Biomedical subjects

S Winberg

Publications and source records attributed to S Winberg.

18 recordsLinked to original sources

PubMed2000

Intermale competition in sexually mature arctic charr: effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior.

Sexually mature Arctic charr (Salvelinus alpinus) males were allowed to interact in pairs for 4 days in the absence of females. Agonistic behavior was quantified, and at the end of the experiment, plasma levels of glucose, cortisol, testosterone (T), 11-ketotestosterone (11-KT), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha, 20beta-P) were determined alongside brain concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA, the major 5-HT metabolite), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC, a major DA metabolite). Plasma cortisol and glucose were significantly elevated in subordinate fish, and the number of aggressive acts received showed positive correlations with plasma levels of glucose on day 1, during the development of the dominance relationship, and of cortisol on day 4, when the dominance relationship was established. In contrast, plasma concentrations of T and 11-KT were significantly higher in dominant than in subordinate males, and there was a similar tendency in plasma concentrations of 17alpha,20beta-P. Further, plasma levels of these gonadal steroids were correlated with the number of aggressive acts performed on day 4, but not with the number of aggressive acts received. The plasma cortisol concentrations did not correlate with either 5-HIAA:5-HT or DOPAC:DA ratios in any of the brain parts analyzed. Plasma glucose levels showed positive correlations with brain 5-HIAA:5-HT ratios. Negative correlations were observed between 5-HIAA:5-HT ratios in the optic tectum and between plasma levels of T, 11-KT, and 17alpha,20beta-P. Telencephalic DOPAC/DA ratios displayed a negative correlation with plasma levels of T, 11-KT, and 17alpha,20beta-P, but only in dominant males.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2000

Skin darkening, a potential social signal in subordinate arctic charr (Salvelinus alpinus): the regulatory role of brain monoamines and pro-opiomelanocortin-derived peptides.

Arctic charr were allowed to interact in groups of three for 5 days. Skin darkness was quantified by measuring the mean brightness of individual fish before and after social interaction. Brain levels of monoamines and monoamine metabolites and plasma concentrations of cortisol, adrenocorticotropic hormone (ACTH), N-acetyl-(beta)-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) were analysed. The results show that social subordination resulted in a significant skin darkening. Furthermore, plasma concentrations of alpha-MSH, ACTH and cortisol were elevated in subordinates, and these fish also displayed elevated levels of 5-hydroxyindoleacetic acid (5-HIAA) in the telencephalon. The ratio of [5-HIAA] to serotonin [5-HT] was increased in several brain areas. In addition, the ratio of 3-methoxy-4-hydroxyphenylglycol (MHPG) to norepinephrine (NE) concentrations was significantly increased in the optic tectum of subordinate fish. Skin darkness following social interaction showed a significant positive correlation with plasma levels of alpha-MSH. Plasma levels of ACTH and alpha-MSH were both positively correlated with that of cortisol. Brain [5-HIAA]/[5-HT] ratios were positively correlated with circulating plasma levels of ACTH, and a similar positive correlation was seen between [MHPG]/[NE] ratios in the optic tectum and plasma levels of ACTH, alpha-MSH and N-acetyl-beta-endorphin. In contrast, hypothalamic [MHPG]/[NE] ratios displayed a negative correlation with plasma alpha-MSH concentrations. The present study demonstrates that social stress induces skin darkening in Arctic charr and that this effect could be mediated by a stress-induced increase in the levels of alpha-MSH in the circulation. Furthermore, the results suggest that 5-HT and NE in the central nervous system could be factors regulating the pituitary release of ACTH and alpha-MSH.

Adrenocorticotropic Hormone↗

PubMed1999

Relationships between sex and the size and number of forebrain gonadotropin-releasing hormone-immunoreactive neurones in the ballan wrasse (Labrus berggylta), a protogynous hermaphrodite.

