$(document).ready( function(){
$('#nuevanew').toggle(ction() {
$(this).text('Cerrar');
$("#cpNovaNoticia").slideDown("slow");
},
function() {
$(this).text('Nueva noticia');
$("#cpNovaNoticia").slideUp("slow");
}
);
});
<button type="button" id="nuevanew" class="destacado">Nueva noticia</button>

