Recovery of olfactory function after massive degeneration of olfactory neurons in amphibian larvae: A possible role for brain-derived neurotrophic factor.

YOVANOVICH CA; HEER T; JUNGBLUT L; POZZI A; PAZ DA

Huerta Grande - Córdoba

Taller; I Reunión Conjunta de Neurociencias; 2009

Sociedad Argentina de Investigación en Neurociencias

Amphibian larvae represent an excellent experimental model to study the ability of the olfactory epithelium (OE) to regenerate its neuronal population continuously throughout life. We have developed an experimental design consisting in immersion of Rhinella arenarum larvae in zinc sulphate (ZnSO4) that provokes a massive degeneration of the olfactory tissue. We have previously observed that the normal architecture of the OE is restored by the third day after ZnSO4 treatment. However, the functionality of this recovered epithelium remained to be analyzed. Thus, we designed a simple and reliable method to test larvae behavior that consists in analyzing their responsiveness to an olfactory stimulus that indicates the presence of food. Our data show that shortly after treatment there is no response to the olfactory stimulus, whereas since the second day and thereafter the responsiveness is restored and exhibits the same timing that the response registered for control animals. These results suggest that the sensorial ability of the OE recovered after injury is, at least for this kind of stimulus, as efficacious as that achieved during the normal physiological turnover of the olfactory neurons. We next addressed the issue of which factor(s) are involved in this re-establishment of olfactory functionality. As we had previously observed that a strong brain-derived neurotrophic factor (BDNF) immunostaining is present in specific regions of the OE and in the olfactory nerves immediately after ZnSO4 treatment (in contrast to control animals in which it is absent) we screened the evolution of this staining pattern during recovery of the OE. Here we show that BDNF staining in the olfactory nerves fades away by the second day of recovery, whereas staining in the OE remains unchanged during this time lapse. These results suggest that BDNF plays some role during the reconnection of the olfactory nerves to the olfactory bulb that allows restoration of the responsiveness to olfactory stimuli, whereas in the OE it may have a longer term effect.