This study is the first to examine the brain gonadotropin-releasing hormone (GnRH) cell population phenotype in a protogynous and monandric sequentially hermaphroditic fish. Male ballan wrasse (Labrus berggylta) had on average higher numbers of GnRH-immunoreactive (GnRH-ir) cells within the brain preoptic area (POA) than females, a difference not found in GnRH-ir cells in other brain regions. Furthermore, in males, but not females, the number of these POA GnRH-ir cells correlated with body size. Maturational state (prespawning or postspawning) had marked effects on mean profile sizes (but not numbers) of both GnRH-ir cell bodies and cell nuclei, even when existing differences in body size and allometric relationships had been taken into account. Postspawning males tended to have larger GnRH-ir profiles in all brain regions relative to both prespawning males and females. Moreover, the GnRH-ir cell number in POA, and the cell body profile size in both POA and at the level of the anterior commissure, correlated with gonad size in spermiated prespawning males, indicating a relationship between both size and number of GnRH cells and male gonadal development. These results suggest that temporary changes in the size of brain GnRH-ir neurones are coupled to the male spawning cycle, and that permanent POA GnRH-ir cell number changes are involved in the process of sex change in sequential hermaphrodites. However, smaller males had no more preoptic GnRH-ir cells than equally sized females, which may argue against a proximate inducing role of GnRH cell number changes in naturally occurring sex reversal.

Animals↗

PubMed1999

Short-term effects of fights for social dominance and the establishment of dominant-subordinate relationships on brain monoamines and cortisol in rainbow trout.

We report changes in brain serotonergic, noradrenergic and dopaminergic activity, along with plasma cortisol concentrations, occurring during the initial 24-h period following the establishment of dominant-subordinate relationships in pairs of rainbow trout. Immediately (within 5 min) after the termination of staged fights for social dominance, a large increase in blood plasma cortisol was observed in both fight losers (future subordinate fish) and winners (future dominant fish). In dominant fish, cortisol decreased rapidly (within 3 h) to the level of unstressed controls, while continuing to increase in subordinate fish. At 3 h following fights, the brain serotonergic system was activated in both dominant fish and subordinate fish, at least in some brain regions (telencephalon). This effect was reversed in dominant individuals within 24 h of social interaction, whereas in subordinate fish a substantial activation of the serotonergic system was manifest in all brain regions by 24 h. Similarly, a strong increase in brain catecholaminergic activation was indicated after 24 h of social interaction in subordinate fish, but not in dominant fish. Relationships between plasma cortisol and brain serotonergic and noradrenergic activity in the various experimental groups suggest that these systems influence cortisol secretion under normal conditions and during moderate or short-term stress.

Aggression↗

PubMed1998

Elevation of brain 5-HT activity, POMC expression, and plasma cortisol in socially subordinate rainbow trout.

Agonistic behavior, brain concentrations of serotonin (5-hydroxytryptamine, 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA, the main 5-HT metabolite), plasma cortisol levels, and the pituitary expression of pro-opiomelanocortin (POMC) A and B mRNA were determined in socially dominant and subordinate rainbow trout after 1 or 7 days of social interaction. Telencephalic and brain stem 5-HIAA/5-HT ratios, plasma cortisol levels, and pituitary POMC mRNA concentrations were elevated in fish being subordinate for 1 day. Furthermore, neither telencephalic 5-HIAA/5-HT ratios nor pituitary POMC A or POMC B mRNA expression showed any decline after 7 days of social interaction. By contrast, plasma cortisol concentrations of subordinate fish declined after 7 days but were still significantly higher than in dominant fish. Furthermore, in subordinate fish, hypothalamic 5-HIAA/5-HT ratios and plasma cortisol levels were highly correlated, suggesting an important role of hypothalamic 5-HT in the regulation of the teleost hypothalamic-pituitary-interrenal (HPI) axis. The number of aggressive acts received and plasma cortisol levels were highly correlated in 1-day subordinates, a relationship not seen in fish subjected to 1 wk of subordination. Thus the chronic stress experienced by subordinates in established dominance hierarchies appears to be more closely related to the threat imposed by the presence of the dominant fish than to actual aggressive encounters. The sustained elevation of pituitary POMC mRNA expression, an effect mainly related to an increase of melanotropic POMC expression, in subordinates could be a mechanism serving to maintain HPI axis excitability and promote acclimation in these individuals.

