Ipsilateral somatic nerves mediate histamine-induced vasosensory reflex responses involving perivascular afferents in rat models

Figures

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  Figure 1. Flowcharts illustrating the experimental protocol. In the first part of the study, normal saline was instilled into the femoral artery and the cardiorespiratory (CVR) responses were recorded. In the second part of the study, histamine in three different concentrations was instilled in different groups of rats and the CVR responses were recorded. In the third part of the study, 10 mM of histamine (optimal dose from concentration–response experiments) was instilled intra-arterially (i.a) after ipsilateral sciatic and femoral neurotomy (NX), bilateral vagotomy (VagX) and pre-treatment with lignocaine (+Ligno) in different groups of rats and the CVR responses were recorded.

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  Figure 2. Representative prototypes of original recordings showing the effects of different concentrations of histamine (Hist) on respiration (Resp), blood pressure (BP) and electrocardiogram (ECG) as compared to normal saline control. The responses are shown at different time intervals as indicated in the lower panel. The points of instillation are shown by dotted lines. The horizontal line in each panel is 15 s for all parameters.

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  Figure 3. Time-response relationship of different histamine concentrations on mean arterial pressure (MAP), heart rate (HR), respiratory frequency (RF) and respiratory minute volume (RMV). The time matched control responses after saline are given in the left panel of each row along with 1 mM concentration of histamine. The values are in mean ± SEM from 6 experiments for each concentration. An asterisk (*) indicates significant difference of responses as compared with control group [P < 0.05, two sided Dunnett’s test] and with the initial value [P < 0.05, Paired t-test] for all concentrations of histamine. Arrows indicate the point of injection of saline/histamine.

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  Figure 4. Representative prototypes of original recordings showing the effects of 10 mM histamine (Hist) on respiration (Resp), blood pressure (BP) and electrocardiogram (ECG), after ipsilateral sciatic and femoral neurotomy (+NX), bilateral vagotomy (+VagX) and pre-treatment with lignocaine (+Ligno). The responses are shown at different time intervals as indicated in the lower panel. The points of instillation of Hist after interventions are shown by dotted lines. The horizontal line in each panel is 15 s for all parameters.

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  Figure 5. Time-response relationship of 10 mM histamine on mean arterial pressure (MAP), respiratory frequency (RF) and respiratory minute volume (RMV), after ipsilateral sciatic and femoral nerve sectioning (+NX), bilateral vagotomy (+VagX) and pre-treatment with lignocaine (+Ligno). The responses of histamine (10 mM) only group are given in the left panel of each row along with neurotomized group. The values are in mean ± SEM from 6 experiments in each group. (*) indicates P < 0.05, two sided Dunnett’s test as compared with the histamine (10 mM) only group; (#) indicates P < 0.05, Unpaired t-test as compared with the histamine (10 mM) only group. Arrows indicate the point of injection of histamine. HR responses are not included in this figure as 10 mM histamine did not produced significant HR alterations as compared to the control group [Fig. 3].