Double retrograde tracer study of the thalamostriatal projections to the cat caudate nucleus

Abstract

The distribution of thalamostriatal neurons projecting to the cat caudate nucleus was examined by retrograde fluorescent tracers. Thus, Fast Blue and Diamidino Yellow were concomitantly injected in different rostrocaudal, dorsoventral, or mediolateral sectors of the caudate nucleus. The main findings of this study are as follows: (1) few double-labeled cells were found after two injections in different sectors of the caudate nucleus; (2) double-labeled neurons were more abundant after adjacent injections and they were mainly located in the caudal intralaminar nuclei, in the rhomboid nucleus and in the dorsal mediodorsal nucleus; and (3) there were variations in the spatial organization of the thalamostriatal neurons projecting to various sectors of the caudate nucleus in the different thalamic nuclei known to project to this part of the striatum.

Thalamic interaction between the input and the output systems of the basal ganglia

“…2A%-B% and de las Heras et al, 1998b;Erro et al, 1998). Contrarily to the widespread distribution pattern observed in the ventral nuclei, the thalamostriatal cells within the rostral intralaminar nuclei were arranged in dense clusters (Parent et al, 1983;de las Heras et al, 1998bde las Heras et al, , 1999 and when two retrograde tracers were used, the clusters containing one tracer were intermingled with the ones containing the other. This arrangement suggests a possible modular organization of this projection.…”

“…Remarkably, no double-labeled neurons could be found in any of these nuclei after two fluorescent tracer deposits in different rostrocaudal, dorsoventral or mediolateral regions of the cat caudate nucleus or after putamen vs. caudate nucleus deposits in the squirrel monkey (Fig. 2, for methodological considerations see de las Heras et al, 1999; see also Parent et al, 1983;de las Heras et al, 1997de las Heras et al, , 1998ade las Heras et al, , 1999. This may indicate the high specificity of the topographical thalamostriatal projections arising from the subdivisions of the ventral nuclei, which is emphasized by the high degree of segregation displayed by the motor-related subcortical afferents to these subdivisions (see Section 3).…”

“…These neurons do collateralize within the striatum, as revealed by the presence of double-labeled neurons, although their number is very low (Fig. 2 and Parent et al, 1983;de las Heras et al, 1999). Such collateralization occurs both in the mediolateral and rostrocaudal coordinates but not in the dorsoventral coordinate in the cat striatum (de las Heras et al, 1999).…”

“…2 and Parent et al, 1983;de las Heras et al, 1999). Such collateralization occurs both in the mediolateral and rostrocaudal coordinates but not in the dorsoventral coordinate in the cat striatum (de las Heras et al, 1999). Remarkably enough, the double-labeled neurons tend to be localized at the transitional areas between the two single labeled populations ( Fig.…”

“…Thus, thalamic neurons in the ventral nuclei (ventral anterior, ventral lateral and ventral medial thalamic nuclei) are retrogradely labeled almost exclusively after rostral injections in the rostral caudate nucleus, that is, they almost exclusively project to rostral striatal areas (Tanaka et al, 1986;Erro et al, 1998;de las Heras et al, 1998bde las Heras et al, , 1999. Within these Fig.…”