Animals↗

PubMed1997

Serotonin as a regulator of hypothalamic-pituitary-interrenal activity in teleost fish.

Evidence for the presence of a serotonin1A (5-HT1A) receptor subtype in the salmonid fish brain has recently been presented. In the present study the potent 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) was tested for its effect on plasma cortisol concentrations in rainbow trout (Oncorhynchus mykiss). Blood was sampled and 8-OH-DPAT administered through a catheter in the dorsal aorta. Thirty minutes after the injection of 40 microg of 8-OH-DPAT/kg, plasma cortisol levels had increased from 12 to 149 ng/ml, whereupon they fell, reaching baseline levels after 4 h. The effect of 1-40 microg 8-OH-DPAT/kg on plasma cortisol concentrations was dose-dependent. The results lends further support to the hypothesis that the brain serotonergic system plays a key role in integrating autonomic, behavioral and neuroendocrine stress-responses in fish as well as mammals, suggesting that not only the structural and biochemical organization, but also the function of the serotonergic system has been conserved during vertebrate evolution.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1997

Effects of L-thyroxine on brain monoamines during parr-smolt transformation of Atlantic salmon (Salmo salar L.).

During spring, seaward migrating juvenile Atlantic salmon (Salmo salar) undergo parr-smolt transformation (PST) which involves changes in physiology, including one or two peaks in plasma thyroxine (T4). To investigate if changes in plasma T4 influence neural function, we measured levels of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and also measured serotonin (5-hydroxytryptamine, 5-HT) and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA) in brain regions of two groups of Atlantic salmon parr on an 8:16 h light/dark photoperiod. One group was treated with ambient T4 to simulate the natural smolt peak in plasma T4. T4 treatment depressed DOPAC levels as well as DOPAC/DA and 5-HIAA/5-HT ratios in the olfactory system but with no changes in the optic tectum. We conclude that during PST monoaminergic functions in specific brain regions of juvenile Atlantic salmon are affected by T4 treatment.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Number of preoptic GnRH-immunoreactive cells correlates with sexual phase in a protandrously hermaphroditic fish, the dusky anemonefish (Amphiprion melanopus).

The populations of gonadotropin-releasing hormone (GnRH)-producing cells within the preoptic area (POA) and terminal nerve (TN) of the brain have been suggested as the neuronal systems mediating social control of sex and gonadogenesis in sequentially hermaphroditic teleosts. In the present study, the number and soma size of GnRH-immunoreactive (GnRH-ir) cells in the POA and TN were studied in male, female and juvenile individuals of the dusky anemonefish (Amphiprion melanopus), a species which displays both male to female sex change and socially controlled sexual maturation. The results showed that the number of POA (but not TN) GnRH-ir cells differ significantly between sexual phases, with males displaying higher cell numbers than both females and juveniles. Soma sizes of POA and TN GnRH-ir cells were larger in females than in males and juveniles. However, this relationship was fully explained by differences in body size. The results indicate that high POA GnRH cell numbers are part of a masculinizing mechanism and support the hypothesis that the POA GnRH cell population plays a central role in initiating or mediating the process of socially induced gonadal and/or behavioural transformations in sequential hermaphrodites.

Animals↗

PubMed1997

Effect of social rank on brain monoaminergic activity in a cichlid fish.

