Opioids decrease high-voltage activated calcium currents in acutely dissociated neostriatal neurons.
Although the distribution of opioid receptors is central to the patch-matrix model of neostriatal organization, it has been unclear whether these receptors are located post-synaptically. Moreover, it has not yet been clarified whether opioid receptor activation in neostriatum results in the modulation of calcium and/or potassium conductances. To test this, neostriatal neurons were acutely isolated and their sensitivity to opioid receptor agonists determined. At nanomolar concentrations, both the mu-agonist [D-Ala2, MePhe4,Gly-ol5]-enkephalin (DAMGO) and the delta-agonist [D-Pen2, D-Pen5]-enkephalin (DPEPE) reversibly decreased whole-cell calcium currents in medium-sized neurons. These effects were blocked by the opiate antagonist naloxone. These findings argue that activation of post-synaptic, opioid receptors is capable of modulating the excitability of neostriatal neurons.
Clinica Neurologica, Università di Roma Tor Vergata, Italy.
A
A
Stefani
D J
DJ
Surmeier
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G
Bernardi
D015220:Calcium Channels / Q000187:drug effects; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology*; D066298:In Vitro Techniques; D017072:Neostriatum / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D017465:Receptors, Opioid, delta / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects*
D015220:Calcium Channels; D004745:Enkephalins; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-