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PubMed2001

Impacts of Oreochromis mossambicus (Perciformes: Cichlidae) upon habitat segregation among cyprinodontids (Cyprinodontiformes) of a species flock in Mexico.

Five species of Cyprinodon in Laguna Chichancanab, Yucatan, Mexico comprise a young species flock whose ecology and evolution has not been thoroughly studied, but whose existence is threatened with extinction. Species flocks evolve in isolated areas where predators and competitors are absent. Since the description of the Chichancanab flock, Oreochromis mossambicus, a species introduced into the lake for which I examined habitat in the 1980's, has become common throughout the basin. I assessed relative abundance of flock species in the lake. examined habitat use and segregation among the three most common flock species and examined the affects of O. mossambicus upon flock species habitat use. Cyprinodon beltrani was the most abundant flock species in 1997, followed by C. maya and C. labiosus; C. verecundus and C. simus were rare. Cyprinodon beltrani was found in shallow water, nearshore, over thick beds of submerged Chara, and little emergent vegetation. Cyprinodon beltrani exhibited diurnal variation in nearshore habitat use. In the field, the habitat use of C. beltrani and O. mossambicus broadly overlapped. In aquarium experiments, three flock species exhibited habitat use segregation and C. beltrani and C. labiosus showed agonistic behaviors that strengthened segregation. Cyprinodon maya differed from C. beltrani and C. labiosus by its greater dispersion of individuals and use of areas higher in the water column. The presence of O. mossambicus caused a shift in habitat use by C. maya and C. labiosus that put these species into habitat occupied by C. beltrani. The presence of introduced species has caused a significant perturbation of the conditions that fomented speciation of the Chichancanab flock 8,000 years ago.

Agonistic Behavior↗
PubMed1986

Prenatal stress increases the behavioral response to serotonin agonists and alters open field behavior in the rat.

Female rats were exposed to mild stress throughout pregnancy and the offspring tested at 60 days of age. In an open field test the prenatal stress group showed increased locomotion and increased rearing compared to control rats confirming that the prenatal stress treatment was sufficient to produce persistent behavioural changes in the offspring. The prenatal stress offspring also showed an increased behavioural response to injections of 5-hydroxy-L-tryptophan (wet-dog shakes) and an enhanced 5-HT syndrome following treatment with the 5-HT agonist 5-methoxy-N,N- dimethyltryptamine. These results provide further evidence that maternal stress produces long-lasting changes in the functioning of central 5-HT neurons in the offspring.

5-Hydroxytryptophan↗
PubMed1998

Effects of fighting after grouping on plasma cortisol concentration and lymphocyte blastogenesis of peripheral blood mononuclear cells induced by mitogens in piglets.

One litter (Group A) of three unacquainted groups of littermates (4 piglets/litter), 64.0 +/- 0.8 days old, was moved to the pen of another litter (Group B) and they were housed together for 19 days after grouping (phase 1). The pigs in Group B violently attacked all the pigs in Group A for 9 hr after grouping. The remaining group was not grouped and used as controls. The plasma cortisol concentrations 1 hr after grouping were significantly higher than those 1 hr before and 24 hr after grouping, and the suppression of lymphocyte blastogenesis of peripheral blood mononuclear cells (PBMC) induced by mitogens was observed on 3, 8 and 19 days after grouping. After phase 1 ended, the pigs in Group A were returned to their own pen for 7 days, and then they were regrouped with the pigs in Group B and reared together for a further 14 days. Neither agonistic behavior nor change of plasma cortisol after regrouping was seen. Though the lymphocyte blastogenesis of PBMC induced by the mitogens on day 0 after regrouping was significantly lower in the pigs of Groups A and B compared to those in control pigs, a significant difference in lymphocyte blastogenesis among three groups was not seen on 7 and 14 days after regrouping. These findings indicate that fighting after grouping unacquainted litters increases plasma cortisol, and suppresses lymphocyte blastogenesis for 26 days after grouping.

Agonistic Behavior↗
PubMed2006

Role of V1a vasopressin receptors in the control of aggression in Syrian hamsters.

