Pineal and habenula innervation altered by septal lesions.

Septal lesions result in a measurable increase in sympathetic innervation of the hippocampus. The cell bodies of origin of these sympathetic fibers reside in the superior cervical ganglion (SCG), which also projects to the pineal gland and medial habenula. If the SCG neurons which project to the pineal are the same neurons which sprout into the hippocampus after septal lesions, a common cell body reaction might mediate changes in innervation of the pineal. If cholinergic denervation is the principal trigger of hippocampal sprouting, a similar response might be observed in habenula which is also innervated cholinergically from septal area neurons. Pineal and medial habenula innervation were quantified using a new microfluorometric method at 20 post-lesion intervals following septal lesions. Changes in intensity and density of innervation were correlated with time in days after the lesions. Pineal intensity, pineal density, and habenula intensity exhibited statistically significant correlations with time in days after septal lesions. These changes occurred during the growth of sympathohippocampal fibers. The data suggest that a common cell body reaction mediated the changes in pineal and the sympathetic sprouting in the hippocampus.