“…Cerebrospinal fluidcontacting neurons containing immunoreactive GAL were reported before in teleosts (Holmqvist and Ekstrom, 1991), anurans (Lazar et al, 1991;Olivereau and Olivereau, 1992) and the turtle (Jimenez et al, 1994). In lampreys, CSFcontacting neurons have been found to be immunoreactive to antisera against several substances such as serotonin (Brodin et al, 1988a(Brodin et al, , 1990aPierre et al, 19921, somatostatin (Wright, 1986;YaAez et al, 1992), substance P (Nozaki and Gorbman, 19861, cholecystokinin (Brodin et al, 1988b), gonadotropin-releasing hormone (King et al, 1988), the molluscan cardio-excitatory tetrapeptide (Ohtomi et al, 1989) neurotensin (Brodin et al, 1990b), histamine (Brodin et al, 1990a), dopamine and tyrosine hydroxylase (Pierre et al, 19941, and opsins (Garcia-Fernandez and Foster, 1994). The brain of lamprey is considered to have conserved many characteristics of the primitive vertebrate brain (Nieuwenhuys, 1977).…”