Related Experiment Videos
[Intrathecal midazolam attenuates renal sympathetic nerve activity in rabbits]
K Hashimoto1, F Karasawa, T Satoh
1Department of Anesthesiology, National Defense Medical College, Tokorozawa.
Abstract:
We hypothetized that intrathecal (IT) midazolam (M) affects renal sympathetic nerve activity (RSNA) via benzodiazepine receptors (BZR) at the spinal cord. Under alpha-chloralose anesthesia, 26 rabbits underwent surgical procedures for the cannulation to femoral artery and vein for measuring blood pressure and infusing lactated Ringer solution, respectively. Intrathecal cannulation was performed at the 7th thoracic vertebral level. RSNA was recorded from the nerve raw between the renal artery and vein using a left flank incision. In the neuraxis-intact rabbits, IT administration of low dose M (0.50%) did not affect heart rate (HR), mean arterial pressure (MAP), and integrated RSNA (IRSNA). High concentration of M (0.5%) increased HR, decreased MAP and attenuated IRSNA significantly. In the sino-aortic denervated rabbits, IT administration of 0.5% M decreased MAP and IRSNA, but intravenous 0.2 flumazenil rapidly and significantly increased MAP and IRSNA. This finding suggests that the decrease in IRSNA followed by IT M derives from BZR. In conclusion, IT high concentration of M attenuated RSNA through BZR.
Insights
Intrathecal midazolam (IT M) at high concentrations significantly reduces renal sympathetic nerve activity (RSNA) in rabbits by acting on spinal cord benzodiazepine receptors (BZR). This effect is reversed by flumazenil, confirming the BZR involvement.
Area of Science:
- Neuroscience
- Pharmacology
- Physiology
Context:
- The central nervous system regulates sympathetic nerve activity, influencing cardiovascular function.
- Spinal cord benzodiazepine receptors (BZR) are implicated in modulating autonomic outflow.
- Intrathecal (IT) administration allows direct targeting of spinal cord mechanisms.
Purpose:
- To investigate the effect of intrathecal midazolam (IT M) on renal sympathetic nerve activity (RSNA).
- To determine if the effects of IT M on RSNA are mediated by spinal cord BZR.
- To elucidate the role of spinal BZR in the regulation of sympathetic nerve activity.
Summary:
- High-concentration intrathecal midazolam (0.5%) significantly decreased mean arterial pressure (MAP) and attenuated renal sympathetic nerve activity (RSNA) in rabbits.
- These effects were observed in both neuraxis-intact and sino-aortic denervated rabbits.
- Intravenous flumazenil administration reversed the decrease in MAP and RSNA induced by IT midazolam, indicating mediation via BZR.
Impact:
- This study demonstrates that high-dose intrathecal midazolam attenuates RSNA through spinal BZR.
- Findings suggest a potential role for spinal BZR in modulating sympathetic tone.
- Highlights the importance of considering the site of action for drugs affecting autonomic function.