Ethologic analysis of the action of enkephalins on intraspecific behavior

Abstract

612.821.i/.3.014.46:547.95:547.943 and M. I. Titov KEY WORDS: aggression; defense; intraspecific behavior; met-enkephalin; leu-enkephalin.The role of enkephalins and their analogs in the regulation of mechanisms of memory, analgesia, certain motor acts, and autonomic reactions has been demonstrated recently [4,[6][7][8]. However, the spectra of their action on intraspecific (zoosocial) behavior have not been analyzed.The aim of the present investigation was to analyze the spectrum of action of met-and leu-enkephalins and of the tetrapeptide Tyr-D-AIa-GIy-Phe-NH2 on various forms of intraspecific behavior of isolated aggressive mice and to compare it with the analgesic activity of these peptides.Identification and analysis of effects of this sort are important in order to understand the role of endogenous peptides and their synthetic analogs in the regulation of complex forms of behavior. EXPERIMENTAL METHODExperiments were carried out on 30 male CC57W mice kept in single cages for 12 weeks. Free interaction of an aggressive isolant with a standard partner from the group was recorded by means of a special combination of Ethograph and EC 1022 computer [3]. The frequency and order of appearance of 25 different behavioral acts and postures of the isolated animal were recorded.All acts and postures were classified in motivation categories and coded on a binary code for computer analysis.The behavioral acts were subdivided into categories characterizing zoosocial behavior (intraspecific sociality), aggression, ambivalent (double motivational) behavior, defense, and individual behavior ( Table I). The degree of analgesia was estimated in points on the basis of behavioral criteria [i, 2]. Met-and leu-enkephalins and the tetrapeptide were injected intraperitoneally in a volume of 0.i ml/10 g body weight.Metenkephalin also was injected into the lateral ventricle in doses of 50 ~g. The effects were assessed 5 and 30 min after injection of the preparations.The significance of the results was estimated by means of Wilcoxon's nonparametric criterion for conjugate sets. EXPERIMENTAL RESULTSMet-enkephalin in a dose of 50 mg/kg increased the likelihood of an aggressive attack on the partner 5 min after systemic injection (Table i), reduced intraspecific sociality, potentiated ambivalent forms of behavior, and reduced the likelihood of individual forms of behavioroIn the above-mentioned doses, met-enkephalin did not cause analgesia, as assessed by behavioral criteria (n = 6, T A = O; P <0~ ~fter 30 min the frequency of overt aggressive acts was close to the control values, but threatening manifestations were increased, as also was vertical motor activity (standing up on the hind limbs).Leu-enkephalin, in a dose of 50 mg/kg, reduced intraspecific sociality after 5 min (Table I) and potentiated aggressive behavior.Unlike met-enkephalin, leu-enkephalin induced defensive behavior in the mice, which was not observed in the control.Leu-enkephalin depressed dynamic and intensified static (sitting) forms of individual behavior.After 3...

Ethological analysis of neuropeptides and psychotropic drugs: Effects on intraspecies aggression and sociability of isolated mice

“…They are involved in memory mechanisms [Sandman and Kastin, 19771, analgesia [Kosterlitz and Hughes, 19751, and individual and social behavior [Poshivalov et al, 1982;Valdman et al, 19801. They can simultaneously function as neuromediators, neuromodulators, and neurohormones.…”

“…It has been reported that endogenous neuropeptides and their synthetic analogs have a wide spectrum of neurotropic effects [De Wied, 1973;Kastin et al, 1979bl. They are involved in memory mechanisms [Sandman and Kastin, 19771, analgesia [Kosterlitz and Hughes, 19751, and individual and social behavior [Poshivalov et al, 1982;Valdman et al, 19801. They can simultaneously function as neuromediators, neuromodulators, and neurohor-mones.…”