Constitutive Ret signaling leads to long-lasting expression of amphetamine-induced place conditioning via elevation of mesolimbic dopamine

Addictive drugs enhance dopamine release in the striatum, which can lead to compulsive drug-seeking after repeated exposure. Glial cell line-derived neurotrophic factor (GDNF) is an important regulator of midbrain dopamine neurons, and may play a mechanistic role in addiction-related behaviors. To elucidate the components of GDNF-signaling that contribute to addiction-related behaviors of place preference and its extinction, we utilized two genetically modified GDNF mouse models in an amphetamine induced conditioned place preference (CPP) paradigm and evaluated how the behavioral findings correlate with dopamine signaling in the dorsal and ventral striatum. We utilized two knock-in mouse strains to delineate contributions of GDNF and Ret signaling using MEN2B mice (constitutively active GDNF receptor Ret), and GDNF hypermorphic mice (enhanced endogenous GDNF expression). The duration of amphetamine-induced CPP was greatly enhanced in MEN2B mice, but not in the GDNF hypermorphic mice. The enhanced duration of CPP was correlated with increased tyrosine hydroxylase (TH) expression and dopamine content in the ventral striatum. Together, our results suggest that downstream components of GDNF signaling, in this case Ret, may mediate persistent drug-seeking behavior through increased TH expression and dopamine levels in the mesolimbic dopamine neurons. (C) 2017 Elsevier Ltd. All rights reserved.Peer reviewe

Prolyl Oligopeptidase Regulates Dopamine Transporter Phosphorylation in the Nigrostriatal Pathway of Mouse

Alpha-synuclein is the main component of Lewy bodies, a histopathological finding of Parkinson's disease. Prolyl oligopeptidase (PREP) is a serine protease that binds to alpha-synuclein and accelerates its aggregation in vitro. PREP enzyme inhibitors have been shown to block the alpha-synuclein aggregation process in vitro and in cellular models, and also to enhance the clearance of alpha-synuclein aggregates in transgenic mouse models. Moreover, PREP inhibitors have induced alterations in dopamine and metabolite levels, and dopamine transporter immunoreactivity in the nigrostriatal tissue. In this study, we characterized the role of PREP in the nigrostriatal dopaminergic and GABAergic systems of wild-type C57Bl/6 and PREP knockout mice, and the effects of PREP overexpression on these systems. Extracellular concentrations of dopamine and protein levels of phosphorylated dopamine transporter were increased and dopamine reuptake was decreased in the striatum of PREP knockout mice, suggesting increased internalization of dopamine transporter from the presynaptic membrane. Furthermore, PREP overexpression increased the level of dopamine transporters in the nigrostriatal tissue but decreased phosphorylated dopamine transporters in the striatum in wild-type mice. Our results suggest that PREP regulates the function of dopamine transporter, possibly by controlling the phosphorylation and transport of dopamine transporter into the striatum or synaptic membrane.Peer reviewe

Mice Deficient in Transmembrane Prostatic Acid Phosphatase Display Increased GABAergic Transmission and Neurological Alterations

Peer reviewe

High road mortality during female-biased larval dispersal in an iconic beetle

Abstract Animals often disperse from one habitat to another to access mates or suitable breeding sites. The costs and benefits of such movements depend, in part, on the dispersing individuals’ phenotypes, including their sex and age. Here we investigated dispersal and road-related mortality in larvae of a bioluminescent beetle, the European common glow-worm, Lampyris noctiluca, in relation to habitat, sex and proximity of pupation. We expected these variables to be relevant to larval dispersal because adult females are wingless, whereas adult males fly when searching for glowing females. We found that dispersing glow-worm larvae were almost exclusively females and close to pupation. The larvae were often found on a road, where they were able to move at relatively high speeds, with a tendency to uphill orientation. However, each passing vehicle caused a high mortality risk, and we found large numbers of larvae run over by cars, especially close to covered, forest-like habitat patches. In contrast, adult females in the same area were most often found glowing in more open rocky and grassy habitats. These findings demonstrate an underappreciated ecological strategy, sex-biased dispersal at larval phase, motivated by different habitat needs of larvae and wingless adult females. The results are also consistent with roads being an ecological trap, facilitating dispersal and presumably females’ signal visibility but causing severe larval mortality just before the reproductive stage. Hence, in addition to the previously recognised threats of urbanisation, even low traffic volumes have a high potential to negatively affect especially females of this iconic beetle

Immunofluorescent colocalization stainings of TMPAP and synaptic vesicle associated proteins.

