Inhibitory mechanism of the nucleus of the solitary tract involved in the control of cardiovascular, dipsogenic, hormonal, and renal responses to hyperosmolality

Abstract

The nucleus of the solitary tract (NTS) is the primary site of visceral afferents to the central nervous system. In the present study, we investigated the effects of lesions in the commissural portion of the NTS (commNTS) on the activity of vasopressinergic neurons in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, plasma vasopressin, arterial pressure, water intake, and sodium excretion in rats with plasma hyperosmolality produced by intragastric 2 M NaCl (2 ml/rat). Male Holtzman rats with 15-20 days of sham or electrolytic lesion (1 mA; 10 s) of the commNTS were used. CommNTS lesions enhanced a 2 M NaCl intragastrically induced increase in the number of vasopressinergic neurons expressing c-Fos in the PVN (28 ± 1, vs. sham: 22 ± 2 c-Fos/AVP cells) and SON (26 ± 4, vs. sham: 11 ± 1 c-Fos/AVP cells), plasma vasopressin levels (21 ± 8, vs. sham: 6.6 ± 1.3 pg/ml), pressor responses (25 ± 7 mmHg, vs. sham: 7 ± 2 mmHg), water intake (17.5 ± 0.8, vs. sham: 11.2 ± 1.8 ml/2 h), and natriuresis (4.9 ± 0.8, vs. sham: 1.4 ± 0.3 meq/1 h). The pretreatment with vasopressin antagonist abolished the pressor response to intragastric 2 M NaCl in commNTS-lesioned rats (8 ± 2.4 mmHg at 10 min), suggesting that this response is dependent on vasopressin secretion. The results suggest that inhibitory mechanisms dependent on commNTS act to limit or counterbalance behavioral, hormonal, cardiovascular, and renal responses to an acute increase in plasma osmolality.

Differential modulation of sympathetic and respiratory activities by cholinergic mechanisms in the nucleus of the solitary tract in rats

“…; Blanch et al . ). However, the combined antagonism of both glutamatergic and purinergic receptors in the cNTS did not affect the chemoreflex‐induced tachypnoea (Braga et al .…”

“…; Blanch et al . ). Neurones of the NTS are also part of the dorsal respiratory group involved in processing information arising from pulmonary stretch receptors and peripheral chemoreceptors (Bianchi et al .…”

“…Baroreceptor afferents make the first synapse mainly at the level of the iNTS (Ciriello et al 1994), whereas the cNTS receives mostly peripheral chemoreflex afferents (Ciriello et al 1994). Lesions of the iNTS abolish the baroreflex, whereas cNTS lesions impair the chemoreflex, leaving the baroreflex unchanged (Miura & Reis, 1972;Colombari et al 1996;Schreihofer et al 1999;Blanch et al 2013). Neurones of the NTS are also part of the dorsal respiratory group involved in processing information arising from pulmonary stretch receptors and peripheral chemoreceptors (Bianchi et al 1995;Costa-Silva et al 2010).…”

CNS sites activated by renal pelvic epithelial sodium channels (ENaCs) in response to hypertonic saline in awake rats

“…A potential pathway from the ARN to SON has been suggested in earlier work (Ciriello et al, 2004; Fitch et al, 2000; Huang and Weiss, 1999). Others have proposed input to the SON from sodium loading in the vasculature or CNS (Blanch et al, 2013; Carlson et al, 1997; Moellenhoff et al, 1998; Morita et al, 1997; Rinaman et al, 1997). We suggest that sodium sensitive ENaCs in the renal pelvis increase ARN activity that ultimately reaches neurons in the SON and PVH which regulate vasopressin release (Day and Ciriello, 1985).…”

“…Many authors have reported activation of several sites including circumventricular organs after intravenous (Bisley et al, 1996; Ho et al, 2007), intragastric (Kobashi et al, 1993; Carlson and Osborn, 1998; Carlson et al, 1997; Blanch et al, 2013) intracerebroventricular (Moellenhoff et al, 1998), or intraportal vein administration (Morita et al, 1997). These typically include the NTS, AP, PBel, SON and PVH and have been ascribed to either direct increases in plasma or CSF osmolality or to activation of sodium receptors in the portal vein.…”