+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Extended projections induced by partial de afferentiation of the medial mammillary nucleus

, : Extended projections induced by partial de afferentiation of the medial mammillary nucleus. Brain Research 188(2): 347-356

Quantitative EM of degeneration was used to study the pattern of distribution of projection fibers from the hippocampal complex to the posterior part of the medial mammillary nucleus (MMp) in rats. Two days after bilateral destruction of the fornix column almost 20% of the presynaptic terminals showed electron dense degeneration. These terminals were evenly distributed across the midline and filled the entire mediolateral and dorsoventral extent of the nucleus on both sides. Unilateral fornix lesions gave the same distribution of degeneration as bilateral lesions but with half the overall density of synapses. The overall hippocampal projection through the fornix column is formed by the coalescence of 2 separate fiber contingents which initially run through the dorsal fornix and the fimbria. Bilateral lesions of the dorsal fornix caused degeneration throughout the mediolateral extent of the MMp, but predominantly in its dorsal half. Bilateral fimbrial lesions gave a complementary pattern of degeneration, which filled the ventral half of the nucleus throughout its mediolateral extent. Unilateral fimbrial lesions gave a distribution of degeneration similar to bilateral lesions, although with about half the density of terminals. Lesions were placed bilaterally in either the dorsal fornix or the fimbria, and a survival time of 3-4 mo. allowed. This was sufficient for all the degeneration to be removed. Two days before sacrifice the remaining tract was destroyed bilaterally. In both cases the previous lesion caused the remaining tract to acquire approximately double its normal number of terminals, and to extend its distribution into the territory denervated by the first lesion. After prior fimbrial lesions the dorsal fornix fibers extended ventrally from their normal territory and established synaptic terminals virtually as far as the ventral margin of the nucleus. After prior dorsal fornix lesions the fimbrial fibers extended their terminal distribution dorsally as far as the dorsal margin of the nucleus, although the newly acquired terminals formed in the denervated territory were neither as numerous nor as evenly distributed as those in the original fimbrial territory. Denervation seemed to induce sprouting, but the efficiency of reclamation of the denervated postsynaptic sites is apparently limited, probably by competition from other axonal systems in the region.

Accession: 005432653

PMID: 6768422

Submit PDF Full Text: Here

Submit PDF Full Text

No spam - Every submission is manually reviewed

Due to poor quality, we do not accept files from Researchgate

Submitted PDF Full Texts will always be free for everyone
(We only charge for PDFs that we need to acquire)

Select a PDF file:

Related references

Beech, J.N.; Raisman, G., 1980: Extended projections induced by partial deafferentation of the medial mammillary nucleus. Brain Research 188(2): 347-355

Hayakawa T.; Zyo K., 1991: Quantitative and ultrastructural study of ascending projections to the medial mammillary nucleus in the rat. We analyzed the termination pattern of axons from the superior central nucleus and the ventral tegmental nucleus of Gudden within the medial mammillary nucleus (MM) in the rat. The neuropil of the MM consists of two classes of terminals, that is,...

Thinschmidt, J.S.; Crane, A.M.; Panickar, K.S.; Vertes, R.P., 1994: Brainstem projections to the supramammillary nucleus and medial mammillary body A WGA-HRP tracing study. Society for Neuroscience Abstracts 20(1-2): 1586

Furlani, V.C.G.; Bittencourt, J.C., 1993: Diencephalic origins of melanin-concentrating hormone immunoreactive projections to the lateral part of the medial mammillary nucleus. Society for Neuroscience Abstracts 19(1-3): 1443

Tsuchiya, R.; Takahashi, K.; Liu, F-Chin.; Takahashi, H., 2009: Aberrant axonal projections from mammillary bodies in Pax6 mutant mice: possible roles of Netrin-1 and Slit 2 in mammillary projections. Early events in the axonal tract formation from mammillary bodies remain poorly understood. In the present study, we reported an aberrant pattern of axonal projections from mammillary bodies to the dorsal thalamus in mice lacking the transcription...

Guison, N.G.; Ahmed, A.K.; Dong, K.; Yamadori, T., 1995: Projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus in the rat. There has been an abundance of research on the connections of the mammillary bodies but the projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus has remained a gray area due to a dearth of material which directly ad...

Gorbachevskaya A.I., 1972: Projections of the medial dorsal nucleus and the medial center of the thalamus to different parts of the caudate nucleus. Arkhiv Anatomii Gistologii I Embriologii: 15-22

Batton R.R., 1975: The medial mammillary nucleus of the cat a morphometric analysis. Anatomical Record 181(2): 309

Hayakawa T.; Zyo K., 1992: Ultrastructural study of ascending projections to the lateral mammillary nucleus of the rat. We examined the synaptic organization of ascending projections from the pars ventralis of the dorsal tegmental nucleus of Gudden (TDV) and the laterodorsal tegmental nucleus to the lateral mammillary nucleus (LM). The LM neuropil consists of termi...

Chen, S.T.; Wang, J.P.; Shen, C.L., 1989: Retinal projections to the medial terminal nucleus of the rat with induced unilateral congenital eye defects. Retinal projections, particularly the ipsilateral projections, to the medial terminal nucleus (MTN) of the accessory optic system were investigated by autoradiography in adult rats after being reared in one of three different conditions: (1) norma...