Out-of-phase development of dendritic spines in locus coeruleus and nucleus raphe dorsalis in rats of three age groups

Abstract

We have previously carried out morphometric Golgi studies of the 3 cell types, ovoid, multipolar and fusiform, which we have identified in the nucleus raphe dorsalis and nucleus locus coeruleus of rats. In the present study we have compared the dendritic spine densities of cells of the nucleus raphe dorsalis and nucleus locus coeruleus during development from 30 to 90 and 90 to 220 days of age in rats. Between 30 and 90 and 90 and 220 days of age dendritic spines on both primary and secondary dendrites of all 3 cell types in each nucleus showed exact out-of-phase development between the two nuclei though all 3 cell types within each nucleus were in phase with each other. Thus, all 3 cell types in the nucleus raphe dorsalis between 30 and 90 days showed a significant increase in spines on primary and secondary dendrites while all 3 cell types in the locus coeruleus during this period showed a significant decrease in primary and secondary dendritic spines. Between 90 and 220 days all cell types in the locus coeruleus showed a significant increase in dendritic spines while in the nucleus raphe dorsalis there was a signficant decrease in dendritic spines on 2 of the 3 cell types, the exception being a non-significant decrease in primary dendritic spines in the ovoid cells. This out-of-phase development of dendritic spines between locus coeruleus and dorsal raphe may have important functional implications since the dorsal raphe and locus coeru leus are mutually interactive and are involved, via their widespread projection systems, in many biochemical, physiological and behavioral regulations.