Neuroanatomical study of afferent projections to the supramammillary nucleus of the rat

Abstract

We examined the regions projecting to the supramammillary nucleus of the rat with retrograde transport of WGA-HRP and WGA, and anterograde transport of Phaseolus vulgaris leucoagglutinin. The supramammillary nucleus receives major descending afferents from the infralimbic cortex, the dorsal peduncular cortex, the nucleus of the diagonal band of Broca, the medial and lateral preoptic nuclei, bilaterally. The major ascending afferents come from the pars compacta of the nucleus centralis superior, the ventral tegmental nucleus, and the laterodorsal tegmental nucleus. The supramammillary nucleus also receives a few (but distinct) fibers from the anterior and lateral hypothalamic nuclei, the ventral premammillary nucleus, the interpeduncular nucleus, the cuneiform nucleus, the dorsal raphe nucleus, the incertus nucleus, and the C3 region including the prepositus hypoglossi nucleus. All descending fibers run through the medial forebrain bundle. Almost all ascending fibers from the pars compacta of the nucleus centralis superior and the laterodorsal tegmental nucleus run through the mammillary peduncle, and terminate throughout the supramammillary nucleus. A few fibers from the laterodorsal tegmental nucleus and the C3 region run through the fasciculus longitudinalis dorsalis and terminate in the dorsal part of the supramammillary nucleus including the supramammillary decussation.

Similar effects of medial supramammillary or systemic injection of chlordiazepoxide on both theta frequency and fixed-interval responding

“…Procaine in the mSuM itself reduced both the frequency and amplitude of theta. A transduction role for the mSuM of brainstem impulses bound for the medial septum is consistent with tracing studies that have identified projections to the mSuM from the RPO (Vertes & Martin, 1988) and other brainstem structures (Hayakawa, Ito, & Zyo, 1993) and from the mSuM to the medial septum via the median forebrain bundle (Borhegyi, Magloczky, Acsady, & Freund, 1998;Shepard, Mihailoff, & German, 1988;Vertes, 1988Vertes, , 1992.…”

Synaptic organization of afferent projections to the supramammillary nucleus of the rat

“…There are reciprocal connections between the SUM and the preoptic area, the diagonal band nucleus, and the laterodorsal tegmental nucleus at the light microscopic level (Swanson 1982;Satoh and Fibiger 1986;Vertes 1992;Hayakawa et al 1993). The present study suggests that they exist at the ultrastructural level, except in the case of the laterodorsal tegmental nucleus.…”

“…Our findings agree with theirs concerning the morphology of terminals from the infralimbic cortex. Our previous study using anter0grade tracing with Phaseolus vulgaris leucoagglutinin (Hayakawa et al 1993) showed that afferent projections from the infralimbic cortex were confined to the ventral region of the SUM. Infralimbic cortical neurons may contact dopaminergic neurons in the SUM as well as in the ventral tegmental area.…”

“…In return, the SUM receives afferent fibers mainly from the infralimbic cortex, including the dorsal peduncular cortex (Sesack et al 1989;Hurley et al 1991), the nucleus of the diagonal band of Broca , the medial and lateral preoptic nuclei (Swanson 1976;Simerly and Swanson 1988), the central superior nucleus and the laterodorsal tegmental nucleus (Hayakawa et al 1993). Although no direct synaptic contacts from these nuclei have been studied, the SUM is thought to play an important role in locomotor activity, ingestive behavior and activity of limbic forebrain structures similar to the ventral tegmental area of Tsai (Pijnenbnrg et al 1976;Swanson and Mogenson 1981).…”

Fine structure of the supramammillary nucleus of the rat: Analysis of the ultrastructural character of dopaminergic neurons

“…The SUM projects to the cingulate cortex, the infralimbic cortex, the entorhinal cortex, the septal nuclei, the hippocampus, the preoptic area, and the midbrain tegmentum (Wyss et al, 1979;Veazey et al, 1982;Haglund et al, 1984;Vertes, 1992). The major afferent fibers come from the infralimbic cortex, the septal nuclei, the preoptic area, and the laterodorsal tegmental nucleus (Swanson, 1976;Swanson and Cowan, 1979;Sesack et al, 1989;Satoh and Fibiger, 1986;Hurley et al, 1991;Hayakawa et al, 1993). Many cholinergic fibers are present in the SUM (Ruggiero et al, 1990).…”