Parvalbumin and GABA in the developing somatosensory thalamus of the rat: an immunocytochemical ultrastructural correlation

Abstract

The calcium binding protein parvalbumin (PV) is widely distributed in the mammalian nervous system and its relationship with GABAergic neurons differs within thalamic nuclei and animal species. In the rat somatosensory thalamus PV immunoreactive (ir) neurons were found only in the GABAergic reticular thalamic nucleus (RT), while a dense PVir neuropil is present in the ventrobasal complex (VB). In this study the distribution and relationship of PV and GABA were investigated in RT and VB during postnatal development at electron microscopic level. The pre-embedding immunoperoxidase detection of PV was combined with the post-embedding immunogold localization of GABA. In RT, at all developmental ages, neuronal cell bodies, dendrites and rare axonal terminals were both PVir and GABAir. In VB during the first postnatal week several small vesicle-containing profiles were double-labelled and some of them were identifiable as synaptic terminals. From postnatal day 7 (P7) to P9 the medial part of VB was more intensely PVir than the lateral one and some differences in the sequence of maturation of PVir terminals were noted between these two VB subdivisions. Single-labelled PVir profiles were first observed at P8, whereas single-labelled PVir terminals appeared at P12 and at P15 they became more frequent and larger, showing the typical morphology of ascending afferents described in adult VB. These results demonstrate the late expression of PV and acquisition of adult morphology in ascending terminals of rat VB during postnatal development in comparison with the innervation arising from the GABAergic RT.

GABAergic parvalbumin-immunoreactive large calyciform presynaptic complexes in the reticular nucleus of the rat thalamus

“…Unfortunately, the fine structure of these GABA-IR structures was not studied electron microscopically; thus their cytological identity could not be established. On the other hand, according to Amadeo et al (2001) neurons of RTN are PV-and GABA-IR at all developmental ages of the rat. Furthermore, ''PV-positive cell bodies often showed several somatic protrusions, sometimes surrounding unlabelled vesicle-containing profiles or receiving presynaptically convex synaptic contacts from small terminals'' (Amadeo et al, 2001).…”

“…On the other hand, according to Amadeo et al (2001) neurons of RTN are PV-and GABA-IR at all developmental ages of the rat. Furthermore, ''PV-positive cell bodies often showed several somatic protrusions, sometimes surrounding unlabelled vesicle-containing profiles or receiving presynaptically convex synaptic contacts from small terminals'' (Amadeo et al, 2001). In our opinion, the ''somatic protrusions'' may be identical with the cellular ''necks'' from which there emerged the presynaptic calyciform complexes exhibiting PV-IR and GABA-IR, as described in this paper.…”

Early Development of the Thalamic Inhibitory Feedback Loop in the Primary Somatosensory System of the Newborn Mice

“…The nRT contains an homogeneous population of GABAergic parvalbuminpositive interneurons, and the nVPM receives a dense GABAergic projection from the nRT (Amadeo et al, 2001;Tamamaki et al, 2003), identifying the nRT-to-nVPM synapses as the connection mediating the monosynaptic unitary GABA A R-mediated IPSC we recorded in nVPM (Fig. 7).…”

Fine structural localization of connexin‐36 immunoreactivity in mouse cerebral cortex and thalamus

“…To determine the chemical features of cortical and thalamic neurons expressing Cx36 protein, we examined the colocalization of Cx36 and parvalbumin, a specific neuronal marker for inhibitory neurons in cortex and in the RTN (Hendry et al, 1989;Kawaguchi and Kubota, 1993;Amadeo et al, 2001;Galarreta and Hestrin, 2002). In the somatosensory cortex, approximately 60% of parvalbuminimmunolabeled neurons colocalized Cx36 immunoreactivity; neurons and many smaller profiles in the neuropil of layer IV of the barrel cortex were strongly double labeled (Fig.…”