Purkinje cells 5 -nucleotidase

ADENOSINE, 5 -NUCLEOTIDASE AND ADENOSINE DESAMINASE Adenosine-like immunoreactivity was found in rat Purkinje cells, using polyclonal anti-... 

Steady state concentrations of adenosine are maintained through the activities of only three enzymes, 5 -nucleotidase (5 -N), adenosine kinase and adenosine deaminase. Adenosine kinase and adenosine deaminase were located mainly in the soluble fractions of rat cerebellar homogenates, whereas 5 -N was present in subcellular fractions (Philips and Newsholme, 1979), mainly in the synaptosomal fraction (Marani, 1977). Adenosine deaminase-immunoreactivity in rat cerebellum was present with one out of five polyclonal sera prepared by Nagy et ah (1988). Staining was present in most Purkinje cells with a variation in intensity. Staining was observed in the Purkinje cell axons and terminals in the cerebellar and vestibular nuclei. The localization of 5 -N will be discussed below. 

Fig. 58. Light and electron micrographs of incubations for 5-nucleotidase according to Scott (1967). A, Detail of the light microscopic location of 5 -nucleotidase in uvula (IX) and pyramis (VIII). B. Electron microscopic location of 5 -nucleotidase reaction products in the subsurface cisternae of a Purkinje cell dendrite. C. Electron microscopic localization of 5 -nucleotidase in the spine apparatus of Purkinje cell dendritic spines (asterisks). D. Localization of reaction product in a parallel fiber bouton, synapsing on a Purkinje cell dendritic spine. Bars in A = 1 mm, in B,C = 0.5 fim, in D = 0.25 fmy. Marani (1977).

Fig. 59. 5 -Nucleotidase immunohistochemical staining of rat cerebellum. A. Immunofluorescence. B. PAP-method. Enzyme activity is predominantly found within the molecular layer on Bergmann glial fibers (long arrows). Purkinje cells are surrounded by fine rims of reaction product (small arrows). Within the granular layer 5 -nucleotidase activity is diffusely scattered between granule cells (arrow heads). Vibratome sections. C. Longitudinally sectioned Bergmann glia cell processes (B) of the molecular layer of rat cerebellum. Fine DAB reaction product is located on adjacent membranes of these processes (arrows). Bars in A,B = 50 /tm, in C = 0.5 nm. Schoen et al. (1987).

The possibility that zonally distributed differenees in size and connections of the Purkinje cells are correlated with specific chemical properties of these cells was first raised by Marani (Marani and Voogd, 1977 Marani, 1981, 1982a Marani, 1986) on the basis of the distribution of 5 -nucleotidase and acetyleholinesterase in the molecular layer and by Chan-Palay (1984) who reported a restricted distribution of certain peptides in subsets of Purkinje cells. More recently a complete pattern of alternating zones of immunoreactive and non-immunoreactive Purkinje cells was described by Hawkes and Leclerc (1986, 1987) with a Purkinje cell-specific antibody (anti Zebrin-I) in the rat and by Brochu et al. (1990) with anti-Zebrin II in the rat and other species (see Section... 

The distribution of the Zebrin-positive Purkinje cells was very similar to the distribution of the enzyme 5 -nucleotidase in the molecular layer of certain rodents (Eisenman and Hawkes, 1989). 

The distribution of 5 -nucleotidase (5 -N) (Section 3.5.) in alternate longitudinal bands of high and low enzyme activity in the molecular layer of the cerebellar cortex of the mouse (Scott, 1963,1964,1965,1967) was the first evidence for the biochemical compart-mentalization of the cerebellar cortex. The pattern of 5 -N-positive and -negative zones is complete in the sense that it is present in all the lobules of vermis and hemisphere and unequivocal, because, in the mouse at least, the bands are clearly delineated (Marani, 1986). The 5 -N band pattern is very similar, if not identical, to the more recently described distribution of Purkinje cells in the rat, reacting with Purkinje cell-specific monoclonal antibodies to Zebrin-I (mabQl 13) (Eisenman and Hawkes, 1989). 

The epitopes recognized by Hawkes family of monoclonal antibodies known as the anti-Zebrins are localized on Purkinje cells (see Section 3.1.8.). Zonal patterns that are identical or very similar to Zebrin I and II have been described for the distribution of 5 -nucleotidase (see above), the p75 low affinity nerve growth factor receptor protein in the rat (Section 3.1.10., Fig. 38), protein kinase C delta (Fig. 133) (see Section 3.1.5.) and the B30 antibody of Stainier and Gilbert (1989) (see Section 3.1.8.). Immunoreactiv-ity in mouse Purkinje cells for an antibody against HNK is partially congruent with the Zebrin negative Purkinje cells, but Zebrin+/HNK-l- Purkinje cells also exist (Hawkes, 1992 Eisenman and Hawkes, 1993). The similarity between the Zebrin pattern and the transient zonal patterns in the development of the Purkinje cell specific marker L7 is discussed in Section 6.2. 

A major drawback of many studies of the chemical neuroanatomy is that they were conducted in only one species, the rat. There is extensive evidence for species differences in the distribution of the synthetizing enzyme of acetylcholine (ChAT), muscarinic cholinergic receptors and acetylcholinesterase (see Section 3.10.), and there is reason to assume that a similar interspecies variability exists for other transmitter systems. The expression of Zebrin by certain subpopulations of Purkinje cells, and the zonal patterns in the distribution of 5 -nucleotidase, only occur in certain species. It is a fortunate coincidence for the experimental neuroscientist that the Zebrin zonal pattern is expressed in rats, but in other species like the cat or macaque monkeys all Purkinje cells are Zebrin-immunoreactive. Many species-differences in the chemical neuroanatomy of the cerebellum may be due to the selectivity of the antibodies employed in the im-munocytochemical techniques, but other differences may be real and may reflect true variations in structure or in the transmission and second messenger systems of the cerebellum. 

Hess DT, Hess A (1986) 5 -Nucleotidase of cerebellar molecular layer Reduction in Purkinje cell-deficient mutant mice. Dev Brain Res., 29, 93-100. 

---