Calbindin D-28k and parvalbumin in the rat nervous system

Abstract

This paper describes the distribution of structures stained with mono- and polyclonal antibodies to the calcium-binding proteins calbindin D-28k and parvalbumin in the nervous system of adult rats. As a general characterization it can be stated that calbindin antibodies mainly label cells with thin, unmyelinated axons projecting in a diffuse manner. On the other hand, parvalbumin mostly occurs in cells with thick, myelinated axons and restricted, focused projection fields. The distinctive staining with antibodies against these two proteins can be observed throughout the nervous system. Calbindin D-28k is primarily associated with long-axon neurons (Golgi type I cells) exemplified by thalamic projection neurons, strionigral neurons, nucleus basalis Meynert neurons, cerebellar Purkinje cells, large spinal-, retinal-, cochlear- and vestibular ganglion cells. Calbindin D-28k occurs in all major pathways of the limbic system with the exception of the fornix. Calbindin D-28k is, however, also found in some short-axon cells (Golgi type II), represented by spinal cord interneurons in layer II and interneurons of the cerebral cortex. It is also detectable in some ependymal cells and abundantly occurs in vegatative centres of the hypothalamus. The “paracrine core” of the nervous system and its adjunct (1985, Nieuwenhuys, Ghemoarchitecture of the Brain. Springer, Berlin) is very rich in calbindin D-28k. The distribution of calbindin D-28k-positive neurons is very similar to that of the dihydroperydine subtype of calcium channels. Most of the cells containing calbindin D-28k are vulnerable to neurodegenerative processes. Parvalbumin-immunoreactive neurons have a different, and mostly complementary distribution compared with those which react with calbindin D-28k antisera, but in a few cases (Purkinje cells of the cerebellum, spinal ganglion neurons), both calcium-binding proteins co-exist in the same neuron. Many parvalbumin-immunoreactive cells in the central nervous system are interneurons (Golgi type II) and, to a lesser extent, long-axon cells (Golgi type I), whereas conditions are vice versa in the peripheral nervous system. Intrinsic parvalbuminic neurons are prominent in the cerebral cortex, hippocampus, cerebellar cortex and spinal cord. Long-axon parvalbumin-immunoreactive neurons are, for example, the Purkinje cells, neurons of the thalamic reticular nucleus, globus pallidus, substantia nigra (pars reticulata) and a subpopulation among large spinal-, retinal-, cochlear- and vestibular ganglion cells. Parvalbumin is rich in cranial nerve nuclei related to eye movements. In addition to nervous elements, parvalbumin immunoreactivity occurs in a few ependymal cells and in some pillar cells of the organ of Corti. In contrast to calbindin D-28k, parvalbumin is virtually absent from vegetative centres and pathways. Parvalbumin co-exists with GABA in cortical neurons and is, in general, preferentially associated with “fast-firing” neurons. Whole functional systems are revealed by either parvalbumin or calbindin D-28k immunohistochemistry. Parvalbumin, for example, occurs in the whole chain of neurons of the epicritic sensibility in the somatosensory system. Calbindin D-28k, on the other hand, occurs in the whole taste pathway. With antibodies against calbindin D-28k and parvalbumin it is possible to reveal at least two as yet undescribed brain nuclei: one in the hypothalamus (parvalbumin 1), the second in the medulla (calbindin D-28k 1). Calbindin D-28k and parvalbumin are evenly distributed within the various domains of the same neuron, but in some instances their levels vary between soma and cell processes. The immunostaining with calbindin D-28k and parvalbumin antisera show gradations in intensity among neurons belonging to different populations, a phenomenon compatible with the presence of varying concentrations of these proteins. Calbindin D-28k and parvalbumin are excellent new neuroanatomical markers which can be utilized to selectively visualize certain neurons and pathways in the central nervous system and peripheral nervous system.