Aim: 

In our chronobiological study we have investigated the effects of oral administration of the essential amino acid L-methionine, which is precursor of the neurotransmitter acetylcholine, on common quails (Coturnix coturnix), animals that are characterized by being monophasic and active by day as humans.

Methods: 

The animals were kept under a constant 12:12 h light/dark cycle, fed ad libitum, and housed in separate cages equipped for activity recording. We have given by oral administration (1 h before turn off the light) a capsule with 30 mg of L-methionine during a week to the treated group versus basal group (without treatment). Additionally, we have compared the first day of treatment values (acute experiment) with the basal results. Actimetry technique (DAS24^®) was used to quantify the sleep/wake rhythm analysis. The statistical analysis of the data was descriptive ( DS) and inferential (T-Student).

Results: 

Data showed a significant increase (p<0.05) of the mean diurnal activity pulses on the group treated for a week (57.1 11.1 activity pulses) as well as on the first day of treatment (acute experiment) (56.1 22.9 activity pulses) versus the basal group (35.9 8.8 activity pulses). We did not find changes in nocturnal activity data between the treated group versus basal group, however there was a significant increase (p<0.05) on nocturnal acute results (12.5 12.7 activity pulses) versus basal group (10.0 12.7 activity pulses). In the chronobiological analysis, there was a significant increase on the parameter MESOR in the treated group and in the acute value (50.6% and 46.6%, respectively) versus basal group. Acrophase did not show changes, in all groups acrophase occurred at 13:45h.

Conclusion: 

In our study, the oral administration of L-methionine produced an increase of the diurnal activity; probably it was due to the stimulating neuromodulator action of the acetylcholine.