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. DTN contains a dense population of GABAergic cells. In the rat, few also express

calbindin Calbindins are three different calcium-binding proteins: calbindin, calretinin and S100G. They were originally described as vitamin D-dependent calcium-binding proteins in the intestine and kidney in the chick and mammals. They are now classified ...

(CB) or

calretinin Calretinin, also known as calbindin 2 (formerly 29 kDa calbindin), is a calcium-binding protein involved in calcium signaling. In humans, the calretinin protein is encoded by the ''CALB2'' gene. Function This gene encodes an intracellular ca ...

(CR). Many of the DTN GABAergic cells do express

parvalbumin Parvalbumin (PV) is a calcium-binding protein with low molecular weight (typically 9-11 kDa). In humans, it is encoded by the ''PVALB'' gene. It is not a member of the albumin family; it is named for its size (''parv-'', from Latin ''parvus'' smal ...

(PV) with the densest expression in the pars ventralis portion. DTN neurons in rats contain small number of

neuropeptide Y Neuropeptide Y (NPY) is a 36 amino-acid neuropeptide that is involved in various physiological and homeostatic processes in both the central and peripheral nervous systems. NPY has been identified as the most abundant peptide present in the ma ...

positive (NPY) neurons implicating a role in hunger and feeding. In rats, the DTN contains a small number of

enkephalin An enkephalin is a pentapeptide involved in regulating nociception in the body. The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin ...

substance p Substance P (SP) is an undecapeptide (a peptide composed of a chain of 11 amino acid residues) and a member of the tachykinin neuropeptide family. It is a neuropeptide, acting as a neurotransmitter and as a neuromodulator. Substance P and its clos ...

, and glutamatergic neurons which project to mammillary.

Circuitry

As part of the Papez circuit, the DTN receives input from habenula neurons and lateral mammillary neurons. DTN especially the central part of the DTN receives projections from the G-protein coupled receptor GPR151 containing habenula neurons. The pars centralis of the DTN receives input from the prepositus hypoglossi and the supragenualis nucleus. 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

Projections

Dorsal tegmental fibres project to * lateral mammillary neurons (LMN) * dorsal noradrenergic bundle * 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 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. Subpopulations of DTN neurons respond differently to changes in angular head velocity (AHV) and head direction (HD). {{cite journal, vauthors=Bassett JP, Tullman ML, Taube JS, title=Lesions of the tegmentomammillary circuit in the head direction system disrupt the head direction signal in the anterior thalamus. , journal=J Neurosci , year= 2007 , volume= 27 , issue= 28 , pages= 7564–77 , pmid=17626218 , pmc=6672597, doi=10.1523/JNEUROSCI.0268-07.2007 , doi-access=free 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

Brainstem Neuroanatomy