The neuronal structure of the mamillary nuclei in guinea pig: Nissl, Klüver-Barrera and Golgi studies

Abstract

The neurons of the mamillary body of adult guinea pigs were classified into four types: Type 1 — unidendritic cells with rounded perikarya (7–16 µm) and one thick primary dendrite, mostly dividing into tortuous secondary branches; Type 2 — bipolar cells: curly or simple ones with fusiform perikarya (13–22 µm); the curly-bipolar neurons possess 2 primary dendrites which may divide, even into tertiary dendrites, but each of them runs in screw-like or bending patterns; the simple-bipolar neurons have slender dendrites following a more straight route; Type 3 -multipolar cells with cap-like perikarya (10–20 µm) and 2–3 dendritic trunks originating from the base of the perikaryon and running in a wavy pattern; sometimes their dendrites possess spiny-like protrusions; Type 4 — multipolar cells with triangular or quadrangular perikarya (13–28 µm) and 3–4 dendritic trunks, poorly ramified, having a rather rectilinear course. In all types of neurons, dendritic spines are absent or rare. The majority of these neurons have a short impregnated axon originating from the perikaryon or primary dendrite.