Biomedical subjects

B M Spruijt

Publications and source records attributed to B M Spruijt.

81 records · Page 5Linked to original sources

PubMedDate not supplied

Comparison of structural requirements of alpha-MSH and ACTH for inducing excessive grooming and pigment dispersion.

alpha-MSH and ACTH-like peptides are known to play an important role in the adaptation of many vertebrates to a new environment. These peptides induce pigment dispersion in amphibian melanophores through a receptor-mediated mechanism. In this study we compared the structural requirements of these peptides for melanotropic activity on Xenopus laevis melanophores with those for inducing excessive grooming in the rat. With the exception of ACTH1-24 there is a close resemblance in structure-activity relationships of the fragments and analogs tested in the two bioassays. [Nle4,-D-Phe7]-alpha-MSH is extremely active in both assays. Weak agonists such as [Leu9]-alpha-MSH did not possess antagonistic properties either in the melanophore assay or in the excessive grooming test. The data suggest that the mechanism of action of alpha-MSH-like peptides in rat brain is receptor-mediated like their action on melanophores.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

ACTH1-4 potentiates alpha-MSH-induced melanophore dispersion and excessive grooming.

The biological activity and a possible modulatory role of the N-terminal tetrapeptide Ser-Tyr-Ser-Met from alpha-MSH/ACTH was tested in the Anolis melanophore assay, the Xenopus melanophore assay, tyrosinase stimulation in mouse melanoma cells and in excessive grooming in the rat. ACTH1-4 did not exhibit biological activity in any of these four assays nor did it have modulatory properties in the Xenopus and the melanoma cell assay. However, in the Anolis assay ACTH1-4 potentiated pigment dispersion induced by alpha-MSH, alpha-MSH5-13 and ACTH1-24 by a factor of about 2. In the grooming assay ACTH1-4 potentiated the effects of alpha-MSH, alpha-MSH5-13, ACTH1-16 and ACTH5-16, but not those of ACTH1-24. Oxidized ACTH1-4 was without biological activity and potentiating properties in all four assays. This study shows that small fragments of the pro-opiomelanocortin precursor, which are devoid of biological activity, can modulate peripheral and central actions of alpha-MSH/ACTH.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

The ACTH/MSH (4-9) analog Org2766 improves retrieval of information after a fimbria fornix transection.

The fimbria fornix of male Wistar rats was transected unilaterally after they had been successfully trained in the Morris maze and the passive avoidance task. Sham-operated and lesioned animals were treated either with Org2766 or saline for two weeks. Subsequently, the performance of all groups was tested again starting two days after the last treatment. The lesioned animals showed a deficit in performance in both tasks, indicating interference of the lesion with retrieval of information. Org2766 improved the poor performance of the lesioned animals in the Morris maze, but not in the passive avoidance task.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

The MSH/ACTH(4-9) analog Org2766 counteracts isolation-induced enhanced social behavior via the amygdala.

MSH/ACTH-like peptides influence social behavior induced by isolation It has been previously demonstrated that changes in locomotor activity as a result of isolation can be counteracted by Org2766 via the amygdala. The present study investigates whether isolation-induced changes in social behavior can also be affected by this peptide via the amygdala. A fully automated observation system was applied for detailed registration and analysis of movements of group-housed and 7-day isolated rats in a social interaction test. Administration of the MSH/ACTH(4-9) analog into the central nucleus of the amygdala elicited decreased locomotion, approach, and avoidance behaviors after isolation as compared to placebo-treated controls. However, general activity and social interest of group-housed rats were not affected by the MSH/ACTH(4-9) fragment. It is hypothesized that the amygdala is a site of action for neuropeptides in modulating social behavior.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Behavioral changes in ACTH-(1-24)-induced excessive grooming in aging rats.

