BNTX maleate

Pharmacological evidence for a 7-benzylidenenaltrexone-preferring opioid receptor mediating the inhibitory actions of peptidic delta- and mu-opioid agonists on neurogenic ion transport in porcine ileal mucosa.[Pubmed:11303057]

J Pharmacol Exp Ther. 2001 May;297(2):672-9.

The antidiarrheal and constipating effects of opiates are partly attributed to reductions in active anion secretion across the intestinal mucosa that are modulated by submucosal neurons. In this study, the opioid receptor mediating the actions of opioids on ion transport was characterized in mucosa-submucosa sheets from porcine ileum. Electrical transmural stimulation evoked transient increases in short-circuit current, an electrical measure of neurogenic ion transport, in this preparation. After serosal addition, the peptidic delta-opioid agonists [D-Ala(2)]-deltorphin II (pIC(50) = 8.4 +/- 0.7), [D-Ala(2),D-Leu(5)]-enkephalin (DADLE), [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE), and [D-Ser(2),Leu(5),Thr(6)]-enkephalin (DSLET), and the mu-opioid agonists [D-Ala(2),N-methyl-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) (pIC(50) = 8.0 +/- 0.1), endomorphin I, and PL-017 inhibited short-circuit current elevations. Nonpeptidic mu- or delta-opioid agonists (morphine, loperamide, and SNC80) and kappa-opioid agonists (U-50,488H and U-69,593) were <360-fold less potent than deltorphin II. At 100 nM, the delta(1)-opioid antagonist 7-benzylidenenaltrexone reduced the potencies of DPDPE and DAMGO by 13.5- and 15.5-fold, respectively; at an identical concentration naltriben, a delta(2)-opioid antagonist, or the mu-opioid antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP) reduced DPDPE potency by 4.1- and 3.4-fold, respectively, but had no significant effect on DAMGO potency. Using primary antisera directed toward cloned opioid receptors, delta-opioid receptor immunoreactivity was immunohistochemically localized in submucosal neurons and nerve fibers, but immunoreactivities to kappa- or mu-opioid receptors were not detected in the mucosa-submucosa. These results suggest that a novel 7-benzylidenenaltrexone-sensitive opioid receptor is expressed in submucosal neurons of the porcine ileum, which mediates the inhibitory effects of peptidic mu- and delta-opioid agonists on neurogenic ion transport.

Antinociception and delta-1 opioid receptors in the rat spinal cord: studies with intrathecal 7-benzylidenenaltrexone.[Pubmed:7562504]

J Pharmacol Exp Ther. 1995 Sep;274(3):1317-24.

As part of the continuing investigation of the role of spinal delta opioid receptors in antinociception, this study characterized the ability of 7-benzylidenenaltrexone (BNTX), a selective delta-1 opioid receptor antagonist, to antagonize the antinociception produced in the rat by intrathecal (i.t.) administration of the respective delta-1 and delta-2 opioid receptor agonists, DPDPE and [D-Ala2, Glu4]deltorphin (DELT), or the mu receptor agonist DAMGO. In the tail flick test, 10-min pretreatment with 1 microgram of BNTX, increased the ED50 value of DPDPE from 27.5 micrograms (42.6 nmol) to 114.8 micrograms (177.8 nmol), but did not increase the ED50 values of either DELT or DAMGO. Increasing the dose of BNTX to 3 micrograms did not produce a significantly greater antagonism of the antinociceptive effects of DPDPE and did not antagonize the antinociceptive effects of DAMGO. However, it did enhance the antinociceptive effects of DELT decreasing its ED50 from 5.3 to 0.18 micrograms in the tail flick test. In the hot plate test, 10 min pretreatment with 1 microgram of BNTX selectively antagonized the antinociceptive effects of DPDPE, but did not antagonize the actions of DAMGO or DELT. Increasing the dose of BNTX to 3 micrograms also did not produce a significantly greater antagonism of the antinociceptive effects of DPDPE in the hot plate test, but did antagonize both the increase in hot plate latency and the modest decrement in motor function produced by 30 micrograms i.t. of DELT. However, the antagonism of these effects of DELT occurred much later in time than BNTX's antagonism of the antinociceptive effects of DPDPE.

A highly selective delta 1-opioid receptor antagonist: 7-benzylidenenaltrexone.[Pubmed:1327826]

Eur J Pharmacol. 1992 Jul 21;218(1):195-6.

In guinea pig brain membranes 7-benzylidenenaltrexone (BNTX) possesses 100-fold greater affinity (Ki = 0.1 nM) for [3H]DPDPE [3H][D-Pen2,D-Pen5]enkephalin) binding sites (delta 1) relative to those of [3H]DSLET ([3H][D-Ser2,Leu5]enkephalin-Thr6) (delta 2). The ED50 dose ratio (tail flick) in mice for the antagonism of DPDPE-induced antinociception of BNTX (6.3 pmol i.c.v.) was 7.2, whereas for DSLET, morphine and U69593 it was not significantly different from unity. The fact that there was no correlation of the binding or in vivo data for BNTX with antagonist potency in smooth muscle preparations suggests that the in vitro pharmacologic activity is mediated by delta-opioid subtypes that are different from those in the brain.