Tuberoinfundibular pathway: what is it and how does this brain pathway work?

This dopaminergic pathway in the brain runs from the hypothalamus to the pituitary gland.

Brain pathways are routes that connect different regions of the brain. In this article we will learn about one of the dopaminergic pathways, the tuberoinfundibular pathway.. This pathway is related to a very important hormone: prolactin.

We will see the importance of this pathway, and we will also learn about the other three most important dopaminergic pathways, which are closely related to schizophrenia or other psychotic disorders.

Dopaminergic pathways

The tuberoinfundibular pathway is one of the 4 dopaminergic pathways we have in the brain. The other three are: the mesolimbic, mesocortical and nigrostriatal pathways.

Each dopaminergic pathway is in fact a brain pathway of neurons that transmits dopamine from one area of the brain to another.. Dopamine has been, and is, one of the neurotransmitters most related to schizophrenia, as we will see below.

Tuberoinfundibular pathway: characteristics

At the neuroanatomical level, the tuberoinfundibular pathway projects from the hypothalamus to the anterior pituitary gland. More specifically, it runs from a very specific nucleus of the mediobasal hypothalamus, called the arcuate nucleus (also called the tuberal region), to the medial eminence or infundibular region. On the other hand, the term "infundibular" refers to the infundibulum, the infundibular region. refers to the infundibulum, a structure from which the pituitary gland develops..

The tuberoinfundibular pathway influences the secretion of some hormones by the pituitary gland, such as prolactin (this is a hormone that, among other functions, secretes milk during maternity), which is secreted more specifically in the adenohypophysis.

Thus, the dopaminergic neurons of this pathway are usually active and inhibit are usually active and inhibit prolactin release.i.e., the presence of dopamine in the tuberoinfundibular pathway inhibits prolactin synthesis, and also favors somatotropin synthesis.

Blockage of the pathway: hyperprolactinemia.

The classic antipsychotics that act by reducing dopamine in patients with psychosis or schizophreniaend up generating the side effect of an abnormal increase in prolactin levels. This occurs because they block D2 (dopamine) receptors, reducing their level and by extension, inhibiting the functioning of the tuberoinfundibular pathway.

The increase in prolactin levels in the Blood through the tuberoinfundibular pathway, called hyperprolactinemia, involves a series of symptoms:

On the one hand, there is an increase in milk secretion in postpartum stages (during breastfeeding). (during breastfeeding), as well as the presence of galactorrhea (spontaneous breast secretions outside the lactation period), gynecomastia (enlargement of the mammary glands) and mastodynia (breast pain).

In addition, hyperprolactinemia can also cause irregularities in the menstrual cycle in women, visual problems, headache, amenorrhea and other possible problems.In addition, hyperprolactinemia may also lead to irregularities in the menstrual cycle in women, visual problems, headache, amenorrhea and other possible problems such as sexual dysfunction (e.g. it significantly affects fertility and reduces sexual desire).

Hyperprolactinemia occurs in both males and females.

The other dopaminergic pathways

In addition to the tuberoinfundibular pathway, three other dopaminergic pathways are involved in different hormonal processes. are involved in different hormonal and bodily processes.In addition, and as mentioned above, some of them have been significantly linked to schizophrenia.

Destination and origin

The mesocortical pathway goes from the ventral tegmental area (VTA) of the brainstem to various areas of the cortex, especially to the limbic cortex and the dorsolateral prefrontal cortex. The mesolimbic pathway runs from the dopaminergic cell bodies of the ventral tegmental area (VTA) to limbic areas of the brain, such as the nucleus accumbens. Finally, the nigrostriatal pathway goes from the substantia nigra to the basal ganglia or striatum (extrapyramidal system).

Relationship to schizophrenia and Parkinson's disease

Hyperfunctioning of the mesolimbic dopaminergic pathway has been associated with the positive symptomatology of schizophrenia (recall that positive symptoms include hallucinations, delusions, disorganized behavior, etc.).

In contrast, hypofunctioning of the mesocortical dopaminergic pathway has been related to the negative symptoms of schizophrenia (abulia, anhedonia, tendency to isolation, affective flattening, etc.).

For its part, the nigrostriatal pathway has been related to other pathologies such as Parkinson's disease (its blockade implies a reduction in dopamine levels, and this is related to Parkinson's disease, producing symptoms such as akathisia and dystonia). In contrast, an increase of dopamine in the nigrostriatal pathway is related to hyperkinetic disorders such as chorea or tics. If the DA2 receptor in this pathway is chronically blocked, tardive dyskinesia appears.

Bibliographical references:

• Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Educación.
• Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.
• Rosenweig, M., Breedlove, S., Watson, N. (2005). Psychobiology: an introduction to behavioral, cognitive and clinical neuroscience. Barcelona: Ariel.