title: Comparative morphology of the substantia nigra and ventral tegmental area in the monkey, cat and rat.
abstract: Four types of neurons were identified in the substantia nigra (SN) of the monkey, cat, and rat. The compacta-type neurons, characterized by unevenly distributed and intensely stained Nissl substance, display many shapes and sizes. The reticulata-type neurons, characterized by the presence of discrete Nissl bodies, are triangular or round. The intermediary-type neurons contain less intensely stained but more diffusely distributed Nissl substance. These triangular or fusiform neurons have thinner processes than the compacta- and reticulata-type cells. The globular-type neurons, characterized by a high nuclear/cytoplasmic ratio, are much smaller than the three other types of SN neurons. The total number of neurons of the SN, which is much greater in the macaque (n=73,508) than in the cat (n=38,366) and the rat (n=22,532), is comprised mainly of the compacta type neurons (n=62,624; 22,323; and 9.925 in the three species, respectively). The reticulata-type neurons are more abundant in the cat, and the intermediary and globular types are more numerous in the rat. The compacta-type neurons have a particular distribution in each species. The ventral tegmental area (VTA) contains numerous globular-type neurons and a number of compacta-like or transitional type neurons which constitute the foyer pédiculaire of the central linear nucleus and the paranigral nucleus. The rostral linear nucleus is unique to the cat brain.
mesh_terms: D000818:Animals; D001931:Brain Mapping; D002415:Cats; D002452:Cell Count; D008253:Macaca mulatta / Q000033:anatomy & histology; D009434:Neural Pathways / Q000033:anatomy & histology; D009474:Neurons / Q000166:cytology; D051381:Rats; D013045:Species Specificity; D013378:Substantia Nigra / Q000033:anatomy & histology* / Q000166:cytology; D013681:Tegmentum Mesencephali / Q000033:anatomy & histology* / Q000166:cytology