The interpeduncular nucleus (IPN) is an unpaired, ovoid cell group at the base of the
midbrain tegmentum. It is located in the
mesencephalon below the
interpeduncular fossa. As the name suggests, the interpeduncular nucleus lies ''in between'' the
cerebral peduncle
The cerebral peduncles are the two stalks that attach the cerebrum to the brainstem. They are structures at the front of the midbrain which arise from the ventral pons and contain the large ascending (sensory) and descending (motor) nerve tract ...
s.
Composition
The Interpeduncular nucleus is primarily
GABAergic
In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter GABA. For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic neuron produces GABA. A ...
and contains at least two neuron clusters of different morphologies.
The region is divided into 7 paired and unpaired subnuclei
Subdivisions
The presence of non-homologous subdivisions of the Interpeduncular nucleus was first noticed by
Cajal over a hundred years ago. The currently recognized standard subdivision notation was mostly established by Hammill and Lenn in 1984 by combining the work and notations of four groups.
Although most of their proposed convention stuck, at some point the proposed "rostral lateral" sub-nucleus was renamed "dorsomedial" and became immortalized in brain atlases.
* Apical sub-nucleus (IPA)
Unpaired sub-nucleus. Former names include: "caudal dorsal", "dorsal", and "pars dorsalis magnocellularis".
* Central sub-nucleus (IPC)
Unpaired sub-nucleus. Former names include: "rostral ventral", "caudal central", "posterior inter", and "pars medianus".
* Dorsolateral sub-nucleus (IPDL)
Paired sub-nucleus.
* Dorsomedial sub-nucleus (IPDM)
Paired sub-nucleus. Former names include: "rostral lateral" and "interstitial".
* Intermediate sub-nucleus (IPI)
Paired sub-nucleus. Former names include: "caudal intermediate", "posterior inner" and "pars medianus".
* Lateral sub-nucleus (IPL)
Paired sub-nucleus. Former names include: "caudal lateral", "paramedian" and "pars lateralis".
* Rostral sub-nucleus (IPR)
Unpaired sub-nucleus. Former names include: "central" and "pars dorsalis".
Inputs
The major input to the IPN arrives via the fasciculus retroflex from the
medial habenula
In neuroanatomy, habenula (diminutive of Latin ''habena'' meaning rein) originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which th ...
. This pathway presents the IPN with several excitatory neurotransmitters including
ACh and
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 clo ...
. Other brain regions that project to the Interpeduncular nucleus include: the
Nucleus of diagonal band, the dorsal
Tegmentum
The tegmentum (from Latin for "covering") is a general area within the brainstem. The tegmentum is the ventral part of the midbrain and the tectum is the dorsal part of the midbrain. It is located between the ventricular system and distinctive ba ...
, the
Raphe nuclei, the
Central grey, and the
Locus coeruleus
The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system.
The locus coer ...
.
Outputs
The major output pathways are inhibitory and project to the dorsal Tegmental area, the
Periaqueductal gray
The periaqueductal gray (PAG, also known as the central gray) is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for d ...
and also the
Raphe nuclei. In addition, output is sent to the following: the mediodorsal nucleus of the
Thalamus
The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all direct ...
, the
lateral Habenula
In neuroanatomy, habenula (diminutive of Latin ''habena'' meaning rein) originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the ...
, the
Septal nuclei
The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum.
The septal nuclei are loc ...
, the anterior
Mammillary nuclei, the
Nucleus of diagonal band, the
Preoptic area
The preoptic area is a region of the hypothalamus. MeSH classifies it as part of the anterior hypothalamus. TA lists four nuclei in this region, (medial, median, lateral, and periventricular).
Functions
The preoptic area is responsible for ther ...
, the
Ventral tegmental area
The ventral tegmental area (VTA) (tegmentum is Latin for ''covering''), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is the ...
, and in some species the dorsal and/or lateral
Hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...
.
Function
The Interpeduncular nucleus is thought to have a broad inhibitory effects on many other brain regions. IPN activity is linked with decreased dopamine release and utilization from dopamine producing regions. The Interpeduncular nucleus is implicated with a role in the regulation of
Rapid eye movement sleep
Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream viv ...
.
Activation of the
GAD2
Glutamate decarboxylase 2 is an enzyme that in humans is encoded by the ''GAD2'' gene.
This gene encodes one of several forms of glutamic acid decarboxylase, identified as a major autoantigen in insulin-dependent diabetes. The enzyme encoded is ...
expressing sub-population of the IPN produced the physical symptoms of nicotine withdrawal suggesting that the misfunction of this region may be an active component of withdrawal.
See also
*
Regions in the human brain
References
External links
Dictionary definition from Mondofacto.com
{{Authority control
Midbrain
Brainstem nuclei