Immunohistochemistry for leptin in brain tissue. Rats injected with saline solution, lactic acid or LS were euthanized 48 hr after injections and their brains were fixed in formalin immediately after euthanasia. Cytoplasmic immunostaining for leptin (arrows) was stronger in neurons of thalamus in LS-injected animals (B) than in corresponding cells of rats injected with saline (A). No counterstain. Magnification × 200.