Age-related behavioral changes are commonly associated with impaired cognitive functioning. As a result an abundance of neuropsychological tools have been developed to study learning and memory in man and animal. The combined use of ethological methods and the extensively studied measures of excessive grooming behavior in rats provides an excellent tool to study non-cognitive behavioral changes. In the present study, a sequential analysis was applied to the different grooming elements. Aged rats showed a loss in the sequential organization of their grooming behavior, which led to a decrease in the display of tail sniffing. Interestingly, the reduced display of an element which appears latest in the ontogeny of grooming is reminiscent of the Jacksonian principle of behavioral degeneration. Seemingly, this principle is not necessarily confined to learning paradigms, but may be extended to other behavioral systems as well.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Progressive decline in social attention in aging rats: an information-statistical method.

The purpose of this study was to assess the earliest signs of behavioral changes during aging. In a longitudinal setup the spontaneously displayed social behavior was observed and analyzed. Social interactions offer an appropriate paradigm for studying a gradual decrease in several categories of social behavior in aging animals. The frequencies and durations of 12 behavioral categories collected over 18 sessions yield a wealth of data, which is difficult to evaluate. Therefore, an information-statistical analysis was used, which compressed the frequencies and sequential organization of behavior into a very sensitive and meaningful index. This index expressing the predictability of behavior does not only show age-related changes but also yields an interpretation of the complex changes seen in frequency distributions. The applied analysis focuses on the predictability of behavior, which may be predominantly determined by the animal's own preceding behavior or by the behavior of its social partner. It is shown that the influence of the behavior of a partner on ongoing behavior declines age-dependently, whereas the influence of the animal's own preceding behavior increases. The simultaneous change in these two indices is interpreted as a progressive decline in social attention, which seems to be characteristic for aging rats. It is concluded that the analysis of the sequential organization of behavior offers a new tool, useful in longitudinal behavioral studies on aging.

Aging↗

PubMedDate not supplied

An ACTH4-9 analog enhances social attention in aging rats: a longitudinal study.

Effect of chronic treatment of the ACTH4-9 analog, Org2766, on social attention was studied longitudinally in aging rats. A 6-week treatment temporarily enhanced specific combinations of behaviors of two interacting animals. During a 6-month treatment social attention of treated animals remained at the same level, whereas control animals showed a gradual decrease. Two months after the treatment was ceased this effect on social attention was still present; moreover, the peptide-treated animals performed better in a spatial water maze task three months after the last injection. In addition, the nerve conduction velocity of the major caudal nerves and the sciatic nerve were measured; aged, peptide-treated animals preserved their conduction velocity. The present study shows beneficial long-lasting effects of the ACTH4-9 analog in aging rats on complex behavioral indices and on a physiological measure.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Increased rigidity with age in social behavior of Java-monkeys (Macaca fascicularis).

In this study we investigated the effect of aging on the structure of behavior of socially housed Java-monkeys. Indices of the sequential structure of an animal's own ongoing behavior and of its responses to behavior of other animals were calculated using an information statistic approach. These indices reflect information-processing abilities of an animal, as they represent the ability of an animal to adjust its behavior in response to actions by interaction partners. The influence of an animal's dominance history on the age-related changes was investigated as well. In the literature social subordinance in monkeys is generally associated with elevated levels of cortisol which, in turn, have been suggested to influence information processing abilities. In this study, old animals of low dominance history became more rigid in their own ongoing behavior, whereas old animals of high dominance history did not differ from young animals. The ability of old animals to maintain normal levels of predictability during social interactions declined, but only in social interactions with unfamiliar animals, such as young or unrelated animals. These results may explain the generally found social withdrawal of old non-human primates.

Aging↗

PubMedDate not supplied

Aging, dominance history, and social behavior in Java-monkeys (Macaca fascicularis).

The aim of this study was to investigate the influence of the dominance history of socially housed Java-monkeys on the aging process. In monkeys, social subordinance is generally associated with elevated levels of cortisol, which, in turn, have been suggested to influence cognitive decline. As cognitive skills are necessary for successful social life, we investigated the effect of old age in relation to the dominance history of the animals on their social behavior by comparing old females with their younger daughters. Old age, especially in combination with a history of low rank, led to a withdrawal from social interactions with unfamiliar animals and to a decrease in amounts of aggression received. Still, however, old animals showed an increase in behaviors associated with arousal. A reduced ability to deal with complex social interactions, caused by a decline in information processing abilities, is suggested as an explanation for these results.

Aggression↗