Amanda M. Maple

Ontogenetic quinpirole treatment produces long-lasting decreases in the expression of Rgs9, but increases Rgs17 in the striatum, nucleus accumbens and frontal cortex

Ontogenetic treatment of rats with the dopamine D2‐like receptor agonist quinpirole produces a significant increase in dopamine D2 receptor sensitivity that persists throughout the animals lifetime, a phenomenon known as D2 priming. The present study was designed to investigate the effects of priming of the D2 receptor on the expression of three different members of the regulator of G‐protein signaling (RGS) family: Rgs4, Rgs9 and Rgs17. Male offspring were ontogenetically treated with quinpirole or saline from postnatal days (P)1–21 and raised to adulthood. On ∼ P65, animals were given an acute quinipirole injection (0.1 mg/kg) and the number of yawns was recorded for 1 h after the injection. Yawning has been shown to be a behavioural event mediated by the dopamine D2/D3 receptor. Animals ontogenetically treated with quinpirole demonstrated a significant 2.5‐fold increase in yawning as compared to controls. Rgs transcripts were analysed through in situ hybridization several weeks later. Rats ontogenetically treated with quinpirole demonstrated a significant decrease in Rgs9 expression in the frontal cortex, but a more robust decrease in the striatum and nucleus accumbens as compared to controls. Regarding Rgs17, ontogenetic quinpirole produced a modest but significant increase in expression in the same brain areas. There were no significant differences in Rgs4 expression produced by drug treatment in any of the brain regions analysed. This study demonstrates that ontogenetic quinpirole treatment, which results in priming of the D2 receptor, results in significant decreases in Rgs9, which has been shown to regulate G‐protein coupling to D2 receptors.

Schizophrenia and Substance Abuse Comorbidity: Nicotine Addiction and the Neonatal Quinpirole Model

This review focuses on nicotine comorbidity in schizophrenia, and the insight into this problem provided by rodent models of schizophrenia. A particular focus is on age differences in the response to nicotine, and how this relates to the development of the disease and difficulties in treatment. Schizophrenia is a particularly difficult disease to model in rodents due to the fact that it has a plethora of symptoms ranging from paranoia and delusions of grandeur to anhedonia and negative affect. The basis of these symptoms is believed to be due to neurochemical abnormalities and neuropathology in the brain, which most models have attempted to emulate. A brief review of findings regarding nicotine use and abuse in schizophrenics is presented, with findings using rodent models that have been able to provide insight into the mechanisms of addiction. A common clinical approach to the treatment of nicotine addiction in the schizophrenic population has been that these drugs are used for self-medication purposes, and it is clear that self-medication may actually be directed at several symptoms, including cognitive impairment and anhedonia. Finally, our laboratory has reported across a series of studies that neonatal treatment with the dopamine D2/D3 receptor agonist quinpirole results in long-term increases in dopamine-like receptor sensitivity, consistent with data reporting increases in dopamine D2 receptor function in schizophrenia. Across these studies, we have reported several behavioral, neurochemical, and genetic consistencies with the disease, and present a hypothesis for what we believe to be the basis of psychostimulant addiction in schizophrenia.

Htr2a Expression Responds Rapidly to Environmental Stimuli in an Egr3-Dependent Manner

Pharmacologic and genetic findings have implicated the serotonin 2A receptor (5-HT2AR) in the etiology of schizophrenia. Recent studies have shown reduced 5-HT2AR levels in schizophrenia patients, yet the cause of this difference is unknown. Environmental factors, such as stress, also influence schizophrenia risk, yet little is known about how environment may affect this receptor. To determine if acute stress alters 5-HT2AR expression, we examined the effect of sleep deprivation on cortical Htr2a mRNA in mice. We found that 6 h of sleep deprivation induces a twofold increase in Htr2a mRNA, a more rapid effect than has been previously reported. This effect requires the immediate early gene early growth response 3 (Egr3), as sleep deprivation failed to induce Htr2a expression in Egr3-/- mice. These findings provide a functional link between two schizophrenia candidate genes and an explanation of how environment may influence a genetic predisposition for schizophrenia.

Adulthood olanzapine treatment fails to alleviate decreases of ChAT and BDNF RNA expression in rats quinpirole-primed as neonates.

