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Opioid regulation of intracellular free calcium in cultured mouse dorsal root ganglion neurons
Author(s) -
Tang T.,
Stevens B.A.,
Cox B.M.
Publication year - 1996
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(19960515)44:4<338::aid-jnr4>3.0.co;2-d
Subject(s) - dorsal root ganglion , dorsum , calcium in biology , calcium , intracellular , opioid , neuroscience , microbiology and biotechnology , ganglion , chemistry , biology , anatomy , biochemistry , receptor , organic chemistry
Opioid agonists induced an increase in the intracellular free calcium concentration ([Ca 2+ ] i ) or an inhibition of K + (25 mM)‐stimulated increase in [Ca 2+ ] i in different subsets of mouse dorsal root ganglion (DRG) neurons. The total neuronal population was grouped into three classes according to somatic diameter and defined as small (<16 μm), intermediate (16–25 μm), or large (>25 μm) neurons. Substance P‐like immunoreactivity was detected mainly in the small and intermediate neurons. The δ, κ, and μ opioid receptor agonists [D‐Ser 2 , Leu 5 ]enkephalin‐Thr (DSLET), U69593, and [D‐Ala 2 , MePhe 4 , Gly‐ol 5 ]enkephalin (DAMGO) each induced a transient increase in [Ca 2+ ] i in a small fraction (<30%) of neurons. The increases in [Ca 2+ ] i were blocked by the opioid antagonist naloxone. The dihydropyridine‐sensitive calcium channel blocker nifedipine also blocked the increase in [Ca 2+ ] i induced by 1 μM DSLET. The rank order of potency (percentage of cells responding to each opioid agonist) was DSLET > U69593 > DAMGO. The opioid‐induced increase in [Ca 2+ ] i was observed mainly in large neurons, with a low incidence in small and intermediate neurons. Opioid agonists also caused inhibition of K + ‐stimulated increases in [Ca 2+ ] i , which were blocked by naloxone (1 μM). Inhibition of the K + ‐stimulated increase by 1 μM DSLET or U69593 was greater in small and intermediate neurons than in large neurons. © 1996 Wiley‐Liss, Inc.