Striatal NPY‐Containing Neurons Receive GABAergic Afferents and may also Contain GABA: An Electron Microscopic Study in the Rat

Abstract

Dual labelling methods were applied to localize simultaneously neuropeptide Y (NPY) and glutamate decarboxylase (GAD) immunoreactivities on ultrathin sections of the rat caudate-putamen (CP). By means of a double peroxidase-anti-peroxidase technique, using 3,3'-diaminobenzidine and benzidine dihydrochloride as chromogens in animals with no colchicine pretreatment, GAD immunoreactivity was found to be present in terminals only whereas NPY immunoreactivity was detected in neurons displaying the features of aspiny type cells and processes. With this approach, we observed numerous synaptic associations of the symmetrical type between GAD-immunoreactive (-Ir) axonal boutons and NPY-Ir cell bodies and dendrites. By combining immunoperoxidase and radioimmunocytochemical labelling in animals pretreated with colchicine, NPY was again detected in a single population of aspiny type neurons whereas GAD immunoreactivity was observed in neurons which could be classified as aspiny and spiny on the basis of their ultrastructural characteristics. All the cells of the aspiny type displaying clear-cut NPY immunoreactivity were also found to be GAD-positive. Some other neurons of both the aspiny and the spiny type were found to be immunoreactive to GAD alone. GAD/NPY dually labelled terminals were also observed and some axo-axonic appositions between GAD- and NPY-Ir terminals were also detected. All in all, these data show that NPY aspiny type neurons of the rat CP receive GABAergic afferents and provide morphological support for two hypotheses: that NPY is co-localized with GABA in some cell bodies, dendrites and axons, and that presynaptic interactions may occur between NPY and GABAergic neuronal systems.

Ultrastructural features of the nitric oxide synthase-containing interneurons in the nucleus accumbens and their relationship with tyrosine hydroxylase-containing terminals

“…Nevertheless, our data are comparable to the minor diameters of Dimova's medium aspiny class IV (Dimova et al, 1980) and somatostatin-containing cells of the cat dorsal striatum . Rare, spine-like protrusions on some dendrites (DiFiglia and Aronin, 1982;Vuillet et al, 1989bVuillet et al, , 1990Gracy and Pickel, 1997;Morello et al, 1997) did not broaden out or display spine apparatus, which may explain why spines are not always reported (Takagi et al, 1983;Pickel, 1988, 1989;Massari et al, 1988;Fujiyama and Masuko, 1996). Axons immunopositive for NOS were unmyelinated and their boutons did not contain dense core vesicles, unlike previous reports in the striatal NPY/somatostatin population Fig.…”

“…There is also some question as to whether, in addition to releasing neuroactive compounds such as NPY (Wahlestedt and Hakanson, 1986;Walker et al, 1988), somatostatin (McCann, 1982), or NO (Bredt et al, 1990;Garthwaite, 1991;Manzoni et al, 1992), all neurons in this subpopulation are GABAergic. Despite the fact that not all NPY-stained neurons expressed GABA (Aoki and Pickel, 1989), all were reported to contain glutamate decarboxylase (GAD) (Vuillet et al, 1990), and, although neurons resembling the NOS-containing morphologic subtype are not reported in GAD- (Kita and Kitai, 1988) or GABA- immunolabeling studies, GABA immunoreactivity has been reported in terminals of somatostatin/NOS-positive cells (unpublished observation cited in Kawaguchi et al, 1995). Furthermore, GAD immunoreactivity and NOS immunoreactivity colocalize in colchicine-treated rats (Kubota et al, 1993).…”

Regional and cellular localisation of GABAA receptor subunits in the human basal ganglia: An autoradiographic and immunohistochemical study

“…It may be that these two major types of interneurons (ChAT and NPY) contain other types of GABA A receptor subunits that were not investigated in this study. Previous ultrastructural studies on NPY/ somatostatin neurons have shown that, although there are only infrequent synaptic contacts on these neurons (DiFiglia and Aronin, 1982), some of these axon terminals have been shown to be GABA-positive (Aoki and Pickel, 1989;Vuillet et al, 1990); this would suggest that GABA may act on these interneurons through GABA A receptors that do not include ␣ 1 , ␣ 2 , ␣ 3 , ␤ 2,3 , and ␥ 2 subunits and/or GABA B receptors. The ChAT neurons on the other hand have been shown to have a large number of different types of synaptic contacts (Phelps et al, 1985;DiFiglia and Carey, 1986); these include GABAergic boutons (Bolam and Bennett, 1995) and substance P-and Enk-immunoreactive synaptic contacts (Bolam et al, 1986;Martone et al, 1994) that colocalise with GABA (Aronin et al, 1984;Penny et al, 1986;Besson et al, 1990).…”

“…Previous studies in the rat have shown that virtually all of the striatal projection neurons are GABAergic medium-sized spiny neurons that project to the globus pallidus and substantia nigra; these GABAergic projection neurons contain the calcium binding protein calbindin (Calb), and the axons of these neurons additionally provide local axon collateral terminals within the striatum (Preston et al, 1980;Wilson and Groves, 1980;Nitsch and Riesenberg, 1988;DiFiglia et al, 1989). Various types of GABAergic interneurons have also been identified in the caudate-putamen (Bolam and Bennett 1995;Kawaguchi et al, 1995); they include a variety of types of aspiny interneurons that contain the calcium binding protein parvalbumin (Parv; Cowan et al, 1990;Kita et al, 1990;Coté et al, 1991), the calcium binding protein calretinin (Calr; Bennett and Bolam 1993;Bennett and Bolam 1994c), or somatostatin/ neuropeptide Y (NPY; Vincent et al, 1983;Chesselet and Graybiel, 1986;Vuillet et al, 1990;Kubota et al, 1993;Figueredo-Cardenas et al, 1996). In addition to these various types of GABAergic neurons, the caudate-putamen also receives GABAergic afferents from the globus pallidus (Staines et al, 1981;Staines and Fibiger, 1984;Kita and Kitai, 1991;Rajakumar et al, 1994).…”

A sequential protocol combining dual neuroanatomical tract-tracing with the visualization of local circuit neurons within the striatum

“…Projections coming from the cerebral cortex, the pars compacta of the substantia nigra and the thalamus are known to synapse both on projection neurons and interneurons (Kubota et al, 1987;Vuillet et al, 1990;Dimova et al, 1993;Bennett and Bolam, 1994;Kachidian et al, 1996Kachidian et al, , 1998Smith, 1996, 1999;Koó s and Tepper, 1999;Rudkin and Sadikot, 1999). Striatal inputs may influence the striatal output through directing their contacts onto striatal projection neurons or by exciting the interneurons which synchronize the discharge of several striatal projection neurons (Koó s and Tepper, 1999).…”