Mechanisms of Avian Magnetic Orientation

Among the most fascinating mysteries of life is the interaction between biological systems and the earth’s magnetic field. Although earth’s magnetism may have an under appreciated role in biological interpretations, it has been most extensively studied in the processes of avian orientation and migration. Many species of bird are known to have behavioral responses to the earth’s and artificial magnetic fields. These responses may be mediated by a number of potential magneto-biochemical processes. The two most commonly investigated include a magnetosensitive magnetite rich region in the upper beak area and a photo/magnetoreception process in the eyes of various bird species. In addition to external magnetic stimuli, recent findings in visually restricted birds have described a hemispherically lateralized interpretation of this information within the brain. Even with these findings, a considerable amount of work is needed to clarify what information is processed and how it is used to create the bird’s magnetic compass. This review focuses these recently published findings as a means to assess this intriguing phenomenon

Severe dopaminergic neuron loss in rhesus monkey brain impairs morphine-induced conditioned place preference

It is well known that dopamine is critical for reward, but the precise role of dopamine in reward remains uncertain. The aim of this study was to determine what percentage of dopaminergic neurons in the primate brain is required for the expression of conditioned reward by measuring the performance of dopamine-deficient rhesus monkeys in a morphine-induced conditioned place preference paradigm. Animals with mild Parkinsonian symptoms successfully developed and retained a morphine preference that was equivalent to control monkeys. However, these monkeys could not maintain the preference as well as controls when they retained severe Parkinsonian symptoms. On the other hand, monkeys initially in a severe Parkinsonian state developed a preference for morphine, but this preference was weaker than that of the controls. Histological results showed that the loss of dopaminergic neurons in monkeys that had severe Parkinsonian symptoms was about 80% in comparison to the control monkeys. All these data suggest that a severely impaired dopamine system alters rewarding-seeking behavior in non-human primates

Deficits in Water Maze Performance and Oxidative Stress in the Hippocampus and Striatum Induced by Extremely Low Frequency Magnetic Field Exposure

The exposures to extremely low frequency magnetic field (ELF-MF) in our environment have dramatically increased. Epidemiological studies suggest that there is a possible association between ELF-MF exposure and increased risks of cardiovascular disease, cancers and neurodegenerative disorders. Animal studies show that ELF-MF exposure may interfere with the activity of brain cells, generate behavioral and cognitive disturbances, and produce deficits in attention, perception and spatial learning. Although, many research efforts have been focused on the interaction between ELF-MF exposure and the central nervous system, the mechanism of interaction is still unknown. In this study, we examined the effects of ELF-MF exposure on learning in mice using two water maze tasks and on some parameters indicative of oxidative stress in the hippocampus and striatum. We found that ELF-MF exposure (1 mT, 50 Hz) induced serious oxidative stress in the hippocampus and striatum and impaired hippocampal-dependent spatial learning and striatum-dependent habit learning. This study provides evidence for the association between the impairment of learning and the oxidative stress i

Effect of Electromagnetic Fields Exposure on Two Versions of Water Maze Task.

<p>The data represent the latency time to escape to a submersed platform during 4 training days, with four consecutive trials per day. Mice exposed to extremely low frequency magnetic fields (1 mT) took longer to find the platform in the two versions of the water maze compared with the other two groups (p<0.001). No significant deficit in the two versions of the task was observed in the ELF-MF (0.1 mT) exposed mice (p>0.05). Values represent means±SEM. N = 12. * indicates p<0.05.</p

The activities of CAT, GSH-PX, T-AOC and the concentration of MDA.

*<p>p<0.05.</p

Chronic effects of L-Dopa treatments on total motor scores.

<p>(A) Evolution of daily motor scores during L-Dopa treatment. Timelines are aligned such that day 0 corresponds to the day on which the MPTP intoxication was stopped for each animal. Monkeys in group I received L-Dopa from day 1 and scores were taken from recordings prior to the daily L-Dopa administration. Significant differences between the two groups appeared at day 15 and continued into the later days (day 16–30). (B) Total Kurlan scores on day 31 of the two groups. Monkeys in group I received L-Dopa and displayed improvement in their total PD scores compared with the control group. Group I, n = 2; group II, n = 3. ^*P< 0.05, ^**P<0.001. Data are presented as mean ± SEM.</p

Behavioral scores of tremor, imbalance, bradykinesia and defensive reaction in the two groups before and after the administration of morphine or L-Dopa.

<p>Behavioral measurements were taken before and immediately after the administration of drug. (A) Behavioral scores after an acute dose of morphine. Tremor and loss of balance were significantly attenuated, while bradykinesia became much more prominent in group II monkeys. (B) Behavioral scores after the first dose of L-Dopa. Monkeys in group I displayed short-term amelioration of bradykinesia and defensive reaction on the first day of L-Dopa therapy. Tremor did not statistically change. (C) Behavioral scores after the last dose of L-Dopa. Monkeys in group I received L-Dopa treatments for 31 days and displayed amelioration of bradykinesia and defensive reaction on the last day (day 31) of L-Dopa therapy. No significant differences were found for tremor. Group I, n = 2; group II, n = 3. ^**P<0.001. Data are presented as mean ± SEM.</p

The Antioxidatant Status in Mice Hippocampus and Striatum.

<p>After extremely low frequency magnetic field (ELF-MF) exposure for consecutive 12 weeks, the antioxidatant status in mice hippocampus and striatum was impaired by ELF-MF exposure (1 mT) but not by ELF-MF exposure (0.1 mT). Values represent means±SEM. N = 12. * indicates p<0.05.</p

The appearance of individual PD symptoms in monkeys given MPTP intoxication.

<p>This graph presents the average day of appearance for each symptom. Error bars indicate the SEM for appearance of each symptom (n = 5).</p