Localisation of Calcium Binding Proteins in the Neostriatum

Abstract

The neostriatum represents the major division of the basal ganglia and is the primary recipient of cortical information flowing into the basal ganglia. In order to understand how extrinsic information is processed and integrated with other extrinsic inputs and with local neurones to produce signals that are transmitted to the output structures of the basal ganglia, the substantia nigra and the pallidal complex, it is necessary to have detailed plans of the microcircuitry in which the morphological and chemical features, as well as the afferent and efferent connections, of each component is known. To this end, a great deal of work has already been carried out in establishing the microcircuitry of the neostriatum and the basal ganglia in general (see Smith and Bolam, 1990 for review). This work has been based on the analysis of Golgi-impregnated neurones, and more recently, on the analysis of structures immunostained to reveal either the neurotransmitter content of neurones or a neurotransmitter-related marker, for instance the synthetic enzyme or catabolic enzyme of a neurotransmitter. It is becoming increasingly apparent that antibodies against markers other than the neurotransmitter-related substances are of value in the elucidation of neural microcircuits. One such group of substances are the calcium binding proteins that are widely distributed within the central nervous system and although little is known about their functions, antibodies directed against them have been instrumental in the discovery of subpopulations of neurones within many regions of the brain (Gulyás et al., 1991; Jacobowitz and Winsky, 1991; Seress et al., 1991; Résibois and Rogers, 1992), and in the elucidation of the neuronal microcircuits to which these cells contribute (Freund and Gulyás, 1991; Gulyás et al., 1992; Miettinen et al., 1992). Within the neostriatum the calcium-binding proteins parvalbumin, calretinin and calbindin D28k have been localised in distinct subpopulations of neurones. Parvalbumin is present in a population of neurones that have been identified as the GABAergic interneurones of the striatum (Cowan et al., 1990; Kita et al., 1990) and immunoreactivity for calretinin is localised in a small population of striatal neurones (Jacobowitz and Winsky, 1991; Résibois and Rogers, 1992; Bennett and Bolam, 1993a). In contrast, the calcium-binding protein, calbindin D28k, is present in a much larger population of neurones that have the characteristics of the most common class of striatal neurone, the medium-size densely spiny neurone (Gerfen et al., 1985; Gerfen, 1992).KeywordsGABAergic InterneuronesAsymmetrical SynapseSymmetrical SynapseMatrix CompartmentStriatal InterneuronesThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.