Hypertension affects over 50% of adults and is associated with the overactivation of the paraventricular nucleus of the hypothalamus (PVH), which regulates neurohumoral and sympathetic output. We investigate perineuronal nets (PNNs) as a potential mechanism underlying this overactivation. PNNs are lattice-like extracellular structures surrounding the soma and proximal dendrites of neurons, influencing their firing and circuit plasticity. In addition to PVH, we examine PNN changes in the perifornical area of the anterior hypothalamus (PeFAH), an inhibitory, PNN-rich region adjacent to and potentially projecting to the PVH. We hypothesize that hypertension increases PNNs in the PVH, enhancing excitability, while decreasing PNNs in the PeFAH, reducing its inhibitory output – together contributing to PVH overactivation. To test this, 3–5-month-old male and female C57BL6 mice were implanted with s.c. deoxycorticosterone acetate (DOCA) pellets and given 0.9% NaCl in drinking water. After 21 days of DOCA-salt treatment, perineuronal nets (PNNs) were quantified using the marker Wisteria Floribunda Agglutinin (WFA). In the PVH, DOCA-salt males showed a significant increase in WFA+ area (%) (mean ± SD) (3.636 ± 1.636, n = 9) compared to sham controls (2.497 ± 0.9924, n = 10; p = 0.0255, two-tailed unpaired t-test). This corresponded to a higher PNN number (n/mm 2 ) in treated mice (DOCA: 44.77 ± 11.64; Sham: 35.63 ± 6.198; p = 0.0447). In contrast, females showed no significant change in WFA+ area (DOCA: 4.226 ± 1.386; Sham: 3.966 ± 1.747; p = 0.5532) or PNN number (DOCA: 64.87 ± 16.88; Sham: 71.48 ± 11.70; p = 0.4011), despite elevated blood pressure. In the PeFAH, DOCA-salt males exhibited a reduction in normalized WFA+ area (DOCA: 0.9200 ± 0.0656; Sham: 1.001 ± 0.0927; p = 0.0440), which was not observed in females (DOCA: 0.9518 ± 0.0858; Sham: 1.000 ± 0.0851; p = 0.2953). These results suggest that increased PVH PNNs may activate previously ‘silent’ neurons, while reduced PNNs in the PeFAH may weaken inhibitory output – together contributing to PVH overactivation in male mice during hypertension.
Blanco et al. (Mon,) studied this question.