Neonatal quinpirole (dopamine D(2)/D(3) agonist) treatment to rats has been shown to increase dopamine D(2) receptor sensitivity throughout the animals lifetime. Male and female Sprague-Dawley rats were neonatalally treated with quinpirole (1 mg/kg) from postnatal days (P) 1-21 and raised to adulthood. Beginning on P62, rats were administered the atypical antipsychotic olanzapine (2.5 mg/kg) twice daily for 28 days. Starting 1 day after the end of olanzapine treatment, animals were behaviorally tested on the place and match-to-place version of the Morris water maze (MWM) over seven consecutive days, and a yawning behavioral test was also performed to test for sensitivity of the D(2) receptor 1 day following MWM testing. Similar to results from a past study, olanzapine alleviated cognitive impairment on the MWM place version and increases in yawning produced by neonatal quinpirole treatment. Brain tissue analyses showed that neonatal quinpirole treatment resulted in a significant decrease of hipppocampal ChAT and BDNF RNA expression that were unaffected by adulthood olanzapine treatment, although adulthood olanzapine treatment produced a significant increase in cerebellar ChAT RNA expression. There were no significant effects of drug treatment on NGF RNA expression in any brain area. These results show that neonatal quinpirole treatment produced significant decreases of protein RNA expression that is specific to the hippocampus. Although olanzapine alleviated cognitive deficits produced by neonatal quinpirole treatment, it did not affect expression of proteins known to be important in cognitive performance.

Neonatal quinpirole treatment produces prepulse inhibition deficits in adult male and female rats.

We have shown that repeated neonatal quinpirole (QUIN; a dopamine D2-like receptor agonist) treatment in rats produces long-lasting supersensitization of dopamine D2 receptors that persists into adulthood but without producing a change in receptor number. The current study was designed to analyze the effects of neonatal QUIN on auditory sensorimotor gating as measured through prepulse inhibition (PPI). Male and female Sprague-Dawley rats were neonatally treated with QUIN (1mg/kg) or saline from postnatal days (P)1-21. At P60, the number of yawns was recorded for a 1h period in response to an acute QUIN (1mg/kg) injection as yawning is a D2-like receptor mediated behavioral event. Five days later, rats began (PPI) behavioral testing in two phases. In phase I, three different prepulse intensities (73, 76, and 82dB) were administered 100-ms before a 115dB pulse on 10 consecutive days. In phase II, three different interstimulus intervals (ISI; 50, 100, and 150ms) were inserted between the 73 or 76dB prepulse and 115dB pulse over 10 consecutive days of testing. A PPI probe trial was administered at the end of each phase after an acute 100μg/kgi.p. injection of QUIN to all animals. Replicating previous work, neonatal QUIN enhanced yawning compared to controls, verifying D2 receptor supersensitization. Regarding PPI, neonatal QUIN resulted in deficits across both phases of testing persistent across all testing days. Probe trial results revealed that acute QUIN treatment resulted in more robust PPI deficits in neonatal QUIN animals, although this deficit was related to prepulse intensity and ISI. These findings provide evidence that neonatal QUIN treatment results in deficits of auditory sensorimotor gating in adulthood as measured through PPI.

Attenuated Late-Phase Arc Transcription in the Dentate Gyrus of Mice Lacking Egr3

The dentate gyrus (DG) engages in sustained Arc transcription for at least 8 hours following behavioral induction, and this time course may be functionally coupled to the unique role of the DG in hippocampus-dependent learning and memory. The factors that regulate long-term DG Arc expression, however, remain poorly understood. Animals lacking Egr3 show less Arc expression following convulsive stimulation, but the effect of Egr3 ablation on behaviorally induced Arc remains unknown. To address this, Egr3−/− and wild-type (WT) mice explored novel spatial environments and were sacrificed either immediately or after 5, 60, 240, or 480 minutes, and Arc expression was quantified by fluorescence in situ hybridization. Although short-term (i.e., within 60 min) Arc expression was equivalent across genotypes, DG Arc expression was selectively reduced at 240 and 480 minutes in mice lacking Egr3. These data demonstrate the involvement of Egr3 in regulating the late protein-dependent phase of Arc expression in the DG.

Effects of Repeated Ropinirole Treatment on Phencyclidine-Induced Hyperlocomotion, Prepulse Inhibition Deficits, and Social Avoidance in Rats

Phencyclidine (PCP), a noncompetitive N-methyl d-aspartate (NMDA) receptor antagonist, provides the most complete pharmacologic model of schizophrenia in humans and animals. Acute PCP causes hyperlocomotion, disrupts prepulse inhibition (PPI), and increases social avoidance in rats. We have previously shown that repeated treatment with the dopamine (DA) D2-like receptor agonists, quinpirole or ropinirole, prevents agonist-induced PPI disruption. In the present study, we examined whether repeated ropinirole treatment similarly attenuates the effects of PCP in a more complete model of schizophrenia symptoms and examined the effect of repeated D2-like agonist treatment on locomotion, PPI, and social interaction after acute PCP challenge. The acute effect of PCP (3.0 or 6.0 mg/kg) on locomotor activity was examined to establish a minimum effective dose. Thereafter, the effect of PCP challenge (3.0 mg/kg) on locomotor activity, PPI, and social interaction was assessed in adult male rats before or 7–10 days after termination of repeated daily treatment with ropinirole (0.1 mg/kg) or saline vehicle (0.1 ml/kg) for 28 days. Repeated ropinirole treatment attenuates PCP-induced hyperlocomotion, PPI deficits, and social avoidance. These findings suggest that repeated ropinirole treatment might affect a final common pathway that is vulnerable to both PCP- and dopamine agonist–induced behavioral disruption, thereby providing an alternative approach to block the effects of PCP.

