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Opioid signalling in the rat rostral ventrolateral medulla
Patrice G Guyenet1, Ruth L Stornetta, Ann M Schreihofer
1Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia, USA. pgg@virginia.edu
Clinical and Experimental Pharmacology & Physiology
|March 22, 2002
Summary
Opioid signaling in the rostral ventrolateral medulla (RVLM) influences blood pressure control. Opioid peptides modulate presympathetic neurons via pre- and post-synaptic mechanisms involving mu-opioid receptors.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Pharmacology
Background:
- The rostral ventrolateral medulla (RVLM) is crucial for regulating blood pressure.
- Opioid peptides play a role in neural control systems.
- Understanding opioid actions in the RVLM is key to cardiovascular regulation.
Purpose of the Study:
- To review opioid signaling in the RVLM.
- To explore the implications for neural control of blood pressure.
- To elucidate the role of opioid peptides and receptors in RVLM function.
Main Methods:
- Review of existing literature on opioid signaling in the RVLM.
- Analysis of preproenkephalin (PPE) mRNA expression in RVLM neurons.
- Examination of mu-opioid receptor (MOR) expression and function in RVLM circuits.
- Investigation of pre- and post-synaptic effects of MOR agonists in brain slices.
Main Results:
- PPE mRNA is found in barosensitive, bulbospinal presympathetic neurons (C1 and non-C1) and local GABAergic neurons in the RVLM.
- RVLM presympathetic neurons receive enkephalinergic inputs and express MOR.
- MOR agonists induce inhibitory post-synaptic effects (increased gK) and presynaptic effects (disfacilitation, possibly dishinhibition) on RVLM presympathetic neurons.
- Both pre- and post-synaptic modulation by MOR agonists has been demonstrated.
Conclusions:
- Opioid signaling extensively modulates the medullospinal network controlling sympathetic tone and arterial pressure.
- Opioid peptides are produced by RVLM presympathetic and local inhibitory neurons.
- RVLM presympathetic neurons are regulated by opioid peptides at both pre- and post-synaptic levels, involving mu- and possibly delta-opioid receptors.