The effect of methionine and S-adenosylmethionine on S-adenosylmethionine levels in the rat brain.

OBJECTIVE S-Adenosylmethionine (SAMe) is a major methyl donor in the brain and is also an antidepressant with few reported side effects; however, SAMe is relatively expensive and unstable. Brain SAMe can be increased by giving methionine to rats, raising the possibility that methionine may be an antidepressant. We aimed to study whether SAMe and methionine, when given orally to rats, could raise levels of SAMe in the central nervous system (CNS). We also aimed to test the relative abilities of SAMe and methionine to increase tail-flick latency after a thermal stimulus. This test was used to measure changes in CNS function. METHODS Rats were given SAMe and methionine orally at various doses, and biochemical and behavioural testing was carried out at intervals up to 6 hours later. RESULTS Methionine raised SAMe levels in various regions of the CNS and increased tail-flick latency, both at lower doses than SAMe. CONCLUSION Methionine should be tested for antidepressant properties in humans.