Nerve-ending membrane

As mentioned in section 4.3.3, there are two kinds of a receptor in brain and peripheral tissues. The crucial experiments have shown that brain tissue prelabeled with pH]NE will release neurotransmitter upon electrical stimulation or exposure to K+. The release is reduced by the a agonist clonidine (4.42) and stimulated by the a antagonist yohimbine (4.43). Since the adrenoreceptor involved in this latter experiment plays a vital role in modulating neurotransmitter release, it must be presynaptic and located on the nerve-ending membrane. A similar selectivity has also been shown by peripheral tissues (heart, uterus), leading to the distinction of aj (postsynaptic) and (presynaptic) adrenergic receptors. There are also presynaptic [3 receptors, which show a feedback regulation opposite to that of the ttj receptors that is, their excitation by a neurotransmitter increases NE release. 

Gangliosides and Associated Enzymes at the Nerve-Ending Membranes... 

Cotman, C., Mahler, H. R. and Anderson, N. G. (1968) Isolation of a membrane fraction enriched in nerve-end membranes from rat brain by zonal centrifugation. Biochim. biophys. Acta (Amst.), 163, 272-275. 

From studies on the incorporation of [3H]-leucine into proteins of the synaptic vesicles and nerve ending membranes, a half life of 20-22 days was calculated (Von Hungen et al., 1968). Lapetina et al. (1969) found a more rapid turnover for brain phospholipids, though different parts of the molecule seemed to turn over at different rates. Acylation of lysophospholipids to diacyl-phospholipids seems to be carried... 

Synaptic vesicles, isolated from rat brain cortex, and cholinergic vesicles, isolated from the electric organ of Torpedo nobiliana, were broken down by a phospholipase A from cobra venom. The breakdown was accompanied by a release of acetylcholine. Morphological analysis revealed membrane fragments about one-third the size of the vesicle circumference. Subcellular fractions enriched in nerve ending membranes showed some phospholipase A activity. On the basis of these findings models of transmitter release, involving specific alterations of lipid components in the vesicular membrane, are discussed. 

Selective serotonin reuptake inhibitors A group of drugs that selectively inhibit the serotonin transporters of the nerve ending membrane... 

Very recent X-ray examination by Wilkins et al. (1971) of several membranes suspended in water has shown that their main structural feature is the lipid bilayer. The preparations examined included erythrocyte ghosts, nerve-ending membranes, sarcoplasmic reticulum, E. coli plasma membrane, and that of Halobacterium cutiru-brum. 

Yohe, H. C., and Rosenberg, A., 1978, Effect of neurotoxic divalent cations on the activity of the intrinsic nerve ending membrane associated sialidase of bovine brain, Neurochem. Res. 3 101-113. 

Schengrund, C.-L., and Rosenberg, A., 1973, Effect of cations on the sialidase activity of nerve ending membranes, Trans. Am. Soc. Neurochem. 4 90. 

The exact mechanism of P-btx is not yet known. But it may be that phospholipase A creates a hole in the nerve end membrane and Ca " flows to the cytoplasm. As a result, vesicles containing the nerve transmitter acetylcholine discharge it. The nucleotide sequence encoding P-btx A2-chain has been determined (Danse and Gamier, 1990). 

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