The present study investigated the hypothesis that social isolation increases aggression by increasing the number of V1a vasopressin receptors in the anterior hypothalamus (AH). Male hamsters were randomly assigned to a group that was allowed to interact with a small nonaggressive hamster three times each week for 3 weeks (socially experienced) or to a group that did not interact socially with other hamsters (social isolates). On the final day of the experiment, hamsters in both groups were placed in a neutral arena with a small, nonaggressive intruder, and agonistic behavior was scored for 10 min. In social isolates, the duration of aggression and the number of attacks were significantly greater than in socially experienced hamsters. There were no significant between-group differences in the latency to the onset of aggression, the number of flank marks or in the duration of defensive/submissive, social or nonsocial behavior. The amount of V1a receptor binding was significantly greater in the AH, the paraventricular nucleus of the hypothalamus and the lateral hypothalamus in the social isolates than in the socially experienced hamsters. The amount of V1a receptor binding was significantly greater in the central amygdala of socially experienced hamsters than in socially isolated hamsters. Serum concentrations of testosterone were significantly higher in the socially experienced hamsters than in social isolates. These data support the hypothesis that social isolation increases aggression by increasing the number of V1a vasopressin receptors in the AH.

Aggression↗
PubMed1978

Differential aggression in genetically different morphs of the white-throated sparros (Zonotrichia albicollis).

To see if genetic differences correlate with differences in agonistic behavior, 225 encounters within and between color morphs of the white-throated sparrow (Zonotrichia albicollis) were observed in feeding groups of different sizes and morphic compositions. Tan morphs lack the M chromosome that replaces either of two chromosomes in the white morph. The data were analysed using quantitative models accounting for the proportions of morphs present, and the principal finding was that morphs are equally frequent recipients of aggression but the white morph was the aggressor more frequently than by chance expectation--regardless of the morph of the recipient, the size of the group or the morphic composition of the group.

Aggression↗
PubMed1983

Genetic factors in drug neuroteratogenicity.

The exposure in humans to ethanol or barbiturates during prenatal or neonatal development is common. There are indications that the magnitude of the resulting symptoms may be genetically determined. In the present article, an animal model was established for the study of the genetic determination of the neurosensitivity to ethanol and barbiturates administered during prenatal and/or neonatal development. Inbred C57BL/10 (C57) and DBA/1 (DBA) mice were employed in the ethanol studies and these strains and the outbred HS/Ibg (HS) were used in the barbiturate studies. Early ethanol administration induced a long lasting increase in the susceptibility to audiogenic seizures in both strains but to a greater degree in C57. Neuropharmacological studies implicated the serotonergic but not the noradrenergic system as mediating the early ethanol induced changes in audiogenic seizures. Open field activity was decreased but only in C57. Male agonistic behavior and predatory behavior were greatly reduced by early ethanol administration but mainly in DBA. Long term induction of the activity of the hepatic enzymes, alcohol dehydrogenase and microsomal ethanol oxidizing system, occurred in both strains after early exposure to ethanol. After early exposure to phenobarbital HS mice had long lasting increases in the susceptibility to audiogenic seizures and in the hippocampus related behaviors, spontaneous alternations and eight arm maze performance. The hepatic microsomal drug oxidizing system was induced in adult HS mice with early phenobarbital (PhB) exposure. Early PhB exposure also caused long term decreased sensitivity to ethanol narcosis and an accelerated acquisition to barbiturate tolerance, possibly mediated via a change in the sensitivity of the post synaptic dopamine receptors. Changes in the PhB treated offspring also included a reduction in the levels thyroid hormone. Early exposure to PhB resulted in a long term deficit in the area of brain layers, number of neurons, dendritic spines and the ultrastructure. Strain comparison suggested that DBA was less neurosensitive to early PhB administration than both HS and C57. It was concluded that genotype-environment interaction exists in the effect of drugs on the developing CNS.

Acoustic Stimulation↗
PubMed2001

Long-term effects of social stress on antiviral immunity in pigs.

