Effects of L-Dopa, SKF-38393, and Quinpirole on exploratory, anxiety- and depressive-like behaviors in pubertal female and male mice

Adolescence is a phase of substantial changes in the brain, characterized by maturational remodeling of many systems. This remodeling allows functional plasticity to adapt in a changing environment but turns this period into a neurodevelopmental vulnerable window. The dopaminergic system is under morphological and physiological changes during this phase. The disruption of its balance can lead to molecular variation and abnormal behavior - representing a risk factor for neuropsychiatric disorders. In the present study, we investigated if changes in the dopaminergic tone alter mice behavior in a receptor and sex-specific manner, specifically in the beginning of puberty period. We administered L-Dopa, SKF-38393 (D1 dopamine receptor agonist) and Quinpirole (D2 dopamine receptor agonist) and tested male and female mice motor, anxiety- and depressive-like behavior. While females displayed an impaired exploratory drive, males presented an intense depressive-like response. Our results provide insights into the function of dopaminergic development in adolescent behavior and highlight the importance of studies in this time window with male and female subjects.

Effects of D1 agonist on working memory and cognitive flexibility in a zebrafish model of aging

Part of the natural aging process is a decline in memory and executive function, even in the absence of disease. The dopaminergic system has been implicated in age associated alterations in cognitive flexibility and working memory. Here we examine the relationship between cognitive performance and dopamine function of young-adult and aging zebrafish (Danio rerio). We reveal an age-related decrease in working memory and cognitive flexibility when faced with a negative feedback loop for informing search strategies in the Free-Movement Pattern (FMP) Y-maze. We additionally found a selective role for dopamine D1-like receptor activation, by treatment with partial D1/D5 receptor agonist SKF-38393, for enhancing working memory performance in aged zebrafish, but not for restoring behavioural flexibility. We additionally noted that baseline performance levels were critical to the effect of SKF-38393 on cognitive flexibility. This reduction in behavioural plasticity was accompanied by a down-regulation of the dopamine transporter (dat) and a decrease in metabolic activity. Together, these findings suggest a selective role for cognitive enhancement via dopamine D1 receptors; however, beneficial effects are dependent on behavioural task and baseline performance, emphasising the need for caution when treating cognitive deficits with dopamine agonists to improve cognitive impairment of some tasks. This study further supports the use of zebrafish as a model of aging and cognitive decline.

PO-131 Impact of short-term inhibition of PKA in Nucleus Accumbens on voluntary wheel running

Objective Based upon a Booth lab goal of establishing molecular regulators of physical activity motivation, my current study focuses on the effects of short-term inhibition of protein kinase A (PKA) activity in the nucleus accumbens (NAc). The NAc is a brain region integral to motivated behaviors. Downstream immediate-early gene (IEG) expression from PKA has been shown to exhibit rapid responses to acute stimuli, such as voluntary wheel-running behavior. According to previous work in our lab, long-term NAc overexpression of the endogenous PKA inhibitor, Protein Kinase Inhibitor Alpha (PKIα), increased nightly running distance in rats selectively bred for low voluntary running (LVR) behavior (Mol Neurobiol 2018 Jun 21). However, paradoxically, the same PKIα overexpression failed to increase running distance in wild-type (WT) rats. It is known that chronic manipulation of the NAc PKA pathway produces different molecular (gene expression profiles) and behavioral outcomes from that of acute manipulations. Given the above, the goal of the current work is to determine how short-term inhibition of PKA in the NAc influences its downstream gene networks and the nightly voluntary running behavior in WT rats. Methods An ex vivo preparation of the NAc was utilized to determine the effects of Rp-cAMPS, a selective protein kinase A inhibitor, upon its stimulation of dopamine D1-like receptor agonist SKF 38393 on downstream gene expression level in sedentary WT female rats. Further, real-time PCR was implemented to analyze the transcriptional expression of IEGs (Homer-1, Arc, Zif268) following Rp-cAMPS administration. Results Data showed that there were no significant difference of mRNA level for Homer-1, Arc or Zif268 among the vehicle, 50uM, 100uM and 200uM Rp-cAMPS treatment groups upon the stimulation of 10uM SKF 38393. Conclusions In addition to the PKA, other protein kinases such as Ca++ activated and growth factor activated kinases have both been shown to phosphorylate CREB at Ser133, and thus, lead to activation of gene transcription. Given the above results of the ex vivo experiment, in which NAc slices were treated with multiple dosages of Rp-cAMPS concurrent with the stimulation of SKF 38393, it is possible that other protein kinase pathways could be compensating the effects of short-term inhibition of PKA and, in turn, lead to no difference of IEG expression. Further experiments will need to be performed in order to testify this hypothesis.

Modulation of spinal motor networks by astrocyte-derived adenosine is dependent on D1-like dopamine receptor signaling

