β-Bungarotoxin-induced cell-death of neurons in chick retina

Abstract

The cytotoxicity of β-bungarotoxin (β-BTX), a snake venom neurotoxin with phospholipase A 2 activity, for chick neurons was investigated using organ and monolayer cultures of retina. β-BTX led to a marked reduction in the total activities of choline acetyltransferase and glutamate decar☐ylase of retina cultures at concentrations as low as 100 pM. The total activity of lactate dehydrogenase was, however, much less affected by β-BTX. Also, the total activity of tyrosine hydroxylase of organ-cultured retina decreased only at 30–50 fold higher concentrations of the toxin. The total activity of the glial marker glutamine synthetase was not changed by β-BTX. In contrast to this selectivity for neurons displayed by β-BTX, non-neurotoxic phospholipases A 2 from bee venom and porcine pancreas led to a simultaneous loss of both neuronal and glial marker enzymes. Light and electron microscopy of organ-cultured retina showed that only cells in the ganglion cell layer and the inner third of the amacrine cell layer degenerated after incubation with β-BTX. In the toxin-sensitive cells, the Golgi apparatus and the endoplasmatic reticulum appeared the first subcellular structures to be affected. It is concluded that β-BTX preferentially recognizes and/or destroys cholinergic and GABAergic cells in the amacrine and ganglion cell layers of the developing chick retina. This toxin may thus be a useful probe to investigate cell surface properties of cholinergic and GABAergic neurons in the chick central nervous system.