Ultrastructural and enzymic studies of cholinergic and non cholinergic synaptic membranes isolated from brain cortex

G. RODRÍGUEZ DE LORES ARNAIZ; M. ALBERICI; E. DE ROBERTIS

JOURNAL OF NEUROCHEMISTRY

WILEY-BLACKWELL PUBLISHING, INC

Año: 1967 vol. 14 p. 215 - 225

0022-3042

ULTRASTRUCTURAL AND ENZYMIC STUDIES OF CHOLINERGIC AND NON-CHOLINERGIC SYNAPTIC MEMBRANES ISOLATED FROM BRAIN CORTEX. GEORGINA RORIGUEZ DE LORES ARNAIZ, MARTHA ALBERICI and EDUARDDO DE ROBERTISInstituto de Anatomia General y Embriologia, Facultad de Medicina,Universidad de Buenos Aires(Received 26 November 1965)IN THE last few years a systematic electronmicroscopic study of various homogenization and cell fractionation procedures led to the isolation, within the crude mitochondrial fraction, of most of the nerve endings from brain. These were separated on a sucrose gradient from the myelin and free mitochondria and divided into two definite populations: one containing, and the other lacking, the three main components of the ACh system: i.e. bound ACh, AChE and ChAc. The noncholinergic nerve endings were found to contain glutamic acid decarboxylase. Another technique developed in this laboratory permitted the disruption by osmotic shock of nerve endings and the separation of synaptic vesicles from the bulk fraction containing mitochondria, myelin and synaptic membranes. Since more than 70 per cent of AChE was found in this bulk fraction, it was concluded that this enzyme is probably localized in the synaptic and nerve ending membranes. More recently the Na+-K+-activated ATPase was found to be concentrated in the cholinergic nerve endings with a distribution resembling AChE, while a K+-activated p-nitrophenylphosphatase was more concentratedin the non-cholinergic nerve endings. After osmotic shock both these enzymes were tightly bound to the synaptic membranes. In view of this background an obvious step seemed to be the development of techniques for the isolation and characterization of the synaptic membranes. Several procedures will be described together with the electron microscopic observations made on the various subfractions. These procedures have the advantage of starting from a fraction devoid of the bulk of membranous components, produced during the first homogenization, which sediment in the microsomal fraction. The enzymes AChE,Na+-K+-ATPase, K+-p-nitrophenylphosphatase, and GS-another membrane bound* Supported by grants from the Consejo Nacional de Investigaciones Cientificas y