This is what I've done

view

<% for micropost in @microposts %>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function(){
 
        $(".slidingDiv<%= micropost.id %>").hide();
        $(".show_hide<%= micropost.id %>").show();
 
    $('.show_hide<%= micropost.id %>').click(function(){
    $(".slidingDiv<%= micropost.id %>").slideToggle();
    });

});
</script>


<%= link_to image_tag('Comment.png', :mouseover => "Comment-Over.png", :class => "show_hide"),  "#" %>
<div class="slidingDiv<%= micropost.id %>">
	<%= render  :partial => 'microposts/display', :locals => { :micropost => @micropost } %>      
<a href="#" class="show_hide<%= micropost.id %>">hide</a>

<% end %>