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Angiotensin II Signaling in the Median Preoptic Nucleus Persists in Renin KO Rats: an in vitro Sniffer Cell Study
Author(s) -
Farmer George,
Bachelor Martha,
Cunningham J.
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.02864
Subject(s) - subfornical organ , renin–angiotensin system , endocrinology , angiotensin ii , medicine , losartan , median preoptic nucleus , supraoptic nucleus , stimulation , hypothalamus , chemistry , receptor , biology , blood pressure
The brain is sensitive to Angiotensin II (ANG II) and we have previously shown that ANG II is released by brain slices containing the median preoptic nucleus (MnPO) and subfornical organ (SFO) in an activity dependent manner. Here, we test the role of renin in ANG II synthesis and signaling in the SFO to MnPO pathway in a renin KO rat model. Sniffer cells were used to detect the presence of ANG II in male and female (2‐6 mo) SS.SS Ren1‐m1 renin knock out rats (obtained from Medical College of Wisconsin). Sniffer cells consisted of Chinese Hamster Ovary cells transfected with a commercially available plasmid for the angiotensin type 1a (AT1a) receptor (Origene Tech.) and R‐GECO (Addgene #32462) as previously described. Sniffer cells were placed on the median preoptic nucleus (MnPO) in sagittal in vitro brain slices (produced using standard slice procedures). Both spontaneous and electrically evoked (SFO stimulation) changes in fluorescent intensity of sniffer cells on the MnPO were measured. Recording were repeated with a 10 min bath application of the renin inhibitor aliskerin (10 um). In some slices, additional recordings were made in the presence of the AT1a receptor inhibitor losartan (10 um). Sniffer cell recordings were made from 7 SS.SS Ren1‐m1 homozygous KO rats (HomoKO, 2 male, 5 female), 7 heterozygous KOs (HetKO, 4 male, 3 female), and 2 WT (1 male, 1 female). The frequency of spontaneous sniffer cell activity in slices from WT (n = 17), HetKO (n = 100), and HomoKO (n = 50) slices were not different and were comparable to rates previously observed in Sprague‐Dawley rats. Bath application of losartan 10 (uM) was effective in blocking all spontaneous sniffer cell activity. Bath application of aliskerin (10 uM) significantly reduced the frequency of sniffer cell responses in WT (p < 0.001) and HetKO (p < 0.001) slices. However, the reduction in spontaneous sniffer cell responses in HomoKO slices was far less robust (p < 0.05). In WT rats, there was no difference between males and females in the frequency of spontaneous sniffer cell responses during baseline recordings (male n = 6, female n = 11 sniffer cells). Aliskerin induced a trend toward reduce activity in males and induced a robust reduction in activity from females (p < 0.001). Baseline activity in male HetKO (n = 56) was reduced compared to Het KO female (n = 44) activity (p < 0.05). Aliskerin reduced sniffer cell activity in both male (p < 0.001) and female (p < 0.001) slices but there was no difference in the aliskerin effects between Het KO males and females. In slices from HomoKOs, baseline activity was present in both male (n = 23) and female (n = 27). Aliskerin did not influence sniffer cell activity in males or females. There was no difference between male and female in baseline activity or the effects of aliskerin. Furthermore, there were no estrous cycle differences in the baseline activity and the effects of aliskerin in female HetKO and HomoKO slices. The current study indicates that renin contributes to ANG II signaling in the MnPO under normal conditions but that alternate ANG II biosynthetic pathways may become active in the absence of renin.