Aim: In this study we have investigated the effect of A1-adenosine agonists on the spontaneous motility (s.m.) of rabbit jejunum (RJ) and whether the A1 adenosine acute withdrawal response is controlled by the opioid system as we have seen in guinea pig ileum (GPI). Methods: Segments of jejunum, removed from New Zeland white male rabbit weighing 2-2,5 Kg, were placed in 10 ml tissue bath containing Tyrode solution and maintained at 37°C.; s.m. was measured by an isotonic trasducer. Results: The selective A receptors agonist, N-cyclopenthyl adenosine (CPA; 3-15 x 10-9M) caused a dose-related inhibition (30-100%) of the s.m. amplitude, in some preparations associated with a relaxtion. The addition of the A1 antgonist, 8-cyclopenthyl-1,3-dimethylxantine (CPT, 1,2 x 10-6M) 5 min, after the agonist, elicited in all preparations a withdrawal contracture that consisted in an increase of s.m.or of tone or both. Both the selective k-opioid antagonist nor-binaltorphimine(BNI, 3,4 x 10-8M) and the non selective naloxone (NL, 5,4 x 10-7M) increased the s.m. amplitude and the withdrawal response to the subsequent administration of CPT. Tetrodotoxin ((x 10-8M) inhibited the contraction to CPT.Apamin (5x10-9M) caused a rapid and persistent increase in s.m. amplitude, a reduction of the CPA inhibiting response and of the contraction obtained with CPT. Conclusion: This study demonstrates that following a brief exposure both the A! agonist the RJ exhibits a precipitated contracture as observed with opioids and that the A1 receptor stimulation indirectely activates the opioid system which in turns inhibits the withdrawal response as observed in GPI.

Some characteristics of A1 adenosine-receptor activation on rabbit jejunum spontaneous activity and withdrawal contraction / Martinoli, Lucia; Palmery, Maura; Romanelli, Luca; Tucci, Paolo; Marini, P; Fioravanti, Angelo; Valeri, Pacifico. - In: ACTA PHYSIOLOGICA. - ISSN 1748-1708. - STAMPA. - 188 suppl 652:(2006), pp. 46-46.

Some characteristics of A1 adenosine-receptor activation on rabbit jejunum spontaneous activity and withdrawal contraction

MARTINOLI, Lucia;PALMERY, Maura;ROMANELLI, LUCA;TUCCI, Paolo;FIORAVANTI, Angelo;VALERI, Pacifico
2006

Abstract

Aim: In this study we have investigated the effect of A1-adenosine agonists on the spontaneous motility (s.m.) of rabbit jejunum (RJ) and whether the A1 adenosine acute withdrawal response is controlled by the opioid system as we have seen in guinea pig ileum (GPI). Methods: Segments of jejunum, removed from New Zeland white male rabbit weighing 2-2,5 Kg, were placed in 10 ml tissue bath containing Tyrode solution and maintained at 37°C.; s.m. was measured by an isotonic trasducer. Results: The selective A receptors agonist, N-cyclopenthyl adenosine (CPA; 3-15 x 10-9M) caused a dose-related inhibition (30-100%) of the s.m. amplitude, in some preparations associated with a relaxtion. The addition of the A1 antgonist, 8-cyclopenthyl-1,3-dimethylxantine (CPT, 1,2 x 10-6M) 5 min, after the agonist, elicited in all preparations a withdrawal contracture that consisted in an increase of s.m.or of tone or both. Both the selective k-opioid antagonist nor-binaltorphimine(BNI, 3,4 x 10-8M) and the non selective naloxone (NL, 5,4 x 10-7M) increased the s.m. amplitude and the withdrawal response to the subsequent administration of CPT. Tetrodotoxin ((x 10-8M) inhibited the contraction to CPT.Apamin (5x10-9M) caused a rapid and persistent increase in s.m. amplitude, a reduction of the CPA inhibiting response and of the contraction obtained with CPT. Conclusion: This study demonstrates that following a brief exposure both the A! agonist the RJ exhibits a precipitated contracture as observed with opioids and that the A1 receptor stimulation indirectely activates the opioid system which in turns inhibits the withdrawal response as observed in GPI.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/203675
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