Limbic projections to the cat thalamus A horseradish peroxidase study Gy. Somogyi, F. Hajdu, T. Tombol and M. Madarasz First Department of Anatomy, Faculty of Medicine, Semmelweis University, Budapest, Hungary
Key words. Anterior thalamic nuclei • HRP method • Cat Abstract. Retrograde axonal transport of horseradish peroxidase was used to identify the afferent projection systems of the anterior thalamic nuclei in the cat. The results indicate that fibres projecting to the three anterior nuclei of the thalamus arise from the hippocampal region, septum and cingulate cortex unilaterally and from the hypothalamus (mamillary nuclei) both bilaterally and unilaterally. The cells of the medial mamillary nuclei send their axons to the ipsilateral AV and AM nuclei whereas the lateral mamillary nucleus projects bilaterally to the AD nuclei.
The connections of the anterior thalamic nuclei have been studied in rat [Nama. 1956; Raisman. 1966: Homesick. 1969, 1972; Beckstead. 1976: Dekker and Kuypers, 1976; Swanson and Cowan, 1977], cat [Powell. 1966; Siegel and Tassoni, 1971: Powell et at., 1974] and monkey [Powell, 1973] using retrograde degeneration methods and, recently, axonal transport methods. However, these results arc rather controversial. The limbo-thalamic relationship in particular has received much more attention in the rat than in the cat. The diversity of data could be explained by the lack of an adequate technique. The horseradisch peroxidase (HRP) method seemed to be a suitable means to clarify the limbic connections to the cat thalamus.
iMatcrials and methods Experiments were performed in 9 adult cats. Using sterile procedures, 0.2-0.6/