Anat Embryol (2004) 208:239–247 DOI 10.1007/s00429-004-0395-0 ORIGINAL ARTICLE Mette Larsen · Carsten R. Bjarkam · Karen Østergaard · Mark J. West · Jens C. Sørensen The anatomy of the porcine subthalamic nucleus evaluated with immunohistochemistry and design-based stereology Accepted: 16 March 2004 / Published online: 27 May 2004  Springer-Verlag 2004 Abstract This study provides a light-microscopic de- scription of the organization, morphology and number of neurons in the subthalamic nucleus (STN) of the Göttin- gen minipig. It is based on histological material stained with Nissl, Golgi and autometallographic techniques, and employs design-based stereological estimation of the total neuron number. The organization of several neurotrans- mitters in the STN has been evaluated in histological preparations stained for acetylcholinesterase (AChE) and immunostained for choline acetyltransferase (ChAT), ty- rosine hydroxylase (TH), glutamic acid decarboxylase (GAD) and glutamate. In all of the stained preparations the STN appeared as a distinct lens-shaped structure lo- cated in the caudal diencephalon, medial to the internal capsule and ventrolateral to the zona incerta. Rostrally, the STN approached the globus pallidus pars interna, whereas caudally the ventromedial part of the STN was adjacent to the rostral part of the substantia nigra pars compacta (SNc), where some of the neurons of the two nuclei merged. The neurons in the STN had medium- sized (25–40 mm) ovoid or fusiform cell bodies, from which three to six large dendrites emanated in a direction predominantly parallel to the long axis of the STN. Im- munohistochemistry revealed that most of the subtha- lamic neurons were glutamatergic and differed signifi- cantly in appearance from the large stellate TH-positive cells of the adjacent SNc. Numerous TH-positive bouton- rich fibers traversed the STN. The GAD-staining revealed a large number of terminals within the boundaries of the STN. The STN was highly AChE-positive, reflecting a prominent innervation by ChAT-positive terminals. The total number of subthalamic neurons in one hemisphere was estimated to be approximately 56,000. We conclude that the neuroarchitecture of the porcine STN is similar to primates, including humans, and appears well-suited for further studies examining the role of the STN in move- ment disorders. Keywords Animal model · DBS · Göttingen minipig · Parkinson’s disease · STN Abbreviations AChE: Acetylcholinesterase · AMG: Autometallography · asf: Area sampling fraction · ChAT: Choline acetyltransferase · CI: Internal capsule · DBS: Deep brain stimulation · fl: Lenticular fasciculus · GAD: Glutamic acid decarboxylase · GPe: Globus pallidus pars externa · GPi: Globus pallidus pars interna · mfb: Medial forebrain bundle · MPTP: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine · nsp: Nigrostriatal pathway · SN: Substantia nigra · SNc: Substantia nigra, pars compacta · SNl: Substantia nigra, pars lateralis · ssf: Section sampling fraction · STN: Subthalamic nucleus · TBS: Tris-buffered saline · TH: Tyrosine hydroxylase · VTA: Ventral tegmental area · ZI: Zona incerta Introduction Studies performed over the last two decades have indi- cated that the subthalamic nucleus (STN) is widely im- plicated in the pathophysiology of Parkinson’s disease (PD). Accordingly, striatal dopamine depletion associated with PD may result in an increased glutamatergic output of the STN, followed by a decrease in thalamocortical motor activation (Albin et al. 1989; Alexander and Crutcher 1990; DeLong 1990; Alexander 1994; Parent M. Larsen ( ) ) · C. R. Bjarkam · M. J. West · J. C. Sørensen Department of Neurobiology, Institute of Anatomy, University of Aarhus, 8000 Aarhus C, Denmark e-mail: ml@neuro.au.dk Tel.: +45-8942-3027 Fax: +45-8942-3060 K. Østergaard Department of Neurology, University Hospital of Aarhus, 8000 Aarhus C, Denmark J. C. Sørensen Department of Neurosurgery, University Hospital of Aarhus, 8000 Aarhus C, Denmark