Trans-synaptic modulation of Purkinje cell plasma membrane organization by climbing fiber axonal flow

Destruction of the inferior olivary nucleus in the rat by thermocoagulation results in the degeneration of climbing fibers in the cerebellar cortex. Under these conditions the plasma membrane of Purkinje cells was selectively affected at the level of the spines on large dendrites (LD spines), the postsynaptic targets for climbing fibers. The number of small (less than 10 nm) non-junctional intramembrane particles (IMP) was significantly decreased in E-faces during the first 3 days following the lesion (47% of control IMP values). Later, the number of IMPs progressively recovered to reach 67% of the control IMP values 1 month following the lesion. IMP numbers in the P-face and in the postsynaptic junctional aggregates of the E-face were unaffected by destruction of climbing fibers. Following injection of colchicine into the inferior olivary nucleus, a treatment that inhibits axonal transport in climbing fibers, a selective decrease in IMP numbers on the E-faces of LD spines was also found. The maximal decrease was found during the first 10 days after injection (48% of control values), and then the number of IMPs gradually increased to reach control values by 90 days post-injection. In the case of colchicine treatment also, the reduction in the number of IMPs affected selectively a class of non-junctional small IMPs, less than 10 nm in diameter. These data show that there is a similar selective modification in the membrane structure of Purkinje cells, not only following destruction of climbing fibers by thermocoagulation, but also following inhibition of axonal flow in climbing fibers by colchicine injection.(ABSTRACT TRUNCATED AT 250 WORDS)