Biology:Dorsal tegmental nucleus

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The dorsal tegmental nucleus (DTN), also known as dorsal tegmental nucleus of Gudden (DTg), is a group of neurons located in the brain stem, which are involved in spatial navigation and orientation.

Anatomy

The dorsal tegmental nucleus is located in the brain stem near the midline. Two nuclei exist in both hemispheres. The DTN is generally subdivided into four parts called partes centralis, ventromedialis, anterior, and posterior.[1]

DTN contains a dense population of GABAergic cells.[2][3] In the rat, few also express calbindin (CB) or calretinin (CR). Many of the DTN GABAergic cells do express parvalbumin (PV) with the densest expression in the pars ventralis portion.[4][5] DTN neurons in rats contain small number of neuropeptide Y positive (NPY) neurons implicating a role in hunger and feeding. In rats, the DTN contains a small number of enkephalin, substance p, and glutamatergic neurons which project to mammillary.[6]

Circuitry

As part of the Papez circuit, the DTN receives input from habenula neurons [1] and lateral mammillary neurons.[7] DTN especially the central part of the DTN receives projections from the G-protein coupled receptor GPR151 containing habenula neurons.[8]

The pars centralis of the DTN receives input from the prepositus hypoglossi and the supragenualis nucleus.[9] Pars ventromedialis of the DTN receives inputs from

  • the septal nuclei,
  • diagonal band of Broca,
  • preoptic area,
  • anterior and lateral hypothalamus,
  • lateral and medial habenular nuclei,
  • medial mammillary nucleus and
  • brainstem reticular formation [9]

Projections

Dorsal tegmental fibres project to

  • lateral mammillary neurons (LMN) [4][2][3][5]
  • dorsal noradrenergic bundle [10]
  • nuclei medialis profundus
  • centralis superior,
  • the tegmental reticular nucleus,
  • the ventral tegmental area of Tsai, and
  • the posterior hypothalamic nucleus. The nucleus is a major synaptic station for the pathways of the dorsal longitudinal fasciculus between the diencephalon and lower brain stem [11]

DTN is a major source of fibers in the mammillary peduncle. Rostral DTN cells that project to the LMN are localized within pars dorsalis and caudal cells that project to the LMN are located in the pars ventralis.

Function

This nucleus is involved in landmark and directional navigation.[12] Subpopulations of DTN neurons respond differently to changes in angular head velocity (AHV) and head direction (HD).[13][14][15][16] Some cells respond to changes in head movement in specific directions such as to the left, right, or both. The firing activity of these cells are also affected by the speed of the movement of the head as well. DTN lesions permanently impaired landmark navigation, but only transiently impaired directional navigation.


References

  1. ↑ 1.0 1.1 "Efferent connections of the habenular nuclei in the rat.". J Comp Neurol 187 (1): 19–47. 1979. doi:10.1002/cne.901870103. PMID 226566. https://pubmed.ncbi.nlm.nih.gov/226566. 
  2. ↑ 2.0 2.1 "Mamillary body in the rat: topography and synaptology of projections from the subicular complex, prefrontal cortex, and midbrain tegmentum.". J Comp Neurol 286 (3): 311–36. 1989. doi:10.1002/cne.902860303. PMID 2504784. https://pubmed.ncbi.nlm.nih.gov/2504784. 
  3. ↑ 3.0 3.1 "Evidence for GABAergic projections from the tegmental nuclei of Gudden to the mammillary body in the rat.". Brain Res 630 (1–2): 188–94. 1993. doi:10.1016/0006-8993(93)90656-8. PMID 8118685. https://pubmed.ncbi.nlm.nih.gov/8118685. 
  4. ↑ 4.0 4.1 "Calcium-binding protein immunoreactivity in Gudden's tegmental nuclei and the hippocampal formation: differential co-localization in neurons projecting to the mammillary bodies.". Front Neuroanat 9: 103. 2015. doi:10.3389/fnana.2015.00103. PMID 26300741. 
  5. ↑ 5.0 5.1 "Projections from Gudden's tegmental nuclei to the mammillary body region in the cynomolgus monkey (Macaca fascicularis).". J Comp Neurol 520 (6): 1128–45. 2012. doi:10.1002/cne.22740. PMID 21830220. 
  6. ↑ "Localization of amino acids, neuropeptides and cholinergic neurotransmitter markers in identified projections from the mesencephalic tegmentum to the mammillary nuclei of the rat.". J Chem Neuroanat 16 (2): 117–33. 1999. doi:10.1016/s0891-0618(98)00063-5. PMID 10223311. https://pubmed.ncbi.nlm.nih.gov/10223311. 
  7. ↑ "Quantitative and ultrastructural study of ascending projections to the medial mammillary nucleus in the rat.". Anat Embryol (Berl) 184 (6): 611–22. 1991. doi:10.1007/bf00942583. PMID 1776707. https://pubmed.ncbi.nlm.nih.gov/1776707. 
  8. ↑ "Conserved expression of the GPR151 receptor in habenular axonal projections of vertebrates.". J Comp Neurol 523 (3): 359–80. 2015. doi:10.1002/cne.23664. PMID 25116430. 
  9. ↑ 9.0 9.1 "The dorsal tegmental nucleus: an axoplasmic transport study.". Brain Res 310 (1): 123–32. 1984. doi:10.1016/0006-8993(84)90015-5. PMID 6434154. https://pubmed.ncbi.nlm.nih.gov/6434154. 
  10. ↑ "Electrophysiological identification of neurons in locus coeruleus.". Exp Neurol 53 (1): 254–66. 1976. doi:10.1016/0014-4886(76)90295-8. PMID 964341. https://pubmed.ncbi.nlm.nih.gov/964341. 
  11. ↑ MOREST DK (1961). "Connexions of the dorsal tegmental nucleus in rat and rabbit.". J Anat 95 (Pt 2): 229–46. PMID 13772534. 
  12. ↑ "Lesions of the dorsal tegmental nuclei disrupt control of navigation by distal landmarks in cued, directional, and place variants of the Morris water task.". Behav Neurosci 127 (4): 566–81. 2013. doi:10.1037/a0033087. PMID 23731069. 
  13. ↑ "Neural correlates for angular head velocity in the rat dorsal tegmental nucleus.". J Neurosci 21 (15): 5740–51. 2001. doi:10.1523/jneurosci.21-15-05740.2001. PMID 11466446. 
  14. ↑ "Angular velocity and head direction signals recorded from the dorsal tegmental nucleus of gudden in the rat: implications for path integration in the head direction cell circuit.". Behav Neurosci 115 (3): 571–88. 2001. doi:10.1037/0735-7044.115.3.571. PMID 11439447. https://pubmed.ncbi.nlm.nih.gov/11439447. 
  15. ↑ Taube JS (2007). "The head direction signal: origins and sensory-motor integration.". Annu Rev Neurosci 30: 181–207. doi:10.1146/annurev.neuro.29.051605.112854. PMID 17341158. https://pubmed.ncbi.nlm.nih.gov/17341158. 
  16. ↑ "Lesions of the tegmentomammillary circuit in the head direction system disrupt the head direction signal in the anterior thalamus.". J Neurosci 27 (28): 7564–77. 2007. doi:10.1523/JNEUROSCI.0268-07.2007. PMID 17626218. 



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