The calcium binding proteins parvalbumin and calbindin‐D 28K form complementary patterns in the cat superior colliculus

Abstract

Parvalbumin (PV) and calbindin-D 28K (CaBP) are calcium binding proteins involved in calcium regulation in the brain. In some regions they coexist in the same neuron, while in other regions they are found in different cell types. We have studied the distribution and morphology of PV labeled neurons in the cat superior colliculus (SC) with antibody immunocytochemistry and compared this labeling to that of CaBP. PV neurons were concentrated in a dense tier within the deep superficial gray and upper optic layers. Scattered PV neurons also were found within the deep layers of SC. By contrast, CaBP neurons were concentrated in three tiers: one within the zonal and upper superficial gray layers, a second within the deep optic and upper intermediate gray layers (IGL), and a third within the deep gray layer. The distribution of PV neurons is thus complementary to that of CaBP neurons, with the CaBP cell tiers bordering the dense tier of PV neurons. PV neurons varied in size and morphology. The average diameter of labeled cells was 20 microns, almost twice the size of CaBP neurons. The cells were predominantly round, vertical fusiform, or stellate, and included the very large neurons found scattered in the IGL. Horseradish peroxidase injections into the lateral geniculate nucleus, the lateral posterior nucleus, the opposite superior colliculus, the dorsal lateral pontine gray nucleus, and two descending pathways--the crossed predorsal bundle and the tecto-ponto-bulbar tracts--each labeled SC neurons that were also labeled by PV. A large percentage (84%) of projection neurons contained PV. This result also differs from CaBP neurons in SC, most of which are interneurons. Two antigen double-label experiments did not produce any cells that contained both PV and CaBP. The two calcium binding proteins thus reveal a unique sublaminar organization in SC that consists of alternating small cell interneuron groups and large cell projection neuron groups.

CalbindinD28k- and parvalbumin-immunoreactive neurons form complementary sublaminae in the rat superior colliculus

“…The cat, as far as we are aware, is the only other species in which the distributions of CB and PV have been compared directly in the same experiments (Mize et al, 1992). In the cat, CaBPs are distributed in a pattern of alternating sublaminar tiers that is similar to that seen in the rat but that is far more spatially constricted.…”

“…Overall, the distribution of PV is complementary to that of CB throughout the cat SC, with two tiers of PV neurons lying between three tiers of CB cells (Mize et al, 1992). This complementarity of PV and CB expression raises the interesting prospect that there may be functional sublamination of the SC that is separate from the more traditional layers that have been identified by using conventional stains.…”

“…The W cells in cat are analogous to the K cells in primates (Casagrande, 1994). Mize et al (1992) also found a band of PV-immunoreactive cells (PV-cells) in the deep SGL and upper optic layer (OL), a region of the cat SC that receives input from Y retinal ganglion cells (Berson and McIlwain, 1982). The parallel pathways involved in somatosensory processing also pass through the SC, and different components of this pathway can also be distinguished by using CB and PV immunocytochemistry (Hendry et al, 1989;Bennett-Clarke et al, 1992;Kevetter, 1996).…”

“…Calbindin D28k (CB) and parvalbumin (PV) have proved to be particularly useful for distinguishing separate populations of neurons. In many regions of the brain, these two proteins have mutually exclusive expression and are distributed in complementary patterns (e.g., Mize et al, 1992;Johnson and Casagrande, 1995). They have also been shown to distinguish separate populations of ␥-aminobutyric acid (GABA)ergic neurons (Celio, 1986(Celio, , 1990Toth and Freund, 1992) as well as projections from interneurons (Mize et al, 1992;Lane et al, 1997).…”

Distribution of calretinin in the superficial layers of the mouse superior colliculus: Effect of monocular enucleation

“…Thus, the calciumbinding protein, calbindin D28K, is found in cells that are located in three layers of the cat superior colliculus (Mize et al, 1991). Parvalbumin-immunoreactive cells formed a single, dense band in the deep superficial gray and optic layers with loosely scattered cells in the deep layers of the cat (Mize et al, 1992). Calretinin has also been localized in some animals.…”