Integration in the PVN: another piece of the puzzle

Abstract

THE PARAVENTRICULAR NUCLEUS (PVN) of the hypothalamus is a major integratory region in the hypothalamus that helps maintain homeostasis. Functionally, the PVN is involved in regulation of food intake, responses to stress, modulating metabolic rate, thermoregulation, and regulation of cardiovascular function and the autonomic nervous system (2,4,7,14,30,34,40). It is unique in that in contains primarily estrogen receptor ␤-receptors that regulate transcripts for vasopressin and oxytocin and also affect the function of preautonomic neurons (24,35). The PVN influences neuroendocrine function and the production and secretion of substances such as vasopressin, thyrotropin-releasing hormone (TRH), orexin, corticotropinreleasing factor (CRF), and oxytocin (6,12,21). The PVN communicates with other hypothalamic nuclei such as the dorsal medial nucleus, the arcuate nucleus, and the caudal hypothalamus (1,8,13,26). It receives inputs, either directly or indirectly, from rostral brain regions, including the limbic system and amygdala, and caudal brain stem regions such as the nucleus tractus solitarius (A2 region), A5 region of the pons, the rostral ventrolateral medulla (RVLM), and locus ceruleus (17,20,30,(35)(36)(37)(38). Outputs to autonomic regions that modulate sympathetic nervous system and cardiovascular function have been extensively described (10,27,35,39,40,42). In contrast, less research has focused on the role of the PVN in control of breathing.Early research into the role of the hypothalamus on ventilation by Redgate (29) indicated that depression of hypothalamic function by injection of thiopental or hypothalamic lesions also depressed ventilation in anesthetized adult cats. In 1974, Kastella and colleagues (16) showed that respiratory-related neurons in the anterior hypothalamus of cats existed adjacent to areas that receive baroreceptor and chemoreceptor input. These investigators suggested that respiratory and cardiovascular integration occurred in this portion of the hypothalamus in a similar manner to that described in the brain stem. In 1997, Yeh and coworkers (41) demonstrated that the PVN influences respiratory timing and activity in urethane-anesthetized Wistar rats that were vagotomized and ventilated. Diaphragmatic electromyographic (D EMG ) activity was used to determine ventilatory output. Bilateral microinjection of glutamate into the PVN stimulated frequency of breathing and D EMG peak activity. Concomitantly, arterial blood pressure also increased. By microinjection of 4% Fluorogold into the phrenic nucleus, Yeh and coworkers (41) showed that there were direct connections between the PVN and phrenic motoneurons and the diaphragm and indirect connections between the PVN and brain stem bulbospinal neurons. Subsequently, Schlenker and colleagues (32) reported that unilateral microinjection of bicuculline, a ␥-aminobutyric acid (GABA) A receptor antagonist, into the PVN of conscious rats increased mean arterial pressure (MAP), breathing frequency, the volume of a breath, heart rate, and oxygen co...

Stimulation of the hypothalamic paraventricular nucleus modulates cardiorespiratory responses via oxytocinergic innervation of neurons in pre-Bötzinger complex

“…The PVN is involved in coordination of respiratory and cardiovascular responses to a number of stimuli (39,53), including those from peripheral chemoreceptors (41,48). Previously, it has been shown that bilateral microinjection of glutamate into the PVN in urethane-anesthetized vagotomized and ventilated rats caused an increased in peak D EMG activity and D EMG frequency discharge.…”

“…It receives inputs from visceral receptors, circulating hormones and limbic circuits and transmits information to multiple CNS sites (11,53), including cell groups regulating respiratory drive (27,30,58) and sympathetic outflow (6,13,24,26,27,41,48).…”

GABA in the paraventricular nucleus tonically suppresses baroreflex function: alterations during pregnancy

“…THE PARAVENTRICULAR NUCLEUS (PVN) of the hypothalamus integrates multiple forebrain and brain stem inputs to regulate the autonomic nervous system via outputs that ultimately converge with focal brain stem nuclei, such as the rostral ventrolateral medulla, as well as preganglionic sympathetic neurons in the spinal cord (7,27,29,32). While the contribution of the PVN and its connections to basal sympathetic tone at rest in normal animals is minimal, it appears to drive increased sympathetic activity in such pathophysiological states as hypertension, heart failure, and water deprivation (7,27).…”

“…While the contribution of the PVN and its connections to basal sympathetic tone at rest in normal animals is minimal, it appears to drive increased sympathetic activity in such pathophysiological states as hypertension, heart failure, and water deprivation (7,27). Moreover, the PVN mediates, in part, autonomic responses to diverse homeostatic challenges, such as changes in food intake, blood volume, stress, and body temperature (29). However, whether and how the PVN can also influence the regulation of the baroreceptor reflex is currently unclear.…”

Projeções hipotalâmicas do núcleo supraquiasmático com base na distribuição de fibras imunorreativas para VIP e AVP no Cebus apella.

“…Esta localização no meio do diencéfalo margeando uma região de grande difusão de líquido céfalo-raquidiano torna o PaV a maior região integradora do hipotálamo, envolvida na manutenção da homeostase (Schlenker, 2005 (Reghunandanan, Reghunandanan, 2006). Funcionalmente, o…”