OLFACTORY-BULB RECOVERY AFTER EARLY SENSORY DEPRIVATION

Olfactory bulbs retain the ability to acquire new neurons throughout l ife. Unilateral olfactory deprivation during the first postnatal month in rats results in a dramatic reduction in the size of the experiment al olfactory bulb. Part of this reduction is attributable to the death of neurons and glia. To examine the regenerative capacity of the juve nile olfactory bulb, we developed a technique for reversible olfactory deprivation. Reversible blockade from postnatal day 1 (P1) to P20 or P30 results in reduced bulb volume and tyrosine hydroxylase immunostai ning, and decreased depth in the olfactory mucosa. In another experime nt, normal stimulation was restored for varying periods of time, and e xperimental and control bulb volumes were measured. Recovery of bulb s ize occurs after 40 d of normal stimulation. Rats injected with a thym idine analog to label dividing cells during the recovery period reveal ed that rescue results at least in part from the addition of new neuro ns and glia, Thus, cells born after the return of normal levels of env ironmental stimulation can replace some of the neurons and glia that a re lost during olfactory deprivation. This system can be used to study mechanisms that underlie neuronal regeneration in the maturing mammal ian brain.