Activity-regulated cytoskeleton-associated protein predicts response to cognitive remediation among individuals with first-episode psychosis

Fig. 1a. Putative biological pathway for memory and response to cognitive remediation. Numerous proteins associated with risk for psychotic disorders (outlined in red) regulate expression of ARC. As IEGs, both EGR3 and ARC are activated in response to environmental stimuli (red hatched arrows) such as those that trigger learning. This may be via NMDARs or other pathway genes. Maintenance of ARC expression requires EGR3. Dysfunction in ARC, or its upstream regulators may disrupt the normal neurobiological response to stress, setting the stage for symptoms of schizophrenia. Abbreviations: NMDAR N-methyl d-aspartate receptor; NRG2, Neuregulin 1; ERBB4, ErbB4 receptor; NFAT, nuclear factor of activated T cells; EGR3, Early growth response 3; ARC, Activity-regulated cytoskeleton-associated protein. Growing evidence suggests that cognitive remediation (CR) defined by the Cognitive Remediation Experts Workshop as “a behavioral training based intervention that aims to improve cognitive processes with the goal of durability and generalization” -may ameliorate the cognitive deficits that accompany psychotic disorders. However, as a therapy, it is costly and requires specially trained clinicians with expertise and instrumentation. Therefore, the ability to pre-identify individuals who would most likely benefit from this intervention would decrease the time and cost of treatment. Consequently, several studies have investigated possible genetic predictors of response to CR. Focusing primarily on the dopaminergic modulator catechol-O-methyltransferase (COMT), results from these studies are equivocal andmay be confounded by the effects of antipsychotic medication (Bosia et al., 2014). We hypothesized that genes involved in memory and synaptic plasticity may influence the response to CR as these processes are likely stimulated by, and critical for, this therapy. Our prior work has defined an activity-dependent pathway of neuronal proteins that may influence the cognitive symptoms of psychotic illnesses (Huentelman et al., 2015). The proteins in this pathway, beginning with N-methyl D-aspartate receptors and culminating in expression of the immediate early gene activity-regulated cytoskeleton-associated protein (ARC), are essential for memory formation and synaptic plasticity (see Fig. 1a). For the current study, we focused on the role of ARC in moderating response to CR given (i) its association with schizophrenia susceptibility (Huentelman et al., 2015) and (ii) evidence supporting a putative role of ARC in translating environmental learning events (e.g., CR exercises) into changes in neural circuitry (Shepherd and Bear, 2011). This project was approved by the University of Arizona Institutional Review Board. All participants provided informed consent prior to completing study procedures. This study was completed in accordance with the Declaration of Helsinki. Seventy-two individuals with first-episode psychosis were recruited from the Early Psychosis Intervention Center (EPICENTER: Breitborde et al., 2015). Eligibility criteria included: diagnosis of a schizophreniaspectrum disorder or affective disorder with psychotic features, less than 5 years since first onset of psychotic symptoms, being between the ages of 15–35, and no evidence of premorbid intellectual disability. Among our participants, there were 19 women and 53 men, with an average age of 22.72 years and a median duration of psychotic illness of 12.34 months. Participants completed a six-month trial of metacognitive remediation therapy (MCR: Breitborde et al., 2016)—an intervention combining computerized CR exercises and therapist lead metacognitive skills development activities. Cognitive functioning was assessed before and after MCR using the overall cognitive composite score of the MATRICS Consensus Cognitive Battery (MCCB: Nuechterlein et al., 2008).

Neuronal reorganization in adult rats neonatally exposed to (±)-3,4-methylenedioxymethamphetamine

The abuse of methylenedioxymethamphetamine (MDMA) during pregnancy is of concern. MDMA treatment of rats during a period of brain growth analogous to late human gestation leads to neurochemical and behavioral changes. MDMA from postnatal day (P)11–20 in rats produces reductions in serotonin and deficits in spatial and route-based navigation. In this experiment we examined the impact of MDMA from P11 to P20 (20 mg/kg twice daily, 8 h apart) on neuronal architecture. Golgi impregnated sections showed significant changes. In the nucleus accumbens, the dendrites were shorter with fewer spines, whereas in the dentate gyrus the dendritic length was decreased but with more spines, and for the entorhinal cortex, reductions in basilar and apical dendritic lengths in MDMA animals compared with saline animals were seen. The data show that neuronal cytoarchitectural changes are long-lasting following developmental MDMA exposure and are in regions consistent with the learning and memory deficits observed in such animals.