title: Cyto- and chemoarchitecture of the dorsal thalamus of the monotreme Tachyglossus aculeatus, the short beaked echidna.
abstract: We have examined the cyto- and chemoarchitecture of the dorsal thalamus of the short beaked echidna (Tachyglossus aculeatus), using Nissl and myelin staining, immunoreactivity for parvalbumin, calbindin, calretinin and non-phosphorylated neurofilament protein (SMI-32 antibody), and histochemistry for acetylcholinesterase and NADPH diaphorase. Immunohistochemical methods revealed many nuclear boundaries, which were difficult to discern with Nissl staining. Parvalbumin immunoreactive somata were concentrated in the ventral posterior, reticular, posterior, lateral and medial geniculate nuclei, while parvalbumin immunoreactivity of the neuropil was present throughout all but the midline nuclei. Large numbers of calbindin immunoreactive somata were also found within the midline thalamic nuclei, and thalamic sensory relay nuclei. Immunoreactivity for calretinin was found in many small somata within the lateral geniculate "a" nucleus, with other labelled somata found in the lateral geniculate "b" nucleus, ventral posterior medial and ventral posterior lateral nuclei. Immunoreactivity with the SMI-32 antibody was largely confined to somata and neuropil within the thalamocortical relay nuclei (ventral posterior medial and lateral nuclei, lateral and medial geniculate nuclei and the posterior thalamic nucleus). In broad terms there were many similarities between the thalamus of this monotreme and that of eutheria (e.g. disposition of somatosensory thalamus, complementarity of parvalbumin and calbindin immunoreactive structures), but there were some unique features of the thalamus of the echidna. These include the relatively small size of the thalamic reticular nucleus and the preponderance of calbindin immunoreactive neurons over parvalbumin immunoreactive neurons in the ventral posterior nucleus.
authors.affiliation: Department of Anatomy, School of Medical Sciences, The University of New South Wales, NSW 2052, Australia. k.ashwell@unsw.edu.au
authors.forename: Ken W S
authors.initials: KW
authors.lastname: Ashwell
authors.forename: George
authors.initials: G
authors.lastname: Paxinos
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001306:Auditory Pathways / Q000166:cytology / Q000378:metabolism; D064032:Calbindin 2; D064026:Calbindins; D005260:Female; D005829:Geniculate Bodies / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D020645:Mediodorsal Thalamic Nucleus / Q000166:cytology / Q000378:metabolism; D020644:Midline Thalamic Nuclei / Q000166:cytology / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D019581:Neuropil / Q000378:metabolism; D010320:Parvalbumins / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013194:Staining and Labeling; D004442:Tachyglossidae / Q000033:anatomy & histology*; D013788:Thalamus / Q000166:cytology* / Q000378:metabolism; D020651:Ventral Thalamic Nuclei / Q000166:cytology / Q000378:metabolism; D014795:Visual Pathways / Q000166:cytology / Q000378:metabolism
chemical_list: D064032:Calbindin 2; D064026:Calbindins; D016900:Neurofilament Proteins; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G; D009252:NADPH Dehydrogenase; D000110:Acetylcholinesterase