The nucleus raphe pallidus receives afferent connections from 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 ...

, the

Paraventricular nucleus of hypothalamus The paraventricular nucleus (PVN, PVA, or PVH) is a nucleus in the hypothalamus. Anatomically, it is adjacent to the third ventricle and many of its neurons project to the posterior pituitary. These projecting neurons secrete oxytocin and a smaller ...

, central nucleus of the

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verteb ...

, lateral hypothalamic area, and

parvocellular reticular nucleus The parvocellular reticular nucleus is part of the brain located dorsolateral to the caudal pontine reticular nucleus. The dorsal portion of the reticular nucleus has been shown to innervate the mesencephalic trigeminal nucleus and its surrounding ...

. Also, the nucleus raphe pallidus receives afferents from the medial

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 ...

, median preoptic nucleus and lateral paragigantocellular reticular nuclei. The nucleus raphe pallidus has recently been shown to be involved in the activation of a fever as an immunoreaction. It has been implied that the preoptic area is constantly inhibiting the raphe pallidus, especially the rostral portion, with GABA. When the preoptic area receives immune signals from the body, the inhibition stops and the rostral portion of the nucleus raphe pallidus excites the intermediolateral cell column, which induces a fever. The nucleus raphe pallidus has also been known to mediate the

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (su ...

response, an extremely high heart rate known to be incited by emotional or psychological stress. Microinjections of a GABA-a antagonist into the nucleus raphe pallidus, induces an increased heart rate. Conversely, microinjections of muscimol, a GABA-a

agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ago ...

, inhibit tachycardia in rats under air-stress stimuli.Zaretsky, Dmitry V. et al. Microinjection of muscimol into raphe pallidus suppresses tachycardia associated with air stress in conscious rats. Journal of Physiology (2003), 546.1, pp. 243-250 In both of these cases, GABA is mediating two different sympathetic responses, so clearly the nucleus raphe pallidus is a far more a complex nucleus than previously thought.

References

{{Authority control Medulla oblongata

See also

References