POE increases susceptibility to pathogens is critical for the development of potential interventions for immunosuppressed children exposed to opioids in utero. HighlightsO_LIPerinatal exposure to morphine leads to increased fever and sickness post-LPS C_LIO_LIPerinatal exposure to morphine alters peripheral immunity C_LIO_LIPerinatal exposure to morphine increases microglial activation C_LI

neuroscience↗

bioRxiv2023

Perinatal Morphine Exposure Induces Long-Term Changes in the Intestinal Microbiota of Male and Female Rats

The increased use of opioids by women of reproductive age has resulted in a dramatic rise in number of infants exposed to opioids in utero. Although perinatal opioid exposure (POE) has been associated with an elevated risk of infection and hospitalization later in life, the mechanism(s) by which opioids influence immune development and maturation is not fully elucidated. Alterations in the intestinal microbiota composition, which leads to changes in immune training and maturation, could be at play. Chronic opioid use in adults is associated with a proinflammatory and pathogenic microbiota composition; therefore, we hypothesized here that in utero morphine exposure could negatively affect intestinal microbiota composition, leading to alterations in immune system function. We report that a clinically-relevant model of perinatal opioid exposure, in rats, induces profound intestinal microbiota dysbiosis that is maintained into adulthood. Furthermore, microbial maturity was reduced in morphine-exposed offspring. This suggests that increased risk of infection observed in children exposed to opioids during gestation may be a consequence of microbiota alterations with downstream impact on immune system development. Further investigation of how perinatal morphine induces dysbiosis will be critical to the development of early life interventions designed to ameliorate the increased risk of infection observed in these children.

neuroscience↗

bioRxiv2022

Altered PVN-to-CA2 hippocampal oxytocin pathway and reduced number of oxytocin-receptor expressing astrocytes in heart failure rats

Oxytocinergic actions within the hippocampal CA2 are important for neuromodulation, memory processing and social recognition. However, the source of the OTergic innervation, the cellular targets expressing the OT receptors (OTRs) and whether the PVN-to-CA2 OTergic system is altered during heart failure (HF), a condition recently associated with cognitive and mood decline, remains unknown. Using immunohistochemistry along with retrograde monosynaptic tracing, RNAscope and a novel OTR-Cre rat line, we show that the PVN (but not the supraoptic nucleus) is an important source of OTergic innervation to the CA2. These OTergic fibers were found in many instances in close apposition to OTR expressing cells within the CA2. Interestingly, while only a small proportion of neurons were found to express OTRs ([~]15%), this expression was much more abundant in CA2 astrocytes ([~]40%), an even higher proportion that was recently reported for astrocytes in the central amygdala. Using an established ischemic rat heart failure (HF) model, we found that HF resulted in robust changes in the PVN-to-CA2 OTergic system, both at the source and target levels. Within the PVN, we found an increased OT immunoreactivity, along with a diminished OTR expression in PVN neurons. Within the CA2 of HF rats, we observed a blunted OTergic innervation, along with a diminished OTR expression, which appeared to be restricted to CA2 astrocytes. Taken together, our studies highlight astrocytes as key cellular targets mediating OTergic PVN inputs to the CA2 hippocampal region. Moreover, provides the first evidence for an altered PVN-to-CA2 OTergic system in HF rats, which could potentially contribute to previously reported cognitive and mood impairments in this animal model.

neuroscience↗

bioRxiv2022

Age-induced changes in Mu Opioid Receptor signaling in the midbrain Periaqueductal Gray of male and female rats

The analgesic effects of opioids are attenuated in aged rats. Opioids such as morphine have decreased analgesic potency (but not efficacy) in aged rodents compared to adults; however, the neural mechanisms underlying this attenuated response are not yet known. The present study investigated the impact of advanced age and biological sex on opioid signaling in the ventrolateral periaqueductal gray (vlPAG) in the presence of chronic inflammatory pain. Assays measuring mu-opioid receptor (MOR) radioligand binding, GTP{gamma}S binding, receptor phosphorylation, cAMP inhibition, and regulator of G-protein signaling (RGS) protein expression were performed on vlPAG tissue from adult (2-3mos) and aged (16-18mos) male and female rats. Persistent inflammatory pain was induced by intraplantar injection of Complete Freunds Adjuvant (CFA). Adult males exhibited the highest MOR binding potential and the highest G-protein activation (activation efficiency ratio) in comparison to aged males and females (adult and aged). No impact of advanced age or sex on MOR phosphorylation state was observed. DAMGO-induced cAMP inhibition was highest in the vlPAG of adult males compared to aged males and females (adult and aged). vlPAG levels of RGS4 and RGS9-2, critical for terminating G-protein signaling, were assessed using RNAscope. Adult rats (both males and females) exhibited lower levels of vlPAG RGS4 and RGS9-2 mRNA expression compared to aged males and females. The observed age-related reductions in vlPAG MOR binding potential, G-protein activation efficiency, and cAMP inhibition, along with the observed age-related increases in RGS4 and RGS9-2 vlPAG expression, provide potential mechanisms whereby the potency of opioids is decreased in the aged population. These results have significant implications for pain management in this population. HighlightsO_LIAged males and females (adult and aged) exhibit reduced vlPAG -opioid receptor binding potential compared to adult males. C_LIO_LIAged males and females (adult and aged) exhibit reduced opioid-induced vlPAG G-protein activation compared to adult males. C_LIO_LIAged males and females (adult and aged) exhibit reduced vlPAG MOR mediated cAMP inhibition compared to adult males. C_LIO_LIAged rats (males and females) exhibit increased vlPAG mRNA expression of Regulator of G-Protein Signaling (RGS) proteins RGS4 and RGS9-2 compared to adult rats (males and females), which may explain the reduced receptor signaling observed in aged animals. C_LIO_LIThese coordinate decreases in opioid receptor signaling may explain the previously reported reduced potency of opioids to produce pain relief in females and aged rats. C_LI

neuroscience↗

bioRxiv2020

Advanced age attenuates the antihyperalgesic effect of morphine and decreases μ-opioid receptor expression and binding in the rat midbrain Periaqueductal Gray in male and female rats

The present study investigated the impact of advanced age on morphine modulation of persistent inflammatory pain in male and female rats. The impact of age, sex, and pain on -opioid receptor (MOR) expression and binding in the ventrolateral PAG (vlPAG) was also examined using immunohistochemistry and receptor autoradiography. Intraplantar administration of Complete Freunds adjuvant induced comparable levels of edema and hyperalgesia in adult (2-3mos) and aged (16-18mos) male and female rats. Morphine potency was highest in adult males, with a two-fold decrease in morphine EC50 observed in aged versus adult males (10.22mg/kg versus 5.19mg/kg). Adult and aged female rats also exhibited significantly higher EC50 values (10.69 mg/kg and 9.00 mg/kg, respectively) compared to adult males. The upward shift in EC50 from adult to aged males was paralleled by a reduction in vlPAG MOR expression and binding. The observed age-related reductions in morphine potency and vlPAG MOR expression and binding have significant implications in pain management in the aged population.

neuroscience↗