well i ejaculate very quickly and the following research should answer your question

"SEXUAL AROUSAL and FUNCTION

Histidine is involved in the function of the thalamus and hypothalamus glands, and orgasm is triggered when histamine is released from the mast cells in the genitals. Histamine also causes the sexual flush that occurs during arousal. Many women fail to achieve sexual pleasure and orgasm, and often other treatments including psychotherapy may be unsuccessful. This problem may be a result of a biochemical imbalance, since sufficient histamine must be present in order to trigger an orgasm. Deficiencies of L-Histidine will effect histamine levels.

Supplementing with L-Histidine will increase histamine levels as proved by Carl Pfeiffer, M.D., and Ph.D. in his research on non-orgasmic women. He administered doses of 500mg. of L-Histidine (1) before each meal (for a total of 3 per day) restoring sexual pleasure in women. (He also helped women who had irregular periods become regular by giving doses of 4g. per day).

Dr. Pfeiffer noted that males who had excessive L-Histidine levels had the problem of premature ejaculation. He gave these men supplementation of 500 mg. of L-Methionine along with 500 mg. of magnesium and 50mg. of vitamin B6. This helped normalize the levels of Histidine, and alleviated the problem of premature ejaculation. Those taking L-Methionine should also take a B complex with folic acid to help prevent excessive homocysteine levels. (Take 2 Montiff B Complete daily - 1 in the morning and 1 in the evening to get sufficient folic acid and B 6.)."