Brain Tryptophan in Isolated Aggressive Mice

Abstract

Circadian variations in whole brain tryptophan level and food intake were investigated in both normally grouped and isolated male Albino-Swiss mice, maintained on a 12:12 light-dark regimen (lights on 08.00–20.00). A significant diumal rhythm in brain tryptophan level was evidenced only by grouped animals, in contrast to the relatively sustained and significantly lower tryptophan level found to exist in isolated mice. Significant, daily rhythms in food intake, for both isolated and grouped mice were found to exist, that were highly correlated in phase. Isolated mice, however, consistently demonstrated an increased food consumption throughout the 24-hour period. These results suggest that a possible alteration in tryptophan metabolism exists in isolated mice, as tryptophan, an essential amino acid, is obtained by mammals only through their diet.

Effect of <i>p</i>-Chlorophenylalanine on Avoidance Learning of Two Differentially Housed Mouse Strains

“…1976). The decreased 5-HT turnover correlates well with recent evidence that isolated animals have a lower level of brain tryptophan (TP) (Miller et al, 1979;Pack ter et aL, 1978). Further, in isolated animals PCPA as well as midbrain raphe lesion greatly improve the learning of an active avoidance task, while the same behavioral performance is impaired by PCPA or improved to a lesser extent by mid brain raphe lesion in normally grouped mice (Valzelli, 1973b;Valzelli et al, 1976).…”

“…The dose of 100 mg/kg of PCPA, behaviorally studied on avoidance learning of differntially housed mice of both Albino Swiss and DBA strains, modifies brain 5-HT and 5-HIAA almost to the same extent in the two strains, under both housing conditions (table 11). It may be of interest, though, that the reduction of brain TP reported in isolated Albino Swiss mice (Miller et aL, 1979;Pachter et al, 1978), does not appear to occur in isolated DBA mice, and PCPA restores brain TP level to normal in isolated Albino Swiss mice, having no significant effect on TP levels in grouped Albino and differentially housed DBA animals (table II). In general terms, the results obtained in these experiments do not support the hypoth esis of Woolley and Van Hoevetl (1965) that learning ability varies inversely with concentra tion of brain 5-HT.…”

Piracetam Activity May Differ According to the Age of the Recipient Mouse

“…Blood and brain were quickly collected, removed and stored on frozen C02 at -22 °C until assayed. To minimize the possible effect of circadian variations (Miller et al, 1979), the experimental procedures were always carried out between 09:00 and 10:00 in the morning.…”

“…Plasma and brain tryptophan contents were spectrofluorimetrically determined accord ing to a slightly modified version (Miller et al, 1979) of the revised method (Bloxam and Warren, 1974) of Denckla and Dewey (1967). Brain serotonin (5HT) and 5-hydroxyindoleacetic acid (5 HI A A) were also spectrofluorimetrically determined in the same tissue sample according to a procedure described earlier (Giacalone and Valzelli, 1969).…”

“…In contrast, no information on the effect of piracetam on brain monoaminergic mechanisms seems to be available as yet. Since the drug was recently shown to increase the tryptophan content of the mouse brain (Valzelli et al, 1979), the purpose of the present study is to investigate some behavioral effects of piracetam in young and old mice in relation to possible changes in serotonergic parameters of the brain.…”