“…This organ is presumed to serve as an extraretinal phototransducer involved in the retinal± pineal axis (in Payne, 1994) and is intimately associated with eyes and opens by a duct onto the surface of the nictitating membrane (Sakai, 1981;Djeridane, 1992Djeridane, , 1994Djeridane, , 1996. In rodents, the Harderian gland synthesizes lipids (Seyama et al, 1992), photosensitive porphyrin pigments (Spike, Payne and Moore, 1992), and indoles (MenendezPelaez and Buzzell, 1992;Menendez-Pelaez et al, 1993;Djeridane et al, 1999a,b), mainly melatonin (Djeridane et al, 1998(Djeridane et al, , 2000. The organs also exhibit activity of serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), enzymes necessary for melatonin production (Pe Âvet et al, 1980;Balemans et al, 1983;Menendez-Pelaez and Buzzell, 1992;Menendez-Pelaez et al, 1993).…”