Mixing of unfamiliar pigs is common practice in intensive pig husbandry. Since pigs maintain a dominance hierarchy, mixing often leads to vigorous fighting. Apart from the negative impact that fighting has on welfare, there is evidence that the social stress associated with fighting suppresses immune function. In the present experiment, we investigated the impact of mixing on specific long-term immune responses and protection against challenge infection after vaccination with pseudorabies virus (PRV). Specific pathogen-free (SPF) pigs were mixed pairwise with an unfamiliar same-gender conspecific or left undisturbed with a same-gender littermate at 3 days after vaccination with PRV. Half of the pigs were females (gilts) and half were castrated males (barrows). Mixing increased agonistic behavior to the same degree in gilts and barrows. Cortisol concentrations in saliva and catecholamine excretion in urine were increased in mixed pigs, and these effects were independent of dominance status and gender. Subsequently, the effects of mixing, gender, dominance status and interactions between these factors on immune response parameters were studied. The main result was that mixed barrows showed suppressed immune responses after vaccination and increased clinical symptoms after challenge infection compared to control barrows. Mixed gilts however did not differ from control gilts. It also appeared that mixed dominants were more seriously affected than mixed subordinates were. We conclude that, in some pigs, social stress after mixing suppresses the immune response to a viral vaccine and consequently impairs protection against challenge infection.

Agonistic Behavior↗
PubMed2004

Reduced aggression in AMPA-type glutamate receptor GluR-A subunit-deficient mice.

The importance of AMPA-type glutamate receptors has been demonstrated in neuronal plasticity and in adaptation to drugs of abuse. We studied the involvement of AMPA receptors in social interaction and anxiety and found that in several paradigms of agonistic behavior naïve male mice deficient for the GluR-A subunit- containing AMPA receptors are less aggressive than wild-type littermates. GluR-A deficient mice and wild-type littermates exhibited similar basic behavior and reflexes as monitored by observational Irwin's test, but they tended to be less anxious in elevated plus-maze and light-dark tests. Maternal aggression or male-female encounters were not affected which suggests that male hormones are involved in the expression of suppressed aggressiveness. However, testosterone levels and brain monoamines can be excluded and found to be similar between GluR-A deficient and wild-type littermates. The reduced AMPA receptor levels caused by the lack of the GluR-A subunit, and measured by a 30% reduction in hippocampal [3H]-S-AMPA binding, seem to be the reason for suppressed male aggressiveness. When we analyzed mice with reduced number of functional AMPA receptors mediated by the genomic introduced GluR-A(Q582R) channel mutation, we observed again male-specific suppressed aggression, providing additional evidence for GluR-A subunit-containing AMPA receptor involvement in aggression.

Agonistic Behavior↗
PubMed2000

Pituitary-adrenocortical responses to the first dyadic encounters in male rhesus monkeys: effect of dominance relationship.

Male rhesus monkeys unfamiliar with each other were paired in a cage, and blood samples were collected before and a few hours after pair formation. Adrenocorticotrophic hormone (ACTH) and cortisol levels in each blood sample were measured. Dominant-subordinate status was ascertained through two rank tests, the food competition test and the agonistic behavior test, which were performed immediately after pair formation. As a result, the dominance relationship was determined in seven pairs formed from five animals, and the differences in ACTH and cortisol values between the dominant and subordinate animal in these pairs were compared statistically. The day after the first encounter, a second encounter was conducted in randomly selected pairs of monkeys. In the first encounters, higher levels of both ACTH and cortisol were detected in dominant animals in comparison to subordinate animals. Changing the animal's partner altered the stress responses whenever the animal's dominant-subordinate status changed. The elevated levels of ACTH and cortisol in dominant animals disappeared on the day after the first encounter. In dominant animals, the pituitary-adrenocortical stress response reacts sharply to situational demands, whereas subordinate animals have a weaker response. This acute stress response is different from a chronic stress response. When the subordinate animal cannot escape, its hypothalamic-pituitary-adrenocortical axis appears to be suppressed.

Adrenocorticotropic Hormone↗
PubMed1995

On the agonistic display of the Siamese fighting fish. I. The frontal display apparatus.

