Nerve growth factor increases nicotinic ACh receptor gene expression and cur - rent density in wild

There are disclosed new solid catalyst-forming components for use in preparing catalysts for the stereoregular polymerization of alpha-olefins containing at least 3 carbon atoms, mixtures of alpha-olefins with one another and/or with ethylene, said components being obtained by reacting (A) AT LEAST ONE HYDROCARBON-SOLUBLE HALOGENATED Ti compound; (B) A PRODUCT COMPRISING A Mg dihalide obtained by decomposition of an adduct of at least a Mg dihalide and an electron-donor compound present in the adduct in an amount of at least 0.5 mole per mole of Mg dihalide, the decomposition product being characterized in that, in its X-rays powder spectrum, instead of the diffraction line of maximum intensity which appears in the X-rays powder spectrum of the normal Mg dihalide, a halo appears whose intensity maximum is shifted with respect to said line, and (C) AN ELECTRON-DONOR COMPOUND WHICH DOES NOT CONTAIN ACTIVE HYDROGEN ATOMS.