Astrocytes modulate many neuronal networks, including spinal networks responsible for the generation of locomotor behavior. Astrocytic modulation of spinal motor circuits involves release of ATP from astrocytes, hydrolysis of ATP to adenosine, and subsequent activation of neuronal A1 adenosine receptors (A1Rs). The net effect of this pathway is a reduction in the frequency of locomotor-related activity. Recently, it was proposed that A1Rs modulate burst frequency by blocking the D1-like dopamine receptor (D1LR) signaling pathway; however, adenosine also modulates ventral horn circuits by dopamine-independent pathways. Here, we demonstrate that adenosine produced upon astrocytic stimulation modulates locomotor-related activity by counteracting the excitatory effects of D1LR signaling and does not act by previously described dopamine-independent pathways. In spinal cord preparations from postnatal mice, a D1LR agonist, SKF 38393, increased the frequency of locomotor-related bursting induced by 5-hydroxytryptamine and N-methyl-d-aspartate. Bath-applied adenosine reduced burst frequency only in the presence of SKF 38393, as did adenosine produced after activation of protease-activated receptor-1 to stimulate astrocytes. Furthermore, the A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine enhanced burst frequency only in the presence of SKF 38393, indicating that endogenous adenosine produced by astrocytes during network activity also acts by modulating D1LR signaling. Finally, modulation of bursting by adenosine released upon stimulation of astrocytes was blocked by protein kinase inhibitor-(14–22) amide, a protein kinase A (PKA) inhibitor, consistent with A1R-mediated antagonism of the D1LR/adenylyl cyclase/PKA pathway. Together, these findings support a novel, astrocytic mechanism of metamodulation within the mammalian spinal cord, highlighting the complexity of the molecular interactions that specify motor output. NEW & NOTEWORTHY Astrocytes within the spinal cord produce adenosine during ongoing locomotor-related activity or when experimentally stimulated. Here, we show that adenosine derived from astrocytes acts at A1 receptors to inhibit a pathway by which D1-like receptors enhance the frequency of locomotor-related bursting. These data support a novel form of metamodulation within the mammalian spinal cord, enhancing our understanding of neuron-astrocyte interactions and their importance in shaping network activity.

Разнонаправленные эффекты стимуляции и блокады D1-типа дофаминовых рецепторов у пренатально стрессированных самцов крыс при дефиците андрогенов в тесте Порсолта

Исследовали эффекты хронического введения агониста D1-типа дофаминовых рецепторов — SKF-38393 (0,1 мг/кг внутрибрюшинно) и антагониста D1-типа дофаминовых рецепторов — SCH-23390 (0,1 мг/кг внутрибрюшинно) изолированно или в комбинации с низкой дозой тестостерона пропионата (0,5 мг/кг подкожно) на депрессивноподобное поведение половозрелых (3 мес) самцов крыс в условиях дефицита андрогенов в организме, которые родились от самок крыс, подвергнутых пренатальному стрессорному воздействию в последнюю треть беременности. Дофаминергические вещества и тестостерона пропионат вводили в течение 14 дней ежедневно 1 раз в сутки пренатально стрессированным самцам крыс через 2 недели после гонадэктомии. В тесте Порсолта у пренатально стрессированных гонадэктомированных (ГЭ) и ГЭ самцов крыс, получавших изолированно или комбинированно фармакологические вещества, регистрировали следующие показатели: время неподвижности, время активного и пассивного плавания. Установлено, что введение SKF-38393 оказывало антидепрессивное действие, тогда как введение SCH-23390 не влияло на характер депрессивноподобного поведения у пренатально стрессированных ГЭ крыс. Комбинированное введение SKF-38393 с тестостерона пропионатом приводило к еще большому снижению выраженности депрессивноподобного поведения, тогда как хроническое введение SCH-23390 в сочетании с тестостерона пропионатом, напротив, проявляло продепрессивное действие у пренатально стрессированных ГЭ самцов.

Влияние агонистов D1- и D2-типов дофаминовых рецепторов на тревожное поведение и уровень половых гормонов у гонадэктомированных самцов

Изучено влияние хронического введения SKF-38393 (0,1 мг/кг внутрибрюшинно) и квинпирола (0,1 мг/кг внутрибрюшинно), а также комбинации этих веществ с тестостерона пропионатом в низкой дозе (0,5 мг/кг подкожно) в течение 14 дней на тревожное поведение у интактных и гонадэктомированных (ГЭ) крыс в тесте приподнятый «крестообразный» лабиринт. Результаты настоящего исследования свидетельствуют о том, что хроническое введение квинпирола оказывает анксиолитическое действие и корректирует уровень половых гормонов у ГЭ самцов.

Selective modulation of GABAergic tonic current by dopamine in the nucleus accumbens of alcohol-dependent rats

The nucleus accumbens (NAcc) is a key structure of the mesolimbic dopaminergic reward system and plays an important role in mediating alcohol-seeking behaviors. Alterations in glutamatergic and GABAergic signaling were recently demonstrated in the NAcc of rats after chronic intermittent ethanol (CIE) treatment, a model of alcohol dependence. Here we studied dopamine (DA) modulation of GABAergic signaling and how this modulation might be altered by CIE treatment. We show that the tonic current ( Itonic) mediated by extrasynaptic γ-aminobutyric acid type A receptors (GABAARs) of medium spiny neurons (MSNs) in the NAcc core is differentially modulated by DA at concentrations in the range of those measured in vivo (0.01–1 μM), without affecting the postsynaptic kinetics of miniature inhibitory postsynaptic currents (mIPSCs). Use of selective D1 receptor (D1R) and D2 receptor (D2R) ligands revealed that Itonic potentiation by DA (10 nM) is mediated by D1Rs while Itonic depression by DA (0.03–1 μM) is mediated by D2Rs in the same MSNs. Addition of guanosine 5′- O-(2-thiodiphosphate) (GDPβS) to the recording pipettes eliminated Itonic decrease by the selective D2R agonist quinpirole (5 nM), leaving intact the quinpirole effect on mIPSC frequency. Recordings from CIE and vehicle control (CIV) MSNs during application of D1R agonist (SKF 38393, 100 nM) or D2R agonist (quinpirole, 2 nM) revealed that SKF 38393 potentiated Itonic to the same extent, while quinpirole reduced Itonic to a similar extent, in both groups of rats. Our data suggest that the selective modulatory effects of DA on Itonic are unaltered by CIE treatment and withdrawal.