The agonistic behavior of the Siamese fighting fish has long been a popular subject for ethologists. While this behavior is well documented, its physiological basis is still poorly understood. One of the most important components of this behavior is the frontal display, in which a fish faces its opponent directly with tonically extended gill covers. As a first step towards establishing this display as a model for behavioral physiology, the musculoskeletal structure of the frontal display apparatus is examined. The opercular bones and the opercular abductor, the opercular dilator muscle, appear to have undergone adaptive modifications that facilitate the display. The opercular bone rotates around the hyomandibular bone through a ball-and-socket joint. Due partly to a reduction of its articulation with the preopercular bone, the operculum can rotate as much as 90 degrees around this joint. The opercular dilator muscle consists of three parts: a deep belly--DO alpha, and two superficial bellies--DO beta and DO gamma. The three portions have different origins, but all three insert on the lateral surface of the opercular bone just dorsal to the spheroidal joint. In comparison, the opercular dilator muscle of the sunfish and the goldfish lacks the superficial bellies. Innervation of this muscle is derived from the maxillary division of the trigeminal nerve, all three portions are innervated by axons from the same fascicle, suggesting that they are embryologically related. The superficial bellies consist of uniform, large muscle fibers. The deep belly consists of an external group of large fibers around a central tendon, and an internal group of small fibers. Enzyme histochemistry shows that the external group of fibers consists mostly of fast-twitch fibers, whereas the internal group consists of slow, oxidative fibers. Direct stimulation demonstrates that all bellies can mediate opercular extension. The architectural and biochemical differences among the three portions suggest that they are functionally not equivalent. The fast-fatiguing muscles may mediate the initiation, while the large fibers of the superficial bellies and the small oxidative fibers of the deep belly may be involved in the maintenance of the display.

Agonistic Behavior↗
PubMed2002

2,5'-Disubstituted adenosine derivatives: evaluation of selectivity and efficacy for the adenosine A(1), A(2A), and A(3) receptor.

Novel 2,5'-disubstituted adenosine derivatives were synthesized in good overall yields starting from commercially available guanosine. Binding affinities were determined for rat adenosine A(1) and A(2A) receptors and human A(3) receptors. E(max) values were determined for the stimulation or inhibition of cAMP production in CHO cells expressing human adenosine A(2A) (EC(50) values as well) or A(3) receptors, respectively. The compounds displayed affinities in the nanomolar range for both the adenosine A(2A) and A(3) receptor, without substantial preference for either receptor. The derivatives with a 2-(1-hexynyl) group had the highest affinities for both receptors; compound 4 (2-(1-hexynyl)adenosine) had the highest affinity for the adenosine A(2A) receptor with a K(i) value of 6 nM (A(3)/A(2A) selectivity ratio of approximately 3), whereas compound 37 (2-(1-hexynyl)-5'-S-methyl-5'-thioadenosine) had the highest affinity for the adenosine A(3) receptor with a K(i) value of 15 nM (A(2A)/A(3) selectivity ratio of 4). In general, compounds with a relatively small 5'-S-alkyl-5'-thio substituent (methyl-5'-thio) displayed the highest affinities for both the adenosine A(2A) and A(3) receptor; the larger ones (n- or i-propyl-5'-thio) increased the selectivity for the adenosine A(3) receptor. The novel compounds were also evaluated in cAMP assays for their (partial) agonistic behavior. Overall, the disubstituted derivatives behaved as partial agonists for both the adenosine A(2A) and A(3) receptor. The compounds showed somewhat higher intrinsic activities on the adenosine A(2A) receptor than on the A(3) receptor. Compounds 37, 40 and 45, 48, with either a 5'-S-methyl-5'-thio or a 5'-S-i-propyl-5'-thio substituent had the lowest intrinsic activities on the adenosine A(2A) receptor. For the A(3) receptor, compounds 34, 35, 38, 39, and 46, 47, with a 5'-S-ethyl-5'-thio or a 5'-S-n-propyl-5'-thio substituent had the lowest intrinsic activities.

Adenosine↗
PubMed2003

Differential activation of dual signaling responses by human H1 and H2 histamine receptors.

