The effect of raising or lowering tryptophan levels on aggression in vervet monkeys
| Autor: | Simon N. Young, Brian Chamberlain, Frank R. Ervin, Robert O. Pihl |
|---|---|
| Rok vydání: | 1987 |
| Předmět: |
Male
medicine.medical_specialty Clinical Biochemistry Central nervous system Motor Activity Toxicology Biochemistry Behavioral Neuroscience chemistry.chemical_compound Sexual Behavior Animal Sex Factors Internal medicine Chlorocebus aethiops medicine Animals Neurotransmitter Social Behavior Biological Psychiatry 5-HT receptor Pharmacology CATS Aggression Tryptophan Grooming Diet Endocrinology medicine.anatomical_structure chemistry Hypothalamus Female Serotonin medicine.symptom Psychology |
| Zdroj: | Pharmacology, biochemistry, and behavior. 28(4) |
| ISSN: | 0091-3057 |
| Popis: | were given amino acid mixtures that were tryptophan-free (T-), nutritionally balanced (B), or contained excess tryptophan (T+). The T- mixture caused a marked decrease in plasma tryptophan and the T+ mixture a large increase. Behavioral observations were made on the animals after administration of the amino acid mixtures both during spontaneous activity and while the (fasted) animals were competing for food newly placed in the feeder. The only effect of the biochemical manipulations on spontaneous aggression was an increase in aggression of the male animals with the T- mixture. During competition for the food the T- mixture increased and the T+ mixture decreased aggression in the males, while the T+ mixture decreased aggression in females. These data indicate that brain 5-hydroxytryptamine can influence aggression in a primate and suggest that altered tryptophan levels can influence aggression more reliably at higher levels of arousal. Vervet monkeys Aggression Tryptophan 5-Hydroxytryptamine THE neuroanatomical pathways of the brain that are served by the neurotransmitter 5-hydroxytryptamine (5HT) have been shown to play an important inhibitory role for a number of behavioral states including arousal, sensitivity to pain, sexual behavior, activity levels, sensitization and habitua- tion to novel stimuli, irritability and aggression [29,45]. The relationship between 5HT function and aggression has been the focus of a particularly large number of studies many of which have employed parachlorophenylalanine (PCPA) as a means of depleting 5HT. PCPA is a relatively specific inhibitor of 5HT synthesis [22]. Thus, PCPA has been shown to increase irritability [22], to facilitate muricide in rats [13, 30, 34, 38] and cats [8], filicide (pup killing) in rats [6], and grillicide (cricket-killing) in mice [23]. These effects may be partially or completely reversed by administration of the 5HT precursor 5-hydroxytryptophan [6, 8, 13, 30, 34, 38] or fiuoxetine, a selective inhibitor of 5HT uptake into presynaptic terminals [1]. Also, PCPA has been reported to potentiate brain stimulated (ventromedial hypothalamus) af- fective attack in cats [21], isolation-induced aggression [28] or territorial aggression [39] in mice, shock elicited aggres- sion in rats [37,41], and spontaneous aggression in monkeys [36]. Although reports of no effect or of a decrease in ag- gression following PCPA treatment have also been made [5, 24, 25], for the shock-elicited aggression paradigm at least, the inconsistency seems to be due to differences in choice of test parameters between studies [41]. Depletion of brain 5HT by means of electrolytic lesions of midbrain raphe nuclei [17, 46, 49, 50] or administration of the selective 5HT neurotoxins 5,6-dihydroxytryptamine (DHT) and 5,7-DHT [3, 16, 19] also facilitates aggression in various animal models. Again these effects may be reversed by ad- ministration of the 5HT precursors tryptophan or 5- hydroxytryptophan [19,50]. Conversely, treatment with drugs that are belived to increase 5HT neurotransmission [15, 27, 32, 40] has been shown to decrease aggressivity. A non-pharmacological approach to the study of the rela- tionship between 5HT and aggression has been the use of tryptophan-free diets to lower brain 5HT. Because the syn- thesis of 5HT depends on tryptophan availability [48], limit- ing dietary tryptophan leads to depletion of brain 5HT levels [2, 11, 14]. Feeding rats a tryptophan-free diet for 4 to 6 days has been reported to induce mouse killing in non-killer rats and to decrease attack latencies of killer rats [14]. The diet reduced brain 5-hydroxyindole levels by about 30% whereas supplementation of this diet with tryptophan reversed the effect on both aggression and brain 5HT. Another study [20] confirmed the finding that a tryptophan-free diet increases 1Requests for reprints should be addressed to Dr. S. N. Young, Department of Psychiatry, McGill University, 1033 Pine Avenue West, Montreal, Canada H3A 1A1. 503 |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|