Catecholaminergic neurons in the comissural region of the nucleus of the solitary tract modulate hyperosmolality-induced responses

Abstract

Noradrenergic A2 neurons of the nucleus of the solitary tract (NTS) have been suggested to contribute to body fluid homeostasis and cardiovascular regulation. In the present study, we investigated the effects of lesions of A2 neurons of the commissural NTS (cNTS) on the c-Fos expression in neurons of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, arterial pressure, water intake, and urinary excretion in rats with plasma hyperosmolality produced by intragastric 2 M NaCl (2 ml/rat). Male Holtzman rats (280-320 g) received an injection of anti-dopamine-β-hydroxylase-saporin (12.6 ng/60 nl; cNTS/A2-lesion, n = 28) or immunoglobulin G (IgG)-saporin (12.6 ng/60 nl; sham, n = 24) into the cNTS. The cNTS/A2 lesions increased the number of neurons expressing c-Fos in the magnocellular PVN in rats treated with hypertonic NaCl (90 ± 13, vs. sham: 47 ± 20; n = 4), without changing the number of neurons expressing c-Fos in the parvocellular PVN or in the SON. Contrary to sham rats, intragastric 2 M NaCl also increased arterial pressure in cNTS/A2-lesioned rats (16 ± 3, vs. sham: 2 ± 2 mmHg 60 min after the intragastric load; n = 9), an effect blocked by the pretreatment with the vasopressin antagonist Manning compound (0 ± 3 mmHg; n = 10). In addition, cNTS/A2 lesions enhanced hyperosmolality-induced water intake (10.5 ± 1.4, vs. sham: 7.7 ± 0.8 ml/60 min; n = 8-10), without changing renal responses to hyperosmolality. The results suggest that inhibitory mechanisms dependent on cNTS/A2 neurons reduce water intake and vasopressin-dependent pressor response to an acute increase in plasma osmolality.

Medullary Noradrenergic Neurons Mediate Hemodynamic Responses to Osmotic and Volume Challenges

“…In these experiments, we showed that animals with A1 and A2 lesions did not recover blood flow. Studies with a similar injury time show that the loss of ∼60% of A1 and/or A2 neurons is effective in establishing different responses in the control animals (Pedrino et al, 2012;da Silva et al, 2013;Freiria-Oliveira et al, 2015;Naves et al, 2018). Current results consistently demonstrated that lesions in two areas effectively attenuated the HSI-induced recovery.…”

Organization of the Catecholaminergic System in the Short-Lived Fish Nothobranchius furzeri

“…Comparable NAergic neurons have been described in the caudal hindbrain of other teleosts, holosteans, cladistians and lungfish ( Ma, 1997 ; Kaslin and Panula, 2001 ; Lopez and Gonzalez, 2017 ; Lopez et al, 2019 ; Lozano et al, 2019 ). In mammals, the NAergic neurons of the medulla oblongata correspond to the A1-A2 group and are involved in sympathetic functions such as the control of arterial pressure, respiratory pacemaking and response to pH ( Freiria-Oliveira et al, 2015 ). It has been proposed that the NAergic neurons in the caudal rombencephalon have a conserved function in vertebrates ( Smeets and Gonzalez, 2000 ).…”

Organization of the catecholaminergic systems in two basal actinopterygian fishes, Polypterus senegalus and Erpetoichthys calabaricus (Actinopterygii: Cladistia)

“…Other putative noradrenergic cells (TH+/DA−) in cladistians are situated in the caudal part of the Nsol and the area postrema, as it has also been reported in teleosts, lungfishes, and amphibians (González et al, ; González & Smeets, ; López & González, ; Ma, ). The CA cells of Nsol and area postrema might be comparable to the mammalian groups A1/A2 involved in local control of the respiratory pacemaker, arterial pressure and related functions, such as swallowing and response to pH or changes induced by hyperosmolality (Freiria‐Oliveira et al, ). The presence of dopaminergic/noradrenergic cells in the caudal rhombencephalon is a highly conserved feature in vertebrates (Table ) and probably these cells are involved in similar functions.…”