Stimulation of human H1 and H2-histamine receptors (HRs) primarily activates signaling pathways to increase intracellular calcium [Ca2+]i and cyclic AMP (cAMP), respectively. Activation of H2-HR in human embryonic kidney (HEK) cells by histamine and dimaprit increases both cAMP formation and [Ca2+]i, as determined by cAMP-scintillation proximity assays and fluorescence imaging plate reader (FLIPR) assays. In HEK cells expressing relatively high levels of H2-HR (Bmax=26 pmol/mg protein), histamine and dimaprit are full agonists in eliciting cAMP responses with pEC50 values of 9.30 and 7.72 that are 1000-fold more potent than their respective pEC50 values of 6.13 and 4.91 for increasing [Ca2+]i. The agonist potencies decrease for both responses at lower H2-HR density (5 pmol/mg protein) and dimaprit exhibits partial agonist behavior for the [Ca2+]i response. The inverse agonists ranitidine and cimetidine more potently inhibit cAMP production in the higher expressing H2-HR line. Histamine also activated both signaling pathways via human H1-HRs highly expressed (Bmax=17 pmol/mg protein) in HEK cells, with a 1000-fold greater potency for [Ca2+]i vs. cAMP responses (pEC50=7.86 and 4.82, respectively). These studies demonstrate a markedly different potency for activation of multiple signaling pathways by H1- and H2-HRs that may contribute to the selectivity of histamine responses in vivo.

Calcium Signaling↗
PubMed2003

Comparative psychology of surprising nonreward.

The surprising or unexpected omission of an appetitive reinforcer has at least two effects: An allocentric effect according to which the organism updates knowledge about the environment, and an egocentric effect that allows the organism to learn about its own emotional reaction to the change. This egocentric effect (traditionally called frustration) is correlated to activation of the hypothalamic-pituitary-adrenal axis, can be modulated by treatment with anxiolytics, and is expressed in terms of behavioral changes that have an emotional component (e.g., agonistic behavior). It is hypothesized that all vertebrates share the mechanisms underlying the allocentric effect, but only mammals possess the mechanisms underlying the egocentric effect. It is further argued that frustrative mechanisms evolved in early mammals from those underlying fear conditioning.

Amphibians↗
PubMed1994

Effects of 5-HT3 agonists on reproductive behaviors in rats.

Activity at 5-HT1 and 5-HT2 receptor sites influences sexual behavior in male and female rats. 5-HT3 antagonists reportedly have no effect on copulatory activity in rats of either sex although they influence a variety of other behaviors. The effects of 5-HT3 agonists on sexual behavior are unknown. The following experiments were undertaken to assess the influence of the 5-HT3 agonists 1-phenylbiguanide (PBG) and 2-methyl-serotonin (2-Me-5-HT) on sexual behavior, when administered intracerebroventricularly. Consistent with earlier reports indicating that 5-HT1 and 5-HT2 receptor activity influences reproductive activity in a sex-dependent manner, PBG was found to facilitate male, but not female, rat sexual behavior. 2-Me-5-HT, however, failed to modify either female or male rat sexual activity. Evidence that PBG, but not 2-Me-5-HT, induces carrier-mediated dopamine release suggests that the effect of PBG in male rats is due to dopaminergic mediation. Overall, the present data indicate that 5-HT3 receptor activation has only slight effects on rat sexual behavior.

Animals↗
PubMed1980

Differential behavioral and biochemical effects of four dopaminergic agonists.

Some behavioral and biochemical effects of four dopaminergic agonists (apomorphine, piribedil, lergotrile, and bromocriptine) were determined in the mouse. As expected, all four drugs dose-dependently reversed the alpha-methyltyrosine-induced decline of forebrain dopamine. All four compounds reduced locomotor activity at low doses, but only apomorphine and bromocriptine increased motor activity at higher doses. All four drugs caused some reversal of the baclofen-induced elevation in forebrain dopamine concentrations, but only apomorphine and bromocriptine completely reversed the effects of baclofen. After chronic treatment with haloperidol, the behavioral effects of lergotrile and bromocriptine were altered. Doses of those drugs reducing motor activity in normal animals were ineffective after chronic haloperidol. The latent stimulation induced by bromocriptine was enhanced, while a stimulatory effect of lergotrile emerged in these animals. These effects were noted in conjunction with an enhanced sensitivity to the drug-induced decrease in dopamine turnover. These results demonstrate that dopamine agonists may be differentiated on the basis of certain behavioral and biochemical tests and suggest an interaction of these drugs with two different populations of dopamine receptors.

