Striatal interneurons

All authors, beginning with Kolliker and his observations on the human striatum (Kolliker 1896), have described an aspiny neuron with a large cell body and radiating, sparsely branched dendrites. Kolliker reported that this cell had a short axon, but it was 

Although it is clear that acetylcholine release is important to striatal function the neuroanatomical substrates by which this is regulated have been difficult to clearly identify. One possible mechanism involves the reported increase in acetylcholine medi- 

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ACh is released from the large non-spiny striatal interneurons (Fig. 15.10) which only represent some 5% of total striatal neuron number. Since ACh is excitatory and DA inhibitory on striatal neurons, various schemes have been proposed to balance their antagonistic action but the role of ACh in striatal function (and PD) appears to be relatively minor. 

Kawaguchi, Y, Wilson, CJ, Augood, ST and Emson, PC (1995) Striatal interneurones chemical physiological and morphological characterization. Trends Neurosci. 18 527-535. 

GABA is the predominant intrinsic transmitter of the basal ganglia. Inhibition and disinhibition are considered to be the most important modes of information transfer in the basal ganglia. Ninety-five percent of all neurons in the striatum are GABAergic medium spiny neurons. These neurons are the striatal output neurons. The medium spiny neurons which give rise to the direct pathway also contain substance P or dynorphin as a co-transmitter, while those striatal output neurons that give rise to the indirect pathway contain enkephalin as a co-transmitter. Most striatal interneurons, as well as neurons in GPe, GPi and SNr are also GABAergic. Because striatal and GPe... 

Dopamine is a catecholamine (see Chapter 10 and Fig. 31.2) whose actions are mediated by dopamine receptors that are classified as Dj-like (Dj, D5) or D2-like (D2, D3, D4). Dopamine actions on Dj receptors exert an excitatory effect, whereas the actions of dopamine on D2 receptors inhibit neuronal activity. The loss of striatal dopamine produces an imbalance in information processing in the neostriatum that modifies transmission in other basal ganglia regions. Also important in neural transmission are the striatal interneurons that are found within the confines of the striatum, that use the excitatory neurotransmitter acetylcholine, and that modulate the activity of striatal output neurons. 

Vinar O, Klein DE, Potter WZ, et al A survey of psychotropic medications not available in the United States. Neuropsychopharmacology 5 201-217, 1991 Vitiello B, Spreat S, Behar D Obsessive-compulsive disorder in mentally retarded patients. J Nerv Ment Dis 177 232-236, 1989 Vitiello B, Shimon H, Behar D, et al Platelet imipramine binding and serotonin uptake in OCD patients. Acta Psychiatr Scand 84 29-32, 1991 Vizi ES, Harsing LG, Zsilla G Evidence of the modulatory role of serotonin in acetylcholine release from striatal interneurones. Brain Res 212 89-99, 1981 Vogel GW A review of REM sleep deprivation. Arch Gen Psychiatry 32 749-761, 1975... 

Takasawa K, Kitagawa K, Yagita Y, Sasaki T, Tanaka S, Matsushita K, Ohstuki T, Miyata T, Okano H, Hori M, Matsumoto M (2002) Increased proliferation of neural progenitor cells but reduced survival of newborn cells in the contralateral hippocampus after focal cerebral ischemia in rats. J Cereb Blood Flow Metab 22 299-307 Tanaka R, Yamashiro K, Mochizuki H, Cho N, Onodera M, Mizuno Y, Urabe T (2004) Neurogenesis after transient global ischemia in the adult hippocampus visualized by improved retroviral vector. Stroke 35 1454-1459 Teramoto T, Qiu J, Plunder JC, Moskowitz MA (2003) EGF amplifies the replacement of parvalbumin-expressing striatal interneurons after ischemia. J Clin Invest 111 1125-1132... 

Teramoto, T., Qiu, J., Plumier, J. C., and Moskowitz, M. A. (2003). EGF amplifies the replacement of parvalbumin-expressing striatal interneurons after ischemia. J. Clin. Invest. Ill, 1125-1 132. 

Centonze D, Grande C, Usiello A, Gubellini P, Erbs E, et al. 2003. Receptor subtypes involved in the presynaptic and postsynaptic actions of dopamine on striatal interneurons. 

Spiny projection neurons receive inputs from the cortex, thalamus and amygdala, which make asymmetric synapses on dendritic spines, and to a lesser degree, dendritic shafts. These inputs provide the major excitatory input to these neurons. In addition, a number of inputs from outside the striatum, and from within the striatum provide inputs that function to modify the responsiveness of spiny neurons to the excitatory input. These include inputs from dopamine afferents from the substantia nigra, inhibitory GABA inputs from the axon collaterals of other spiny neurons, inhibitory inputs from GABA (and peptide containing) striatal interneurons, and inputs from cholinergic striatal interneurons. 

Fig. 9. Summary of the major synaptic inputs to spiny projection neurons. Inputs to the cell bod> arise mainly from striatal intemeurons. Inputs to proximal dendrites are mainly from striatal interneurons and other spiny projection neurons. Inputs to distal dendrites arise from extrastriatal sources, from the cortex (asymmetric/ glutamatergic) to the spine heads, from dopamine neurons in the midbrain (symmetric/dopamine) to the necks of spines and to interspine shafts. Other spiny projection neurons also provide symmetric inputs to the necks of spines and to interspine shafts.

A third type of aspiny striatal interneuron is identified by its immunocytochemical labeling with somatostatin, neuropeptide Y, and NADPH diaphorase. These cells have also been shown to be distinguishable from parvalbumin/GABA interneurons on the basis of morphological and physiological criteria (Kawaguchi 1993). Somatostatin positive synapses are formed mainly on shafts of dendrites and dendritic spines of spiny neurons (Takagi et al. 1983). As before, all the spines involved in this connection receive another asymmetrical synaptic contact. 

Fig. II. A) Diagram of a medium aspiny striatal interneuron that had been intracellularly filled with biocytin. B) Distribution of the two major types of non-cholinergic striatal interneurons, parvalbumin-immunoreactive (IR, black dots) and somatostatin-immunoreactive (IR-white dots), in a coronal section of the striatum relative to the patch compartment. Of note is the greater number of parvalbumin containing neurons in the dorsolateral striatum compared to the ventromedial striatum and the converse pattern of somatostatin containing neurons. Drawing of medium aspiny neuron provided by H. Kita.

Marin, O., Anderson, S.A., Rubenstein, J.L. 2000. Origin and molecular specification of striatal interneurons. J. Neurosci. 20, 6063-6076. 

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