A selective .delta.1 opioid receptor agonist derived from oxymorphone. Evidence for separate recognition sites for .delta.1 opioid receptor agonists and antagonists

1993 ◽  
Vol 36 (17) ◽  
pp. 2572-2574 ◽  
Author(s):  
P. S. Portoghese ◽  
S. T. Moe ◽  
A. E. Takemori
Keyword(s):  
Opioid Receptor ◽  
Receptor Agonist ◽  
Receptor Agonists ◽  
Recognition Sites ◽  
Opioid Receptor Agonist ◽  
Opioid Receptor Agonists ◽  
Receptor Agonists And Antagonists

Differential Effects of μ-, δ-, and κ-Opioid Receptor Agonists on Mechanosensitive Gastric Vagal Afferent Fibers in the Rat

2000 ◽  
Vol 83 (4) ◽  
pp. 2209-2216 ◽  
Author(s):  
Noriyuki Ozaki ◽  
J. N. Sengupta ◽  
G. F. Gebhart
Keyword(s):  
Opioid Receptor ◽  
Receptor Agonist ◽  
Dose Range ◽  
Receptor Agonists ◽  
Afferent Fibers ◽  
Opioid Receptor Agonist ◽  
Resting Activity ◽  
Vagal Afferent ◽  
Δ Opioid Receptor ◽  
Opioid Receptor Agonists

Single-fiber recordings were made from the decentralized right cervical vagus nerve (hyponodosal) of the rat. A total of 56 afferent fibers that responded to gastric distension (GD) were studied: 6 fibers were stimulated by phasic balloon GD, 50 by fluid GD. All fibers gave increasing responses to increasing pressures of GD (5–60 mmHg). The effects of μ-opioid (morphine), δ-opioid (SNC80), and κ-opioid (EMD61,753, U62,066) receptor agonists were tested on responses of afferent fibers to GD. Morphine, administered systemically over a broad dose range (10 μg to 31 mg/kg, cumulative), had no effect on either resting activity or responses of vagal afferent fibers to GD. Similarly, the δ-opioid receptor agonist SNC80 (0.05–3.2 mg/kg) did not affect resting activity or responses to GD. In contrast, cumulative intra-arterial doses of the κ-opioid receptor agonist EMD61,753 or U62,066 dose dependently attenuated afferent fiber responses to GD. Doses producing inhibition to 50% of the control response to GD of EMD61,753 (8.0 mg/kg) and U62,066 (8.8 mg/kg) did not differ. The effect of U62,066 was moderately attenuated by a nonselective dose (4 mg/kg) of naloxone hydrochloride; the κ-opioid receptor-selective antagonist nor-BNI (20 mg/kg) was ineffective. These results demonstrate that κ-, but not μ- or δ-opioid receptor agonists modulate visceral sensation conveyed by vagal afferent fibers innervating the stomach. Given that κ-opioid receptor agonists effects were only modestly antagonized by naloxone and not at all by nor-BNI, the results point to a novel site of action.

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