Animals↗
PubMed1991

Chronic levodopa impairs the recovery of dopamine agonist-induced rotational behavior following neural grafting.

The effect of chronic levodopa treatment on the function of embryonic mesencephalic tissue grafts was assessed in rats by monitoring rotational behavior elicited by dopamine (DA) agonists before and after neural grafting. Rats were given unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway and baseline measures of rotational behavior induced by D1 receptor stimulation, D2 receptor stimulation, or amphetamine were determined. Subsequently, DA grafts were implanted into the lesioned striatum and chronic regimens of either saline or levodopa began one day after neural grafting and were continued for 7 weeks. Rotational behavior elicited by the D1 agonist, SKF 38393, was completely attenuated throughout the six-week-period following the commencement of levodopa treatment, regardless of the absence or presence of a DA graft. Conversely, rotational behavior elicited by the D2 agonist, quinpirole, was significantly elevated in ungrafted animals receiving chronic levodopa. Grafted animals receiving chronic levodopa did not show a significant reduction in rotational behavior, whereas grafted animals receiving chronic saline showed a significant 67% reduction in quinpirole-induced rotational behavior. Amphetamine-induced rotational behavior was reduced in both levodopa and saline treated grafted animals, however grafted animals receiving chronic levodopa treatment showed a reduction of rotational behavior that was uncharacteristic and less compensatory than that observed in grafted animals receiving chronic saline treatment. Morphology of grafts indicate that there were areas of impaired neurite outgrowth of TH-positive fibers in animals treated with levodopa. The results of the present study suggest that the impaired recovery in quinpirole- and amphetamine-induced rotational behavior in grafted animals receiving chronic levodopa treatment may be related to (1) impaired graft function, (2) an alteration in pre- and postsynaptic mechanisms in the host DAergic system, or (3) a combined effect of (1) and (2).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1986

Effects of ovariectomy, social instability and social status on female Macaca fascicularis social behavior.

The effects of ovariectomy, social instability and social status on affiliative and agonistic behavior were studied in 44 females housed in 10 unimale groups. Five of the groups contained ovariectomized females and five groups contained intact females. The membership among three groups of intact females (n = 13) and three groups of ovariectomized females (n = 13) was reorganized every three months (unstable), and the other groups were left undisturbed (stable) for the 22 month study. The behavior of each female was recorded during 160 (stable) or 190 (unstable) 15 min focal observations of each subject. The social status of each female was determined by outcomes of agonistic interactions. It was hypothesized that the effects of social instability and status would be more pervasive than the effects of ovariectomy. It was found that ovariectomy reduced interfemale affiliation and increased male-female agonism. Social instability increased submissions to males and females and time spent alone, and decreased interfemale affiliation. Dominant animals were more aggressive and less submissive than subordinates. Thus, ovariectomy influenced both isosexual and heterosexual social interaction, implying mediation of these behaviors, at least in part, by ovarian hormones.

Animals↗
PubMed1993

Ethanol-induced enhancement of defensive behavior in different models of murine aggression.

The effects of alcohol on agonistic behavior in mice were studied by introducing an intruder mouse to a resident, alcohol-treated test animal (or saline-injected control). Alcohol (0.1-2.0 g/kg, IP) was administered 20 minutes before testing, and an ethological analysis was made of all behavioral elements shown by the treated animal during a 500-second period. Alcohol did not increase aggression, whether baselines were high, low or experimentally suppressed. Defensive activities, however, were dose-dependently increased, with a threshold dose of 0.5 g/kg or lower in some situations. This suggests that alcohol did not reduce "anxiety" or "fear." Aggression tended to decrease, even with doses as low as 0.5 g/kg, which produced BACs of only 25-40 mg/dl at the start of the testing period. With the highest dose, however, aspects of timidity were still increased after 3 hours, but aggression returned to control level after 1 hour, when the BAC was about 250 mg/dl. In other studies, increased aggression has generally been found only with low alcohol doses. This acute tolerance to the anti-aggressive effect of alcohol reported here suggests the possibility of finding pro-aggressive effects at much higher BACs, perhaps more closely simulating the human situation.

Aggression↗