Ontogenesis of olivocerebellar relationships. II. Spontaneous activity of inferior olivary neurons and climbing fibermediated activity of cerebellar Purkinje cells in developing XXXX .

@entity35 @entity41286 @entity1577
During development of vertebrate cerebellum, a multiple innervation of each Purkinje cell (PC) by several climbing fibers (CFs) (Cr  pel, F., J. Mariani, and N. Delhaye-Bouchaud (1976) J. Neurobiol. 7: 567-578; Mariani, J., and J. -P. Changeux (1981) J. Neurosci. 1: 696-702) precedes the one-to-one relationship characteristic of the adult stage. In the present study, the spontaneous activity of inferior olivary neurons (whose axons constitute the CFs) and the spontaneous activity elicited in PCs by the @entity1577 system were investigated in developing @entity35 . Extracellular unitary recordings were obtained in medial and dorsal accessory olives from 249 neurons from 1-day-old to adult animals. The mean discharge rate varied from 0.19 spike . @entity41286 on day 1 to 1.69 spikes . @entity41286 on postnatal day 21 and 1.78 spikes . @entity41286 in adult animals. Although the spontaneous discharge was low, interspike interval histograms were constructed for a sample of cells. Their modal value varied from a mean value of 660 msec on day 1 to 250 msec in the adult with, however, marked variations at each age in the young animals. Intracellular recordings from PCs were performed in @entity35 ranging in age from 5 to 15 postnatal days. The spontaneous (i.e., asynchronous) discharge of excitatory postsynaptic potentials mediated neurons at the same age. The main results are the following: (1) In PCs innervated by one @entity1577 , the mean frequency of @entity1577 -EPSPs was similar to the discharge of inferior olivary neurons; (2) in PCs innervated by several CFs, the mean discharge of @entity1577 -EPSPs was much higher than the discharge of inferior olivary neurons; (3) as a whole, the @entity1577 -mediated activity of PCs decreased from day 5 to day 11, while the multiple innervation disappeared; from then on, the activity increased with the maturation of inferior olivary neurons until adult values. The ratio of the frequencies of @entity1577 -EPSPs and olivary neurons discharges gives an approximate mean number of @entity1577 collaterals per PC at each age; it varied from 3.6 on day 5 to values close to 1 on day 11 and the following days.