In Haplochromis burtoni, an African cichlid fish, male sexual maturation is regulated via social interactions, and these effects are mediated by gonadotropin-releasing-hormone (GnRH)-containing neurons in the preoptic area of the brain. Since brain monoaminergic systems are known to be involved in the regulation of GnRH release, and the activity of these systems is influenced by agonistic interactions, we analyzed the effect of social status on brain monoaminergic activity in H. burtoni. Animals were either (1) in normal social groups consisting of two males and four females or (2) in groups of one male and five females. Quantitative behavioral observations were made on each group of animals and, following sacrifice several physiological measurements were made. Concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA, the main 5-HT metabolite) and tryptophan (TRP, the amino acid precursor of 5-HT), dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC, the main DA metabolite) were measured. The 5-HIAA/5-HT and DOPAC/DA ratios were calculated and used as indexes of 5-HT and DA activity, respectively. In addition, the gonadosomatic index was calculated from body and gonadal weights and used as an index of reproductive status. Concentrations of 5-HIAA as well as 5-HIAA/5-HT ratios were significantly higher in the brainstem of non-territorial males than in that of territorial males, and similar trends were seen in the telencephalon and hypothalamus. Moreover, TRP concentrations in the telencephalon and brainstem were significantly lower in non-territorial males. In this species, sexual maturation in females is not socially regulated, and there was no significant correlation between measured antagonistic behavior and biochemical indices. These results suggest a fundamental difference in the neurochemical responses between male and female H. burtoni.

Agonistic Behavior↗

PubMed1996

Agonistic interactions affect brain serotonergic activity in an acanthopterygiian fish: the bicolor damselfish (Pomacentrus partitus).

Bicolor damselfish were allowed to interact in pairs for 15 min a day during a five-day period. Agonistic behaviour was quantified, and at the end of the experimental series, concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and tryptophan (TRP, the amino acid precursor of 5-HT) were measured, and 5-HIAA/5-HT ratios (an index of 5-HT activity) were calculated in the telencephalon, hypothalamus and brain stem. Socially interacting fish, dominant as well as subordinate, showed higher telencephalic 5-HIAA/5-HT ratios than isolated controls. Social interaction also decreased telencephalic TRP concentrations in subordinate fish but did not affect 5-HT concentrations in any of the brain parts. In subordinate fish, 5-HIAA/5-HT ratios in the telencephalon were positively correlated with the number of aggressive acts received. Moreover, in dominant fish 5-HIAA/5-HT ratios in the hypothalamus were positively correlated with the number of aggressive acts performed. These results indicate that the brain serotonergic system is involved in intraspecific aggression and/or stress reactions in bicolor damselfish.

Aggression↗

PubMed1996

Multiple high-affinity binding sites for

Binding of [3H]serotonin (5-HT) to membranes prepared from Arctic charr brain homogenates was most consistent with a one-site model for [3H]5-HT binding, with KD and Bmax values of 5.7±0.3 nmol l-1 and 60.7±7.3 fmol mg-1 protein, respectively. Similarly, 5-HT displacement of [3H]5-HT was best explained by a monophasic model with an apparent Ki of 4.3±0.7 nmol l-1. The ability of a number of synthetic 5-HT receptor ligands to displace [3H]5-HT was studied. 8OH-DPAT was found to interact with three [3H]5-HT binding sites, whereas buspirone, TFMPP, spiperone and mianserin all distinguish two sites. In the presence of 300 nmol l-1 buspirone, 8OH-DPAT and mianserin distinguished two [3H]5-HT binding sites, whereas spiperone interacted with only one. Moreover, 8OH-DPAT differentiated three [3H]5-HT binding sites even in the presence of 0.5 mmol l-1 GTP, making it unlikely that these sites represent different affinity states of G-protein-coupled receptors. GTP had no effect on apparent Ki values for 8OH-DPAT, but reduced the Bmax value of the high-affinity site by 60 %. GTP had a similar effect on the saturation binding curve for [3H]5-HT, reducing Bmax by approximately 50 %, whereas KD was unaffected. The results provide evidence for at least three different high-affinity [3H]5-HT binding sites, one of them showing a pharmacological profile strikingly similar to that of the mammalian 5-HT1A receptor.

Journal Article↗

PubMed1993

Predator exposure alters brain serotonin metabolism in bicolour damselfish.

