Age-related changes of neurochemically different subpopulations of cardiac spinal afferent neurons in rats

The number of cardiac spinal afferent neurons decreased in senescence to 15% of that found in young rats (1604 vs. 248). The size of neuronal soma as well as proportion of IB4 + neurons increased significantly, whereas the proportion of N52 + neurons decreased significantly in senescence. Unlike somatic spinal afferents, neurochemically different populations of cardiac spinal afferent neurons experience morphological and neurochemical changes related to aging. A major decrease in total number of cardiac spinal afferent neurons occurs in senescence. The proportion of N52 + neurons decreased in senescence, but it seems that nociceptive innervation is preserved due to increased proportion and size of IB4 + unmyelinated neurons.