Morphometric analysis of hippocampal pyramidal neurons in situ and in grafts developing in the anterior eye chambers of young and aged Wistar rats.

We performed a morphometric analysis of the somatic and nuclear areas in the pyramidal neurons of the hippocampal fields CA1 and CA3 in situ and in grafts developing for six weeks in the anterior eye chambers of young (3-to-9 wk.) and of aged (18-to-19.5 mos.) Wistar rats. The mean areas of the CA1 pyramidal somata and nuclei were significantly decreased in the aged animals in situ. The mean parameters of the CA3 pyramidal neurons were not changed, although their distribution was different (bimodal versus unimodal in the young animals). In both groups of recipients, the areas of CA1 neurons and of their nuclei were significantly larger in the grafted tissue than those found in situ. The areas of CA3 neurons did not show any difference in aged recipients and demonstrated only slight hypertrophy in young recipients. We concluded that the area sizes of the pyramidal cell bodies and nuclei in CA1 neurons are more sensitive than those of CA3 neurons to both aging and transplantation. The age of recipients did not significantly influence the growth and development of grafted pyramidal cells.

Growth of the hippocampal grafts in the rat anterior eye chamber: effects of age and strain of the recipients.

Hippocampal tissue (1 mm3) was taken from embryonal (E17-18) rats of Wistar stock in population breeding and grafted into anterior eye chamber of the four groups of recipients: young (3 weeks) and old (18 months) males of the same stock and of inbred strain WAG. Morphometric analysis of the grafts developing up to 12 weeks in oculo showed rapid initial growth in both groups of the young hosts during the first three weeks, and limited increase of the graft volume during next three weeks. The start of growth was significantly retarded in the old hosts, but this was partly compensated by prolonged increase of the graft volume during the later stages. Both mean and maximal finite volume were much smaller in both WAG groups. The hippocampal grafts in these groups had rounded (not elongated, as in Wistar groups) shape and showed tendency to fragmentation and resorbtion at the late stages. Histological analysis revealed well organized layer of the pyramidal cells in the both Wistar groups and nearly complete absence of neuronal organization into layer in both WAG groups. Possible role of trophic and immune factors in development of intraocular grafts is discussed.