Angiotensinergic pathway through the median preoptic nucleus in the control of oxytocin secretion and water and sodium intake

The role of central amygdaloid nucleus in regulating the nongenomic effect of aldosterone on sodium intake in the nucleus tractus solitary

OBJECTIVE

The central nucleus of the amygdala (CeA) has dense downward fiber projections towards the nucleus tractus solitary (NTS) and can modulate the activity of NTS taste neurons. However, whether CeA affects the nongenomic role of aldosterone (ALD) in regulating sodium intake at the NTS level remains unclear.

METHODS

First, 40 adult male Sprague Dawley rats were divided into five groups, referring to different concentrations of ALD, to observe the sodium intake pattern compared with the vehicle (n = 8). ALD, the mineralocorticoid receptor antagonist spironolactone (SPI), and ALD + SPI were injected into the NTS. Then, the rats were divided into four groups (n = 16): bilateral/unilateral CeA electrolytic lesions, bilateral/unilateral CeA sham lesions. After recovery, one stainless steel 23-gauge cannula with two tubes was implanted into the rat NTS, and all rats underwent a recovery period of 7 days. Then, each group was divided into two subgroups that received aldosterone or control solution injection, and the cumulative intake of 0.3 mol/L NaCl solution was recorded within 30 min.

RESULTS

Bilateral CeA lesion eliminated the increased 0.3 mol/L NaCl intake induced by aldosterone microinjected into the NTS (CeA lesion: 0.3 ± 0.04 ml/30 min vs. sham lesion: 1.3 ± 0.3 ml/30 min). Unilateral CeA lesion reduced the increased NaCl intake induced by aldosterone microinjected into the NTS compared with the control group (p < .05) in the first 15 min but not in 15-30 min (p > .05). In sham lesion rats, aldosterone (5 ng/0.1 μl) still induced a significant increase in NaCl intake (aldosterone: 1.3 ± 0.3 ml/30 min vs. control: 0.25 ± 0.02 ml/30 min) (p < .05).

CONCLUSION

The results verified that the complete CeA may play an important role in aldosterone to regulate the nongenomic effect on rapid sodium intake.

[Role of the central nucleus of the amygdala in regulating the nongenomic effect of aldosterone on sodium intake in rat nucleus tractus solitarius]

OBJECTIVE

To reveal the nongenomic effect of aldosterone on the regulation of sodium intake in the nucleus tractus solitarius (NTS) and the role of central nucleus of the amygdala (CeA) in regulating this effect.

METHODS

Adult male SD rats were divided into four groups and underwent operations to induce bilateral CeA electrolytic lesions (400 μA, 25 s; n=28), bilateral sham CeA lesions (n=28), unilateral CeA lesions (n=28), or unilateral sham CeA lesions (n=26). After 3 days of recovery, the rats received implantation of a stainless steel 23-gauge cannula wih two tubes into the NTS followed by a recovery period of 7 days. The rats in each group were then divided into two subgroups for microinjection of aldosterone (50 ng/μL) or control solution in the NTS, and the cumulative intake within 30 min of 0.3 mol/L NaCl solution was recorded for each rat.

RESULTS

Bilateral CeA lesions (3 days) eliminated the increased 0.3 mol/L NaCl intake induced by aldosterone microinjected into the NTS (0.3±0.04 mL in CeA lesion group vs 1.3±0.3 mL in sham lesion group). Unilateral CeA lesion (3 days) reduced aldosterone-induced increase of NaCl intake in the first 15 min (P &lt; 0.05) but not in 15-30 min (P &gt; 0.05). In rats with sham lesions, aldosterone (50 ng/μL) still induced a significant increase in NaCl intake[1.3±0.3 mL vs 0.25±0.02 mL in the control group; F (3, 224)=24.0, P &lt; 0.05].

CONCLUSIONS

The regulation of sodium intake by aldosterone is subjected to descending facilitatory modulation by the bilateral CeA, and CeA integrity is essential for aldosterone to execute the nongenomic effect in regulating rapid sodium intake.

Mechanisms of brain renin angiotensin system-induced drinking and blood pressure: importance of the subfornical organ

It is critical for cells to maintain a homeostatic balance of water and electrolytes because disturbances can disrupt cellular function, which can lead to profound effects on the physiology of an organism. Dehydration can be classified as either intra- or extracellular, and different mechanisms have developed to restore homeostasis in response to each. Whereas the renin-angiotensin system (RAS) is important for restoring homeostasis after dehydration, the pathways mediating the responses to intra- and extracellular dehydration may differ. Thirst responses mediated through the angiotensin type 1 receptor (AT1R) and angiotensin type 2 receptors (AT2R) respond to extracellular dehydration and intracellular dehydration, respectively. Intracellular signaling factors, such as protein kinase C (PKC), reactive oxygen species (ROS), and the mitogen-activated protein (MAP) kinase pathway, mediate the effects of central angiotensin II (ANG II). Experimental evidence also demonstrates the importance of the subfornical organ (SFO) in mediating some of the fluid intake effects of central ANG II. The purpose of this review is to highlight the importance of the SFO in mediating fluid intake responses to dehydration and ANG II.