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Mu and kappa opioid modulation of olfactory bulb evoked potentials
H Pérez1, A Hernández, H Inostroza
1Laboratory of Neurophysiology and Biophysics, University of Chile, Santiago.
Abstract:
Modulatory influences of the mu opioid agonist morphine and the kappa opioid agonist U-50, 488H on field-evoked potentials from the main olfactory bulb (MOB) in response to stimulation of the olfactory nerve were studied. Topically administered morphine upon the MOB dorsal surface produced a noloxone-sensitive depression of the late component of the response without modifying the early one, while topical administration of U-50, 488H suppressed both the early and the late components. Naloxone did not antagonize U-50, 488 effects. Results indicate that mu and kappa opioid agonists can interfere with sensory transmission at the level of second-order neurons of the olfactory pathway, the mitral and/or tufted cells.
Insights
Morphine and U-50,488H, opioid agonists, affect olfactory bulb signaling. Morphine selectively impacts later responses, while U-50,488H affects both early and late olfactory nerve signal components.
Area of Science:
- Neuroscience
- Pharmacology
- Sensory Systems
Background:
- The main olfactory bulb (MOB) processes olfactory information.
- Opioid receptors are known to modulate neuronal activity in various brain regions.
Purpose of the Study:
- To investigate the differential effects of mu and kappa opioid agonists on olfactory nerve-evoked potentials in the MOB.
- To determine the involvement of opioid receptor subtypes in olfactory sensory transmission.
Main Methods:
- Field-evoked potentials in the MOB were recorded following olfactory nerve stimulation.
- The effects of topically applied mu-opioid agonist morphine and kappa-opioid agonist U-50,488H were assessed.
- The role of naloxone as an opioid antagonist was evaluated.
Main Results:
- Morphine application resulted in a naloxone-sensitive depression of the late component of the MOB response.
- U-50,488H application suppressed both early and late components of the MOB response.
- Naloxone failed to antagonize the effects of U-50,488H.
Conclusions:
- Mu and kappa opioid agonists differentially modulate olfactory sensory transmission at the MOB level.
- These findings suggest that opioid receptors are present on second-order olfactory neurons (mitral and/or tufted cells).
- Opioid systems can influence the processing of olfactory information within the main olfactory bulb.