MPTP toxicity causes vocal, auditory, orientation and movement defects in the echolocation bat

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can damage dopaminergic neurons in the substantia nigra in many mammals with biochemical and cellular changes that are relatively similar to those observed in Parkinson's disease. Our study examined whether MPTP-treated echolocation bats can cause changes in bat echolocation system. By considering ultrasound spectrums, auditory brainstem-evoked potentials and flight trajectories of normal bats, we observed that the vocal, auditory, orientation and movement functions of MPTP-treated bats were significantly impaired, and they exhibited various symptoms resembling those in patients with Parkinson's disease. Our immunohistochemistry and western blot analyses further indicated that expression of vocal-related FOXP2 in the superior colliculus, auditory-related otoferlin in the inferior colliculus, dopamine synthesis-related aromatic l-amino acid decarboxylase in the substantia nigra and dopamine receptor in the striatum was significantly decreased. Furthermore, protein expression related to inflammation, oxidative stress and apoptosis in the substantia nigra was significantly increased in MPTP-treated bats. These results indicate that inflammation, oxidative stress and apoptosis may be instrumental in dopaminergic neurodegeneration in the substantia nigra. The vocal, auditory and orientation and movement dysfunctions of MPTP-treated bats are relatively consistent with symptoms of Parkinson's disease.

Atomoxetine improves attentional orienting in a predictive context

The role of norepinephrine (NE) in visuo-spatial attention remains poorly understood. Our goal was to identify the attentional processes influenced by atomoxetine (ATX) injections, a NE-reuptake inhibitor that boosts the level of NE in the brain, and to characterize these influences. We tested the effects of ATX injections, on seven monkeys performing a saccadic cued task in which cues and distractors were used to manipulate spatial attention. We found that when the cue accurately predicted the location of the upcoming cue in 80% of the trials, ATX consistently improved attentional orienting, as measured from reaction times (RTs). These effects were best accounted for by a faster accumulation rate in the valid trials, rather than by a change in the decision threshold. By contrast, the effect of ATX on alerting and distractor interference was more inconsistent. Finally, we also found that, under ATX, RTs to non-cued targets were longer when these were presented separately from cued targets. This suggests that the impact of NE on visuo-spatial attention depends on the context, such that the adaptive changes elicited by the highly informative value of the cues in the most frequent trials were accompanied by a cost in the less frequent trials.

Effects of methamphetamine abuse on spatial cognitive function

Methamphetamine (MA) abuse has been rising rapidly over the past decade, however, its impact in spatial cognitive function remains unknown. To understand its effect on visuospatial ability and spatial orientation ability, 40 MA users and 40 non-MA users conducted the Simple Reaction Task (Task 1), the Spatial Orientation Task (Task 2), and the Mental Rotation Task (Task 3), respectively. There was no significant difference in either accuracy or reaction time (RT) between 2 groups in Task 1. During Task 2, in comparison with non-MA users, MA users performed poorer on RT, but not in accuracy for foot and hand stimuli. In addition, both non-MA and MA users responded much more quickly to upward stimuli than downward stimuli on vertical surface, however, only non-MA users exhibited leftward visual field advantage in horizontal orientation processing. As for Task 3, MA users exhibited poorer performance and more errors than their healthy counterparts. For each group, linear relationship was revealed between RT and orientation angle, whereas MA abuse led to longer intercept for all stimuli involved. Our findings suggested that MA abuse may lead to a general deficit in the visuospatial ability and the spatial orientation ability with more serious impact in the former.

Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird

Birds that travel long distances between their wintering and breeding grounds may be particularly susceptible to neurotoxic insecticides, but the influence of insecticides on migration ability is poorly understood. Following acute exposure to two widely used agricultural insecticides, imidacloprid (neonicotinoid) and chlorpyrifos (organophosphate), we compared effects on body mass, migratory activity and orientation in a seed-eating bird, the white-crowned sparrow (Zonotrichia leucophrys). During spring migration, sparrows were captured, held and dosed by gavage daily for 3 days with either the vehicle control, low (10% LD50) or high (25% LD50) doses of imidacloprid or chlorpyrifos and tested in migratory orientation trials pre-exposure, post-exposure and during recovery. Control birds maintained body mass and a seasonally appropriate northward orientation throughout the experiment. Imidacloprid dosed birds exhibited significant declines in fat stores and body mass (mean loss: -17% low, -25% high dose) and failed to orient correctly. Chlorpyrifos had no overt effects on mass but significantly impaired orientation. These results suggest that wild songbirds consuming the equivalent of just four imidacloprid-treated canola seeds or eight chlorpyrifos granules per day over 3 days could suffer impaired condition, migration delays and improper migratory direction, which could lead to increased risk of mortality or lost breeding opportunity.

