**6. The olfactory bulbectomy model in rats: a model of what?**

Although the OBX model in rats (and to a lesser extent mice) is primarily known for its detection of antidepressant activity in a molecule, the model has several other interesting features, in particular, to study degenerative processes in the brain after removing the olfactory bulbs. OBX leads to widespread trans-neuronal degeneration, cognitive decline, reduced volumes of several brain structures (hippocampus, nucleus caudatus and amygdala), disruption of the blood-brain barrier and several other serious changes [7, 15]. All these aspects make the OBX model in rats attractive, as has also been illustrated in the present chapter with regard to onset of behavioral changes after OBX, but also neuroplastic changes after long-term administration of antidepressants. Whether these changes reflect effects on neurodegenerative processes is not clear yet. Much research using the model is needed to show its further contribution to neuroscience.
