Ar. Tome et al., Naloxone inhibits nicotine-induced receptor current and catecholamine secretion in bovine chromaffin cells, BRAIN RES, 903(1-2), 2001, pp. 62-65
Nicotine-induced catecholamine (CA) secretion and inward ionic currents wer
e inhibited by the opioid antagonist naloxone in cultured bovine chromaffin
cells. Naloxone inhibited nicotine-induced CA secretion, as detected by an
on-line real-time electrochemical technique, in a dose-dependent manner (I
C50=29 muM). In voltage-clamped chromaffin cells, nicotine (10 muM) evoked
on average peak inward current of -146 pA that was inhibited by low concent
rations of naloxone ( 42% at 0.1 muM). The antagonist also inhibited total
charge influx associated with nicotinic receptor activation (53% at 0.1 muM
). This provides strong evidence that naloxone modulation of nicotine-induc
ed CA secretion does not involve opioid receptors but results from the dire
ct interaction with the nicotinic receptor itself, which might also be the
case for other related opioid compounds. (C) 2001 Elsevier Science B.V. All
rights reserved.