Dimethyl Sulfide is a Chemical Attractant for Reef Fish Larvae

Transport of coral reef fish larvae is driven by advection in ocean currents and larval swimming. However, for swimming to be advantageous, larvae must use external stimuli as guides. One potential stimulus is "odor" emanating from settlement sites (e.g., coral reefs), signaling the upstream location of desirable settlement habitat. However, specific chemicals used by fish larvae have not been identified. Dimethyl sulfide (DMS) is produced in large quantities at coral reefs and may be important in larval orientation. In this study, a choice-chamber (shuttle box) was used to assess preference of 28 pre-settlement stage larvae from reef fish species for seawater with DMS. Swimming behavior was examined by video-tracking of larval swimming patterns in control and DMS seawater. We found common responses to DMS across reef fish taxa - a preference for water with DMS and change in swimming behavior - reflecting a switch to "exploratory behavior". An open water species displayed no response to DMS. Affinity for and swimming response to DMS would allow a fish larva to locate its source and enhance its ability to find settlement habitat. Moreover, it may help them locate prey accumulating in fronts, eddies, and thin layers, where DMS is also produced.

Acyl ghrelin improves cognition, synaptic plasticity deficits and neuroinflammation following amyloid β (Aβ1-40) administration in mice

Ghrelin is a metabolic hormone that has neuroprotective actions in a number of neurological conditions, including Parkinson's disease (PD), stroke and traumatic brain injury. Acyl ghrelin treatment in vivo and in vitro also shows protective capacity in Alzheimer's disease (AD). In the present study, we used ghrelin knockout (KO) and their wild-type littermates to test whether or not endogenous ghrelin is protective in a mouse model of AD, in which human amyloid β peptide 1-40 (Aβ_1-40 ) was injected into the lateral ventricles i.c.v. Recognition memory, using the novel object recognition task, was significantly impaired in ghrelin KO mice and after i.c.v. Aβ_1-40 treatment. These deficits could be prevented by acyl ghrelin injections for 7 days. Spatial orientation, as assessed by the Y-maze task, was also significantly impaired in ghrelin KO mice and after i.c.v. Aβ_1-40 treatment. These deficits could be prevented by acyl ghrelin injections for 7 days. Ghrelin KO mice had deficits in olfactory discrimination; however, neither i.c.v. Aβ_1-40 treatment, nor acyl ghrelin injections affected olfactory discrimination. We used stereology to show that ghrelin KO and Aβ_1-40 increased the total number of glial fibrillary acidic protein expressing astrocytes and ionised calcium-binding adapter expressing microglial in the rostral hippocampus. Finally, Aβ_1-40 blocked long-term potentiation induced by high-frequency stimulation and this effect could be acutely blocked with co-administration of acyl ghrelin. Collectively, our studies demonstrate that ghrelin deletion affects memory performance and also that acyl ghrelin treatment may delay the onset of early events of AD. This supports the idea that acyl ghrelin treatment may be therapeutically beneficial with respect to restricting disease progression in AD.

NEUROPROTECTIVE ACTION OF PHENIBUT AND NEUROGLUTAM IN EXPERIMENTAL CEREBRAL ISCHEMIA ON THE BACKGROUND OF ALTERED IMMUNOREACTIVITY

Cerebroprotective activity of phenyl derivatives of GABA (phenibut, 25 mg/kg) and L-glutamic acid (neuroglutam, 26 mg/kg) in rats with cerebral ischemia was studied on the background of intact and altered immunoreactivity. Tested compounds were administered intraperitoneally for 7 days after two phase ligation of common carotid arteries (second artery was ligated 3 days after ligation of the first artery). Immunosuppression caused by cyclosporin (daily dose 5 mg/kg, p.o., for 13 days) worsened brain ischemia outcome, as manifested by increased mortality, more severe neurological marker score, increased levels of brain damage markers (NSE and MBP) in the blood serum, decrease in muscle strength and locomotor activity, and impairment of orientation and research activity as compared to animals with brain ischemia and intact immunity. Activation of immune system was caused by lipopolysaccharide (10 mg/kg, i.p., 7 injections every second day). Upon activation of the immune system, brain ischemia produced lower mortality, while the survived rats exhibited more favorable outcome of ischemia than animals with suppression of immune system: lover neurological marker score, lower blood serum NSE and MBP levels (-35% on average,p < 0.05), and much higher level of performance in motor coordination, muscular strength, and locomotor activity (+90% on average, p < 0.05). The state of immune system significantly influenced the neuroprotective activity of drugs tested. Neuroglutam administration produced positive effect both in animals with intact immunity and on the background of altered immunoreactivity. However, most positive outcome after neuroglutam administration in ischemic rats was observed in animals with suppression of immune system, with significant increase in the cerebral blood flow level (+56%), decrease in NSE and MBP blood serum levels (57 and 76%, respectively) after 7-day treatment as compared to the control group. The therapeutic potential of phenibut was somewhat lower than that of neuroglutam, and it was more pronounced in rats with activated immune system, whereas the drug effectiveness in rats with suppressed immune system was less pronounced.