The effect of predator exposure on brain serotonin utilization was studied in bicolour damselfish (Pomacentrus partitus). Predator exposure (lasting 2 h), which took place in an aquarium where a transparent wall separated the damselfish from the predator (a graysby, Epinephelus cruentatus), resulted in increased concentrations of 5-hydroxyindoleacetic acid (5-HIAA, the main serotonin metabolite) and 1.6-1.8 fold elevations of 5-HIAA/serotonin ratios (an index of serotonergic activity) in telencephalon, hypothalamus and brain stem. The results show that predator exposure, like intraspecific social stress, induces increased brain serotonergic activity in fish. Different types of stress also elevate brain serotonergic activity in mammals, indicating that this is a phylogenetically very old stress response, possibly helping the animal's coping response.

Animals↗

PubMed1993

Brain sensitivity to anoxia in fish as reflected by changes in extracellular K+ activity.

Most vertebrates have a very limited tolerance to anoxia. The only exceptions to this rule are found among ectothermic species, notably crucian carp (Carassius carassius) and freshwater turtles. It has been assumed that the brains of these species are less sensitive to anoxia than ectothermic brains in general. However, it has not been possible to exclude that anoxia-intolerant species like rainbow trout (Oncorhynchus mykiss) die from heart failure rather than brain failure during anoxia, and that the average ectothermic brain is actually rather insensitive to anoxia. By simultaneously measuring the effect of anoxia on brain extracellular K+ activity ([K+]o), blood pressure, and heart rate in rainbow trout, we show that the rainbow trout brain rapidly loses ion homeostasis during anoxia, despite an initial increase in blood pressure. The rainbow trout brain showed a sudden transient increase in [K+]o (suggesting a rapid depolarization) after approximately 30 min of anoxia at 10 degrees C. At the same time the blood pressure was still close to the normoxic value. In a comparative experiment, crucian carp was found to maintain a low brain [K+]o for at least 6 h of anoxia. Thus the results suggest that the rainbow trout brain is anoxia-intolerant in itself, and that its ability to maintain ion gradients during anoxia is very much lower than that of crucian carp. If temperature differences are taken into account, the anoxia sensitivity of the rainbow trout brain is comparable to that of mammals.

Animals↗

PubMed1993

Changes in the brain levels of GABA and related amino acids in anoxic shore crab (Carcinus maenas).

The effects of anoxia on the brain concentrations of gamma-aminobutyric acid (GABA), glutamate, aspartate, glutamine, alanine, and taurine were measured in the shore crab (Carcinus maenas) and compared with data previously obtained from anoxia-tolerant vertebrates. C. maenas was found to survive 12 h in nitrogen-bubbled water. The changes found in brain amino acid levels were strikingly similar to those seen in anoxia-tolerant vertebrates. Thus, during anoxia, the brain of C. maenas displayed considerable increases in the concentrations of GABA (2.4-fold increase after 12 h) and alanine (8-fold increase after 12 h). By contrast, the brain levels of glutamate, aspartate, and glutamine fell significantly during anoxia, whereas the taurine level remained unchanged. Because GABA is a major inhibitory neurotransmitter in arthropods (as well as in most animal phyla), it is suggested that the increased level of GABA could promote the anoxic metabolic depression displayed by C. maenas and thus prolong anoxic survival. It is also possible that the decreases in glutamate and aspartate levels could play similar roles.

Alanine↗

PubMed1992

Changes in brain serotonergic activity during hierarchic behavior in Arctic charr (Salvelinus alpinus L.) are socially induced.

The experiment was performed in two phases. During the first phase (phase 1) the dominance hierarchy was determined in 4 groups of Arctic charr (Salvelinus alpinus L.), each group consisting of 4 fish. Phase 2 was started by rearranging phase 1 fish into 4 new groups. Group 1 consisted of previously dominant fish and groups 2, 3 and 4 of fish that previously held rank 2, 3 and 4, respectively. After phase 2 telencephalon and brain stem were analyzed with regard to their contents of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), the principle metabolite of 5-HT. No correlation was found between the social rank (measured as dominance index) during phase 1 and the brain serotonergic activity (measured as the ratio 5-HIAA/5-HT) determined after phase 2. However, most important, the 5-HIAA/5-HT ratio was significantly correlated with the last experienced social rank, i.e. that acquired during phase 2. These results shows that the difference in brain serotonergic activity between dominant and subordinate fish develops through social interactions. Further, we found that previous subordinate experience inhibited aggressive behavior, an effect which, in the light of available information on stress and 5-HT, could be related to the increase in brain serotonergic activity. We hypothesize that stress induces an increased serotonergic activity which in turn inhibits the neuronal circuitry which mediates aggressive behavior.

