Kappa Opioid Receptor Antagonism Rescues Genetic Perturbation of Dopamine Homeostasis: Molecular, Physiological and Behavioral Consequences.

Aberrant dopamine (DA) signaling is implicated in schizophrenia, bipolar disorder (BPD), autism spectrum disorder (ASD), substance use disorder, and attention-deficit/hyperactivity disorder (ADHD). Treatment of these disorders remains inadequate. We established that the human DA transporter (DAT) coding variant (DAT Val559), identified in individuals with ADHD, ASD, or BPD, exhibits anomalous DA efflux (ADE) that is blocked by therapeutic amphetamines and methylphenidate. As the latter agents have high abuse liability, we exploited DAT Val559 knock-in mice to identify non-addictive agents that can normalize DAT Val559 functional and behavioral effects ex vivo and in vivo. Kappa opioid receptors (KORs) are expressed by DA neurons and modulate DA release and clearance, suggesting that targeting KORs might offset the effects of DAT Val559. We establish that enhanced DAT Thr53 phosphorylation and increased DAT surface trafficking associated with DAT Val559 expression are mimicked by KOR agonism of wildtype preparations and rescued by KOR antagonism of DAT Val559 ex vivo preparations. Importantly, KOR antagonism also corrected in vivo DA release and sex-dependent behavioral abnormalities. Given their low abuse liability, our studies with a construct valid model of human DA associated disorders reinforce considerations of KOR antagonism as a pharmacological strategy to treat DA associated brain disorders.

Response to Hypoxic Preconditioning of Glial Cells from the Roof of the Fourth Ventricle.

The cerebellum harbors a specialized area on the roof of the fourth ventricle that is composed of glial cells and neurons that interface with the cerebrospinal fluid. This region includes the so-called ventromedial cord (VMC), which is composed of cells that are glial fibrillary acidic protein (GFAP)-positive and nestin-positive and distributes along the midline in association with blood vessels. We hypothesized that these cells should compare to GFAP and nestin-positive cells that are known to exist in other areas of the brain, which undergo proliferation and differentiation under hypoxic conditions. Thus, we tested whether cells of the VMC would display a similar reaction to hypoxic preconditioning (HPC). Indeed, we found that the VMC does respond to HPC by reorganizing its cellular components before it gradually returns to its basal state after about a week. This response we documented by monitoring global changes in the expression of GFAP-EGFP in transgenic mice, using light-sheet fluorescence microscopy (LSFM) revealed a dramatic loss of EGFP upon HPC, and was paralleled by retraction of Bergmann glial cell processes. This EGFP loss was supported by western blot analysis, which also showed a loss in the astrocyte-markers GFAP and ALDH1L1. On the other hand, other cell-markers appeared to be upregulated in the blots (including nestin, NeuN, and Iba1). Finally, we found that HPC does not remarkably affect the incorporation of BrdU into cells on the cerebellum, but strongly augments BrdU incorporation into periventricular cells on the floor of the fourth ventricle over the adjacent medulla.

Anorexia Reduces GFAP+ Cell Density in the Rat Hippocampus.

Anorexia nervosa is an eating disorder observed primarily in young women. The neurobiology of the disorder is unknown but recently magnetic resonance imaging showed a volume reduction of the hippocampus in anorexic patients. Dehydration-induced anorexia (DIA) is a murine model that mimics core features of this disorder, including severe weight loss due to voluntary reduction in food intake. The energy supply to the brain is mediated by astrocytes, but whether their density is compromised by anorexia is unknown. Thus, the aim of this study was to estimate GFAP+ cell density in the main regions of the hippocampus (CA1, CA2, CA3, and dentate gyrus) in the DIA model. Our results showed that GFAP+ cell density was significantly reduced (~20%) in all regions of the hippocampus, except in CA1. Interestingly, DIA significantly reduced the GFAP+ cells/nuclei ratio in CA2 (-23%) and dentate gyrus (-48%). The reduction of GFAP+ cell density was in agreement with a lower expression of GFAP protein. Additionally, anorexia increased the expression of the intermediate filaments vimentin and nestin. Accordingly, anorexia increased the number of reactive astrocytes in CA2 and dentate gyrus more than twofold. We conclude that anorexia reduces the hippocampal GFAP+ cell density and increases vimentin and nestin expression.

Ectoparasite Raymondia lobulata infestation in relation to the reproductive cycle of its host--the greater false vampire bat Megaderma lyra.

To study variation of infestations by the bat fly Raymondia lobulata (Diptera: Streblidae) on the greater false vampire bat Megaderma lyra (Chiroptera: Megadermatidae), we captured individual bats at their day roost in the south of India and recorded their rate of infestation continuously for a year. All examined bats (n = 72 individuals, 202 captures) were infested with parasites (n = 3,008). However, the recorded intensity of infestation (range 1-33) was gender-related and statistically higher in females than in males (F(1, 200) = 304.45, P < 0.001). Furthermore, pregnant and lactating females had greater parasite loads than non-reproductive females and males (F(1, 63) = 23.34, P < 0.001 and F(1, 37) = 78.07, P < 0.001, respectively). No significant differences were observed between males either during mating and non-mating periods or breeding and non-breeding seasons. Analysis of the relationship between parasite infestation and the reproductive status of bats revealed that pregnant and lactating females with pups were more vulnerable hosts for parasites. Our results also suggest a well-developed coevolutionary strategy for synchronized reproduction within the host-parasite relationship and add to our understanding of how host sex and reproductive status shape the dynamics of parasitism.