What’s special about the ethical challenges of studying disorders with altered brain activity?

Where there is no viable alternative, studies of neuronal activity are conducted on animals. The use of animals, particularly for invasive studies of the brain, raises a number of ethical issues. Practical or normative ethics are enforced by legislation, in relation to the dominant welfare guidelines developed in the UK and elsewhere. Guidelines have typically been devised to cover all areas of biomedical research using animals in general, and thus lack any specific focus on neuroscience studies at the level of the ethics, although details of the specific welfare recommendations are different for invasive studies of the brain. Ethically there is no necessary distinction between neuroscience and other biomedical research in that the brain is a final common path for suffering, irrespective of whether this involves any direct experience of pain. One exception arises in the case of in vitro studies, which are normally considered as an acceptable replacement for in vivo studies. However, to the extent sentience is possible, maintaining central nervous system tissue outside the body naturally raises ethical questions. Perhaps the most intractable challenge to the ethical use of animals in order to model neuronal disorder is presented by the logical impasse in the argument that the animal is similar enough to justify the validity of the experimental model, but sufficiently different in sentience and capacity for suffering, for the necessary experimental procedures to be permissible

Electroretinographic evaluation of spectral sensitivity in yellow and silver eels (Anguilla anguilla)

Although differences in visual pigments between developmental stages of the European eel are well known, the expected differences in spectral sensitivity have not been demonstrated at the electrophysiological level. In fact, one past electroretinographic study led to the conclusion that in eels there is no change in scotopic sensitivity, with increasing sexual maturity. In the present experiments, electroretinograms (ERGs) were recorded from in situ eyecups of immobilized eels Anguilla anguilla (L.) caught in coastal running waters. It was shown that the ERG b-wave is as good an indicator of spectral sensitivity as the unmasked late receptor potential (LRP) which directly reflects the responsiveness of photoreceptors. Complete spectral-sensitivity curves, based on b-wave thresholds and on thresholds of LRP subsequently isolated by means of sodium iodate, have been obtained in the same eel. Using fitted amplitude-log intensity functions for threshold calculation, and two models for computer-assisted fitting of spectral-sensitivity curves, significant differences in lambda(max) were found between yellow and silver developmental stages of the eel, identified by ocular index measurements

Effects of xanthine derivatives on electroretinographic responsiveness

In view of the use of synthetic propentofylline (PPF) as a protective agent in brain ischemia, its possible side effects on vision capacities have been explored by electroretinography in comparative experiments with theophylline. We used eyecup preparations of small-spotted dogfish sharks and of European eels, particularly ly suitable for long-lasting experiments. The drug exerted profound but reversible modifications of ERG records: (1) a dose-dependent increase of the amplitude and duration of the chemically isolated late receptor potential (LRP), (2) a partial unmasking of LRP, (3) a strong potentiation of the LRP-unmasking effect of low temperature, (3) a potentiation of light adaptation effects, and (5) a strong potentiation of the post-illumination hyperexcitability. The effects were explicable as due to a strong phosphodiesterase (PDE) inhibiting, cyclic guanosine monophosphate (cGMP) promoting, action of the drug. The effects were considerably stronger, or even of opposite sign, in comparison to those of the chemically related theophylline. PPF did not seriously affect the ERG c-wave originating in the pigment epithelium. The results suggested that the effects of PPF on vision may not seriously hamper the therapeutic use of the drug. They indicated, on the other hand, that PPF was a retinoactive drug of potential usefulness in the exploration of the complex biochemical events underlying visual transduction

Feeding habits of huchen Hucho hucho (Salmonidae) fry in the River Tresnjica, Yugoslavia

About 10 000 huchen larvae, obtained by artificial spawning, were introduced on 28 May 1995 into the River Tresnjica, a tributary to the River Drina, using procedures applied routinely by local fishing associations. During next two months, only 33 fry were caught in the river. Nevertheless, valuable information has been obtained for the first time on young huchens in the Drina basin. The fry apparently selected slower or almost stagnant water habitats outside the main river course. The variability of prey organisms found in fry stomachs decreased with fry length. Larger and particularly motile prey, especially mayfly larvae, gradually dominated the fry diet. Also for the first time, we document homing instinct in huchons with mark-recapture information: one out of the nine adults, tagged after spawning, was recaptured the following year at the same spawning site

Influence of photic environment on the form of the fish electroretinographic off-response

Scotopic electroretinogram of dogfish shark (Scylliorhinus canicula) and eel (Anguilla anguilla) is characterized by a negative off-response, changing in sign under photopic condition. It increased under the effect of increased background illumination, but its amplitude never exceeded that of the b-wave. On the other hand, dark-adapted electroretinograms of two perch-like species, perch (Perca fluviatilis) and painted comber (Serranus scriba), exhibited a positive off-wave, exceeding the b-wave amplitude under bright photopic conditions

Modeling of the migration of the European glass eel

The characteristics of glass eel migration at the mouth of river Bojana have been investigated by seasonal field studies from February to April 1998. Samples were collected by two fyke nets, one on each riverside, for 12 hours each night. A total of about 3,300 individuals were caught. In this work we present the results obtained from three successive migration waves in 1998. The data obtained on the number of eels caught during one migration wave, as a function of time, had two components: a bell-shaped curve, lasting 7-14 days, over which an impulse (sudden burst in the number of caught eels, during 1-2 days) was observed. We propose a mathematical model for total number of captured eels within one migration wave. Impulse components were observed during the first and second migration waves. After their removal, the remaining experimental data of the three migration waves were fitted with normal distribution functions. A decrease in the values of fitting parameters as a function of time (migration wave number) was obtained. Our data indicate multiple causes for the observed migration waves

Electrophysiological and spectral properties of second-order retinal neurons in the eel

Several classes of second-order neurons have been electrophysiologically explored in immature European eels (Anguilla anguilla) from two distant and ecologically different localities tin Russia and Yugoslavia). The majority of L-horizontal cells (58 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Spectral sensitivity characteristics of a number of horizontal and bipolar cells indicated that yellow-sensitive and green-sensitive cones coexist in the retina of the European eel, and that rods and green-sensitive cones contain similar visual pigments. Pronounced color-opponent properties, often taken as the capacity of color vision, were identified in one amacrine cell, apparently of the B/Y (or B/G) type. Differences in retinal structure and responsiveness between eels from the two localities, presumably due to differences in local conditions for growth, were less important than between eels of the yellow and silver stage

Photopic vision in eels - Evidences of color discrimination

Several classes of second-order retinal neurons have been studied electrophysiologically in European eel (Anguilla anguilla) from two different localities, Lake Seliger in Russia and the coastal waters of the Adriatic Sea in Montenegro. The majority of L-horizontal cells (68 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Pronounced color-opponent properties, often taken as pointing to the capacity of color vision, were identified in one amacrine cell, apparently of the "blue/yellow" (or "blue/ green") type. Microspectrophotometric measurements revealed two different spectral classes of cones with absorption maxima at about 525 and 434 nm. The existence of green-sensitive and blue-sensitive cone units was thus revealed by both electrophysiological and microspectrophotometric techniques