Abstract
Summaryo1)Responsiveness of guinea-pig ileal longitudinal smooth muscie-myenteric plexus preparations to drugs activating GABA-B receptors was studied in morphine-tolerant animals. For this purpose morphine pellets (75 mg each) were implanted subcutaneously in guinea-pigs and experiments were performed three days later in electrically-stimulated ileal strips.2)Activation of GABA-B receptors with GABA (10-6-10-3 M) or (-)-baclofen (10-6-10-3 M) caused a dose-related inhibition of twitch response that was about 80% lower in preparations from morphine-tolerant animals than in controls. This was found both in preparations maintained in the presence of morphine (10-6 M) and in morphine-free Krebs. The effect was evident also in ileal preparations from morphine-tolerant animals in which a withdrawal syndrome was induced by the administration of naloxone before sacrifice.3)The phenomenon was specific since the dose-response curve of the adenosine-inhibitory effect was comparable in preparations from tolerant animals and controls.4)The hyporesponsiveness to GABA-B receptor activation began 12 h after pellet implantation and was maximal on the third day.5)It is concluded that during tolerance to and withdrawal from morphine there is a hyporesponsiveness of GABA-B receptors in "in vitro" guinea-pig ileal longitudinal muscle-myenteric plexus preparations.
| Original language | English |
|---|---|
| Pages (from-to) | 773-783 |
| Number of pages | 11 |
| Journal | Pharmacological Research Communications |
| Volume | 20 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 1988 |
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ASJC Scopus subject areas
- Pharmacology
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Decreased response to GABA-B agonists in longitudinal smooth muscle-myenteric plexus preparations from morphine-tolerant guinea-pigs. / Luzzi, S.; Franchi-Micheli, S.; Ciuffi, M.; Gori, Ann Maria; Gentilini, Grazia; Zilletti, Lucilla.
In: Pharmacological Research Communications, Vol. 20, No. 9, 1988, p. 773-783.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Decreased response to GABA-B agonists in longitudinal smooth muscle-myenteric plexus preparations from morphine-tolerant guinea-pigs
AU - Luzzi, S.
AU - Franchi-Micheli, S.
AU - Ciuffi, M.
AU - Gori, Ann Maria
AU - Gentilini, Grazia
AU - Zilletti, Lucilla
PY - 1988
Y1 - 1988
N2 - Summaryo1)Responsiveness of guinea-pig ileal longitudinal smooth muscie-myenteric plexus preparations to drugs activating GABA-B receptors was studied in morphine-tolerant animals. For this purpose morphine pellets (75 mg each) were implanted subcutaneously in guinea-pigs and experiments were performed three days later in electrically-stimulated ileal strips.2)Activation of GABA-B receptors with GABA (10-6-10-3 M) or (-)-baclofen (10-6-10-3 M) caused a dose-related inhibition of twitch response that was about 80% lower in preparations from morphine-tolerant animals than in controls. This was found both in preparations maintained in the presence of morphine (10-6 M) and in morphine-free Krebs. The effect was evident also in ileal preparations from morphine-tolerant animals in which a withdrawal syndrome was induced by the administration of naloxone before sacrifice.3)The phenomenon was specific since the dose-response curve of the adenosine-inhibitory effect was comparable in preparations from tolerant animals and controls.4)The hyporesponsiveness to GABA-B receptor activation began 12 h after pellet implantation and was maximal on the third day.5)It is concluded that during tolerance to and withdrawal from morphine there is a hyporesponsiveness of GABA-B receptors in "in vitro" guinea-pig ileal longitudinal muscle-myenteric plexus preparations.
AB - Summaryo1)Responsiveness of guinea-pig ileal longitudinal smooth muscie-myenteric plexus preparations to drugs activating GABA-B receptors was studied in morphine-tolerant animals. For this purpose morphine pellets (75 mg each) were implanted subcutaneously in guinea-pigs and experiments were performed three days later in electrically-stimulated ileal strips.2)Activation of GABA-B receptors with GABA (10-6-10-3 M) or (-)-baclofen (10-6-10-3 M) caused a dose-related inhibition of twitch response that was about 80% lower in preparations from morphine-tolerant animals than in controls. This was found both in preparations maintained in the presence of morphine (10-6 M) and in morphine-free Krebs. The effect was evident also in ileal preparations from morphine-tolerant animals in which a withdrawal syndrome was induced by the administration of naloxone before sacrifice.3)The phenomenon was specific since the dose-response curve of the adenosine-inhibitory effect was comparable in preparations from tolerant animals and controls.4)The hyporesponsiveness to GABA-B receptor activation began 12 h after pellet implantation and was maximal on the third day.5)It is concluded that during tolerance to and withdrawal from morphine there is a hyporesponsiveness of GABA-B receptors in "in vitro" guinea-pig ileal longitudinal muscle-myenteric plexus preparations.
UR - http://www.scopus.com/inward/record.url?scp=0023819891&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0023819891&partnerID=8YFLogxK
U2 - 10.1016/S0031-6989(88)80716-1
DO - 10.1016/S0031-6989(88)80716-1
M3 - Article
C2 - 2845451
AN - SCOPUS:0023819891
VL - 20
SP - 773
EP - 783
JO - Pharmacological Research
JF - Pharmacological Research
SN - 1043-6618
IS - 9
ER -