Considering this, it is relevant to study which hypothalamic

magnocellular nucleus mediates the cardiovascular Inhibitor Library in vitro response evoked by carbachol microinjection into the BST. Taking that into consideration, we evaluated the hypothesis that PVN and/or SON neurons are part of the neural pathway related to cardiovascular responses following carbachol microinjection into the BST of unanesthetized rats. For this, we investigated cardiovascular responses evoked by carbachol microinjection into the BST before and after PVN or SON pretreatment, either ipsilateral or contralateral in relation to BST microinjection site, with the nonselective neurotransmission blocker cobalt chloride (CoCl2). Microinjection of aCSF into the BST (n = 5) did not affect either MAP (99 ± 2 vs. 98 ± 3 mm Hg, t = 0.2, P > 0.05) or HR (379 ± 11 vs. 352 ± 9 bpm, t = 1.3, P > 0.05) baseline values. However, microinjection of carbachol into the BST caused significant pressor and bradycardiac responses in unanesthetized rats ( Fig. 1). Photomicrography of a coronal brain section showing a representative microinjection site into the BST is presented in Fig. 2. Diagrammatic representation of the BST indicating microinjection sites into the BST of all animals used in the present

study is also shown in Fig. 2. Microinjection of carbachol (n = 6) buy CT99021 into the BST significantly increased plasma vasopressin content (aCSF: 2.3 ± 0.5 pg/mL vs. carbachol: 21.3 ± 3.6 pg/mL, t = 5, P < 0.005), when compared to the control group that received vehicle (aCSF) injection into the BST (n = 6). Microinjection of aCSF into the ipsilateral SON (n = 7) did not affect either MAP (98 ± 2 vs. 101 ± 3 mm Hg, t = 0.5, P > 0.05) or HR

(352 ± 7 vs. 367 ± 11 bpm, t = 1.5, P > 0.05) baseline values. Pretreatment of the ipsilateral SON with aCSF also did not affect the pressor (43 ± 2 vs. 38 ± 2 mm Hg, t = 2.3, P > 0.05) and bradycardiac (− 67 ± 7 vs. − 64 ± 8 bpm, t = 0.2, P > 0.05) response to carbachol microinjection into the BST ( Fig. 1A). Microinjection of CoCl2 into the ipsilateral SON (n = 7) did not affect either MAP (102 ± 2 vs. 100 ± 2 mm Hg, t = 0.6, P > 0.05) or HR (351 ± 6 vs. 356 ± 8 bpm, t = 0.7, P > 0.05) baseline values. However, ipsilateral SON pretreatment with CoCl2 significantly reduced the pressor (44 ± 2 vs. 6 ± 1 mm Hg, t = 16, P < 0.0001) and bradycardiac (− 74 ± 6 vs. − 12 ± 1 bpm, FAD t = 10, P < 0.0001) response to carbachol microinjection into the BST ( Fig. 1A). Time-course analysis indicated a significant effect of SON pretreatment with CoCl2 in carbachol cardiovascular effects (ΔMAP: F(1,456) = 468, P < 0.0001 and ΔHR: F(1,456) = 111, P < 0.0001), a significant effect over time (ΔMAP: F(37,456) = 23, P < 0.0001 and ΔHR: F(37,456) = 11, P < 0.0001), and an interaction between treatment and time (ΔMAP: F(37,456) = 20, P < 0.0001 and ΔHR: F(37,456) = 4, P < 0.0001) ( Fig. 1B). Microinjection of aCSF into the contralateral SON (n = 6) did not affect either MAP (100 ± 3 vs.