Aggression↗

PubMed1992

The effect of Cu (II) on the electro-olfactogram (EOG) of the Atlantic salmon (Salmo salar L) in artificial freshwater of varying inorganic carbon concentrations.

The effect of inorganic copper species was studied by recording the receptor potential, electro-olfactogram (EOG), from the olfactory epithelium of Atlantic salmon (Salmo salar L). In a series of experiments, the olfactory organ was irrigated with aqueous copper solutions with concentrations of the free cupric ion (Cu2+) ranging from 0.2 to 9.7 microM. The diverse copper species were created by varying the amount of bicarbonate (NaHCO3) in artificial freshwater solutions of equal total copper concentrations. In general, these copper solutions induced a slow depolarization of the baseline followed by a hyperpolarization. The amplitudes of these variations in baseline potentials increased with increasing concentrations of Cu2+ ion, i.e., decreasing concentrations of NaHCO3. Stimulating the olfactory epithelium with L-alanine during the copper exposure evoked atypical EOG responses. The amplitudes and form of the EOGs changed drastically with increasing Cu2+ concentrations, with significant correlation between the reduction in EOG amplitudes and the Cu2+ concentration. The results indicate that among the copper species tested the toxic effect is caused mainly by the dissolved Cu2+ ion. The results also suggest that the Cu2+ ion exerts its toxic effects on the transduction mechanisms of the olfactory receptor cells. The different EOG profiles obtained in response to varying Cu2+ concentrations indicate that this ion affects the transduction mechanisms at different stages.

Animals↗

PubMed1992

Induction of social dominance by L-dopa treatment in Arctic charr.

The effect of L-dopa on social dominance was studied in the juvenile Arctic charr (Salvelinus alpinus). L-dopa is the immediate precursor of dopamine, a neurotransmitter that has been connected with aggressive behaviour in fish as well as mammals. Arctic charr were placed in pairs. One individual in each pair was given L-dopa orally, while the other was given vehicle. The results showed that 18 out of 22 fish given 10 mg L-dopa kg-1 became dominant (p = 0.004, binomial test). A higher dose of L-dopa (200 mg kg-1) induced dyskinesia. L-dopa was found to cause a dose-dependent increase in the brain levels of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC, a major dopamine metabolite), as well as an increase in the DOPAC/dopamine ratio (an index of dopaminergic activity).

Aggression↗

PubMed1990

Differential effects of mercurial compounds on the electroolfactogram (EOG) of salmon (Salmo salar L.).

The effects on the salmon (Salmo salar L.) electroolfactogram (EOG) of the two mercurials, mercuric chloride (HgCl2) and methylmercuric chloride (CH3HgCl), were studied. The EOG responses were evoked by stimulating the olfactory epithelium with 340 microM L-alanine for 10 sec every second minute during a 1-hr period. Each EOG response consisted of an initial peak component followed by a sustained component with an amplitude about 40% below the peak value. Three experimental series, each comprising six fish, were carried out. In the first series, the rosette was irrigated solely with artificial "fresh water." In the two other series, a 5-min exposure to mercury (HgCl2 or CH3HgCl, at 10(-5) M) was included after 10 min and a 15-min exposure after 45 min. The mercuric ion (Hg2+) eliminated the peak response within 2 min and suppressed the sustained response to about 35%. During the subsequent irrigation with mercury-free fresh water, both EOG components regained about 50% of their initial amplitudes. In contrast, methylmercury induced a steady and parallel decline of both the peak and the sustained responses, which were not reversed by rinsing the epithelium with fresh water. The results of this study demonstrate the vulnerability of the olfactory receptor function in fish to mercury exposure. Also, they show the very different effects of inorganic and organic mercurials upon the EOG.

Animals↗