Plasticity in crossed and uncrossed tuberomammillary-striatal projections in relation to recovery from behavioral asymmetries induced by hemivibrissotomy.

The influence of unilateral removal of the adult rat's vibrissae on crossed and uncrossed tuberomammillary-striatal projections was examined with the horseradish peroxidase tract tracing technique. Striatal afferents from the caudal magnocellular and the postmammillary caudal magnocellular subnuclei of the tuberomammillary nucleus were investigated. Between four and 20 days after clipping the vibrissae on one side, more retrogradely labeled cells were found in the crossed and uncrossed projections from both subnuclei to the caudate-putamen of the hemisphere opposite to vibrissae removal (i.e. the sensory deprived hemisphere) than in the projections to the caudate-putamen on the vibrissae-clipped side. In contrast, between one and three days after clipping the vibrissae no asymmetries in cell-labeling in these projections were found. This time-course of changes in the tuberomammillary-striatal projections is similar to the time-course of behavioral recovery reported after unilateral removal of vibrissae. Thus, the neural changes in these projections appeared at the point in time when rats recovered from behavioral asymmetries induced by vibrissae removal.