Splenic reflex modulation of central cardiovascular regulatory pathways

Area of Science:

• Neuroscience
• Physiology
• Renal Science

Background:

• The splenorenal reflex impacts mean arterial pressure (MAP) and renal function.
• Spinal pathways are known mediators, but central pathway involvement is less understood.

Purpose of the Study:

• To investigate if central neural pathways mediate the effects of elevated splenic venous pressure.
• To identify specific brain regions activated by splenic venous pressure changes.

Main Methods:

• Used conscious rats with controlled splenic vein occlusion (SVO) to elevate splenic venous pressure.
• Quantified Fos-labeled neurons in key brain areas (NTS, PVN, SON, SFO) in intact and denervated rats.
• Monitored MAP, splenic venous pressure, and renal afferent nerve activity.

Main Results:

• SVO induced Fos expression in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of intact rats.
• Renal denervation altered PVN activation, while combined renal and splenic denervation abolished PVN and SON activation.
• In renal-denervated rats, SVO affected Fos expression in the nucleus of the tractus solitarius (NTS) and subfornical organ (SFO), abolished by further denervation.
• SVO decreased right atrial pressure, increased renal afferent activity, and increased MAP in intact rats.

Conclusions:

• Elevated splenic venous pressure activates hypothalamic centers (PVN, SON) via both splenic and renal afferent nerves.
• Renal afferent input is crucial for NTS activation during SVO.
• Reduced cardiac preload may influence NTS activation in the absence of renal input.