Target tissue innervation in 3-B− mice compared to 3+B− mice.

<p>+ = highly reduced innervation relative to adult 3+B− control mice.</p><p>+++ and ++ = intermediate innervation relative to adult 3+B− control mice.</p><p>++++ = similar innervation relative to adult 3+B− control mice.</p><p>p values, Student's t test, from semi-quantitative TH immunofluorescence.