Lesions do not provoke GFAP-expression in the GFAP-immunonegative areas of the teleost brain

In the mammalian and avian brains the predominant astroglial elements are astrocytes, and the distribution of GFAP-immunopositivity is rather uneven, some large brain areas being almost devoid of GFAP-immunopositivity. In these areas however, an intense GFAP-immunopositivity appears following injury. In the teleost brain most of the areas are GFAP-immunopositive and ependymoglia predominates. However, a large area, the layer of the sensory neurons in the vagal lobe, is devoid of GFAP. The question arises, whether the lack of GFAP-immunopositivity in the teleost brain is also due to the repression of the GFAP-production, as in birds and mammals, or due to the lack of cells capable of expressing GFAP. To answer this question, stab wounds were made in the vagal lobe of goldfish, as well as in the tectum, in which moderately dense but highly organized GFAP-immunopositive glia has been detected in intact animals. In the layer of the sensory neurons in the vagal lobe no GFAP-immunopositivity appeared even after lesions had been introduced. In the tectum, a rather slight increase of the intensity of the immunostaining was observed in the glial fibers near the lesions but no typical reactive glia similar to that found in mammals or birds, was observed. The results suggest that a lesion does not provoke GFAP-expression in GFAP-immunonegative brain areas in teleosts, in contrast to what is observed in mammals and birds.