Skip to main content
padlock icon - secure page this page is secure

Effects Of Endomorphin-1 And -2 On μ-Opioid Receptors In Myenteric Neurons And In The Peristaltic Reflex In Rat Small Intestine

Buy Article:

$52.00 + tax (Refund Policy)

SUMMARY

1. The aim of the present investigations was to characterize the effect of endomorphins on the function of rat small intestine smooth muscle and on the electrically induced ascending and descending reflex pathway of rat small intestine in vitro.

2. Endomorphin-1 and -2 left the basal tonus and the pharmacologically stimulated smooth muscle unchanged. In contrast, electrically induced twitch contractions were significantly reduced by endomorphin-1 and -2 and this reduction was reversed by the μ-opioid receptor antagonist Cys-Tyr-Orn-Pen-amide (CTOP), suggesting a specific μ-opioid receptor-mediated effect on neural tissue.

3. In the reflex model, endomorphin-1 caused a significant inhibition (IC50 2.3 × 10–8 mol/L) of the ascending contraction (10–8 mol/L: –28.3 ± 5.8%; 10–7 mol/L: –94.7 ± 0.2.8%; both P < 0.05; n = 7). Descending relaxation increased at a concentration of 10–8 mol/L endomorphin-1 (+61.6 ± 24.5%; 10–7 mol/L: +237.0 ± 65.4%; both P < 0.05; n = 6).

4. Endomorphin-1 caused a further significant increase in the latency of the ascending contraction (10–8 mol/L: +44.7 ± 20.5%; 10–7mol/L: +93.5 ± 16.1%; both P < 0.05; n = 7), whereas the latency of the descending relaxation was unaltered (n = 7). Similar results were observed for endomorphin-2.

5. All effects could be reversed by a wash-out afterwards and were blocked by pre-incubation with CTOP (10–6 mol/L).

6. Reverse transcription–polymerase chain reaction demonstrated mRNA expression of μ-opioid receptors in the rat ileum longitudinal muscle/myenteric plexus preparation, as well as in the oesophagus and stomach.

7. Endomorphin-1 and -2 reduce the cholinergic-induced contractile response of the rat ileal smooth muscle preparation via a presynaptic mechanism.

8. By a specific and reversible interaction with μ-opioid receptors, the ascending excitatory and descending inhibitory reflex responses were attenuated or facilitated, respectively.

9. In conclusion, the endomorphins may be the physiological endogenous μ-opioid receptor agonists in the rat small intestine.
No References
No Citations
No Supplementary Data
No Article Media
No Metrics

Keywords: endomorphin-1; endomorphin-2; peristaltic reflex; μ-opioid receptors

Document Type: Research Article

Affiliations: II Medizinische Klinik und Poliklinik der TU München, München, Germany

Publication date: May 1, 2002

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more