Opposite effects of tryptophan intake on motor activity in ring doves (diurnal) and rats (nocturnal).
The role of l-tryptophan as precursor of serotonin and melatonin synthesis on activity-rest rhythm was studied in ring doves, Streptopelia risoria, as a representative of diurnal animals and rats, Rattus norvegicus, as a typical nocturnal one. The animals were housed in cages equipped for horizontal activity recording in a thermostatized chamber and submitted to a 12/12h light/dark photoperiod (lights on at 08:00 h). After acclimatization, the animals received vehicle (methylcellulose) and l-tryptophan (240 mg/kg) by esophagic cannula 2h before the onset of either light or dark phase. Also, oral melatonin (2.5mg/kg) was tested for comparative purposes. After nocturnal l-tryptophan administration, rats showed increased activity (149%), while the opposite occurred in ring doves (39% decrease). No significant changes were found after diurnal l-tryptophan intake in either species. Melatonin produced effects similar to those of l-tryptophan. These results suggest that the effects of l-tryptophan administration are dependent on the nocturnal/diurnal habits of the studied species and, most probably, are mediated by increased melatonin synthesis.
Aparicio
Sara
S
Laboratori de Neurofisiologia, Departament de Biologia Fonamental i Ciènces de la Salut., Universitat de les Illes Balears, Spain.
Garau
Celia
C
Nicolau
María C
MC
Rial
Rubén V
RV
Esteban
Susana
S
D000818:Animals; D005075:Biological Evolution; D002940:Circadian Rhythm / Q000502:physiology*; D010856:Columbidae / Q000502:physiology*; D020869:Gene Expression Profiling; D016762:Genes, fos / Q000187:drug effects; D008297:Male; D008550:Melatonin / Q000378:metabolism; D009043:Motor Activity / Q000187:drug effects*; D010507:Periodicity; D017440:Photoperiod; D051381:Rats / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D012890:Sleep; D013997:Time Factors; D014364:Tryptophan / Q000008:administration & dosage*; D014851:Wakefulness / Q000187:drug effects
D012701:Serotonin; D014364:Tryptophan; D008550:Melatonin