<p>TMPAP (green) is colocalized with a presynaptic marker, synaptophysin (red) (A–C; yellow color and white arrows depicting the colocalization). PAP was seen in vesicle-like structures that had strong colocalization with Snapin (D–F). Small picture is a magnification from panel C, depicting the colocalization. Moreover, largest PAP-immunoreactive structures had a colocalization with multivesicular bodies (MVB, red; G–I). All pictures are from striatum. Scale bars are 10 µm in A–C and G–I, and 3 µm in D–F.</p

The colocalization of PAP (green) and GAD65/67 (red) was seen in several areas of brain.

<p>In cerebral Purkinje cells (A–C), strong colocalization was seen especially in the axon hillock of the neuron (small picture in C; yellow color and white arrows depicting the colocalization). Similarly, PAP was present in GABAergic neurons in prefrontal cortex (PFC; infralimbic cortex) (D–F). Scale bars are 10 µm.</p

TMPAP is expressed in the mouse brain and colocalizes with GABAergic marker, GAD 65/67.

<p>Representative confocal images depict intense TMPAP (brown color) expression in molecular cell layer (M) and Purkinje cells (P) of cerebellum (Panel A), in substantia nigra pars reticulata (SNpr; Panel B), in red nucleus (RN; Panel C) and in oculomotor nucleus (O; Panel C). Small picture in Panel B depicts the TMPAP staining of the substantia nigra in PAP<i>^−/−</i> mouse. TMPAP (green) was colocalized with GABAergic marker (red) in medium spiny neurons of striatum (Panels D-G, yellow color and white arrows indicating the colocalization) and in SNpr (Panels H–K). Colocalization was evident also in GABAergic neurons of hippocampus CA1 (Panels L–O). DAPI (blue color) was used as a nuclear marker. Scale bars are 500 µm in Panels A–C, and 10 µm in panels D–O.</p

Anatomical, neurochemical and behavioral characterization of mice deficient in prostatic acid phosphatase (PAP).

<p><b>ABBREVIATIONS:</b> NSD - no significant difference; ↑- increased; DA - dopamine; DOPAC - 3,4-Dihydroxyphenylacetic acid; GABAA - GABAA receptor; mIPSC - miniature inhibitory postsynaptic current; LORR - loss of righting reflex; PPI - prepulse inhibition; EPM - elevated plus-maze; OF - open field; LD - light-dark box; RR - rota-rod; BW - beam walking; FST - forced swim test; TST - tail suspension test; FC - fear conditioning; RI - resident-intruder test; WM - water maze.</p

Dopamine synthesis is augmented in the striatum of PAP<i>^−/−</i> mice.

<p>(A) Tissue levels of DA are similar in WT and PAP<i>^−/−</i> mice. (B) Level of the principal metabolite of DA, DOPAC, is elevated in the PAP<i>^−/−</i> mice, and also the DOPAC/DA ratio is elevated (C). (D) Accumulation of L-DOPA is greater in PAP^−/− mice than WT mice 30 min after administration of a blocker of L-amino acid decarboxylase, indicating increased DA synthesis. The data is expressed as mean±S.E.M.; black bars represent WT, grey bars PAP^−/− mice; *<i>p</i><0.05, two tailed t-test (monoamines) or repeated measures ANOVA (microdialysis).</p

Lateral ventricles volume is enlarged in PAP^−/− mice.

<p>Lateral ventricles (right and left ventricles) volume is significantly larger (**<i>p</i><0.01) in both young and old PAP<i>^−/−</i> mice compared to corresponding WT mice. (A) T2-weighted images from young (2 months) and old (12 months) WT and PAP<i>^−/−</i> mice. Plot of (B) lateral ventricle volumes and (C) total brain size for WT and PAP<i>^−/−</i> mice. The data is expressed as mean±S.E.M.</p