Cytoarchitecture and Staining for Acetylcholinesterase and Zinc in the Visual Cortex of the Parma Wallaby <i>(Macropus parma)</i>

Abstract

Cytoarchitecture and distributions of acetylcholinesterase-containing fibers and zinc-containing neuropil are described in the primary visual cortex of a metatherian, the Parma wallaby (Macropus parma). Although some cytoarchitectural features of layer III suggest that a subdivision and a corresponding layer IIIa-c terminology may be employed, neurochemistry is more concisely described using a simple layer I-VI terminology. Horizontal acetylcholinesterase-containing fibers in layer I take on a vertical course as they pass through layer II to form a reticulate pattern in upper layer III. Fibers gather into vertical groups in lower layer III and, markedly, in layer IV. No dominant orientation is seen in layer V, whereas an horizontal course is often seen in layer VI. Zinc-containing neuropil is very dense in layers I, II and upper III, where particles are homogeneously distributed. Particles begin to form strands in lower layer III and form conspicuous vertical clusters in an otherwise almost unstained layer IV. There is a sharp transition to a densely and homogeneously stained layer V, a decrease in staining intensity in layer VI, and a further decrease within layer VI towards the white matter. The distribution of acetylcholinesterase-containing fibers in M. parma, a metatherian representative, adds to the number of species-specific patterns observed in eutherians. The distribution of zinc-containing neuropil in M. parma resembles the consistent pattern seen in eutherian species. Thus, pathways incorporating zinc, as a putative neuromodulator of excitatory amino acid receptor responses, may be organized similarly in the cortex of meta- and eutherians.

Architectonic Subdivisions of Neocortex in the Gray Squirrel (Sciurus carolinensis)

“…Yet, variations in staining patterns produced with these antibodies have not often been used as criteria for parcellating the neocortex. Similarly, the distribution of zinc-enriched terminals has been described in the neocortex of rodents, such as mice (Garrett et al, 1991; Brown and Dyck, 2004; Czupryn and Skangiel-Kramska, 1997), rats (Ichinohe et al, 2003; Miro-Bernie et al, 2006), and in the visual cortex of parma wallabies (Garrett et al, 1994). These zinc-enriched terminals originate from a subset of glutamatergic neurons in the neocortex, as well as neurons in the claustrum and amygdala, and they are not found in terminals of neurons that originate in the thalamus (Danscher, 1982; Frederickson and Moncrieff, 1994; Frederickson et al, 2000, Ichinohe et al, 2003; Ichinohe and Rockland, 2004).…”

Zinc histochemistry reveals circuit refinement and distinguishes visual areas in the developing ferret cerebral cortex

“…Previous studies have demonstrated the use of zinc histochemistry in distinguishing cortical areas in adult mouse (Garrett et al 1991, 1994; Brown and Dyck 2004), developing and adult rat (Pérez-Clausell 1996; Valente et al 2002), and developing and adult cat (Dyck et al 1993). We demonstrate here that zinc histochemistry similarly distinguishes cortical areas in the developing ferret visual cortex.…”

Cyto- and Chemoarchitecture of the Cortex of the Tammar Wallaby <i>(Macropus</i><i>eugenii)</i>: Areal Organization

“…In particular, cytochrome oxidase (CO) activity has proved extremely useful in delineating sensory regions in comparative studies of mammalian cortex [Krubitzer, 1995], whereas acetylcholinesterase (AChE) has been useful in distinguishing cortical regions in many eutheria and metatheria [Garrett et al, 1994]. Non-phosphorylated neurofi lament protein immunoreactivity (e.g., as detected by the SMI-32 antibody) has proven to be a useful marker of projection neuron distribution in eutheria, leading to the delineation of many distinct regions in primate cortex [Carmichael and Price, 1994;Hof et al, , 1996Nimchinsky et al, 1996Nimchinsky et al, , 1997Preuss et al, 1997].…”

“…Anatomical studies of cortical organization in Macropodidae have been largely confi ned to Nissl [Mayner, 1989b;Weller, 1993], myelin staining and occasional studies of enzyme reactivity in isolated cortical regions [Garrett et al, 1994]. In diprotodontid metatheria, to date there have not been any detailed cortical chemoarchitectural studies that take advantage of an approach integrating information from Nissl staining, cytochrome oxidase, acetylcholinesterase, NADPH diaphorase and neurofi lament immunoreactivity and correlating this data with functional and connectivity data.…”