Results are expressed as d.p.m.?g?1 of wet weight tissue. than PER (4.3 and 1.6 occasions). DPDPE experienced a lower potency than -agonists in all experiments, Col003 and no dose-response could be obtained after s.c. administration on GIT. Pretreatment with i.c.v. Abdominal muscles (24?h) or antisense ODN (5 days), decreased the effects (GIT and PER) of i.c.v. morphine and fentanyl, while those Bmpr2 of DPDPE remained unchanged. The Abdominal muscles did not alter the peripheral effects of -opioids. The results show that (i.c.v. or s.c.) opioids produce dose-related inhibitions of PER and GIT, being more potent by the i.c.v. route. Delta-opioids had a greater effect on PER than GIT, while the reverse occurred for -agonists. Pretreatment with Abdominal muscles or ODN to -OR, blocked the central effects of (but not ) agonists on GIT and PER. and (Wahlested em et al /em ., 1993). Thus, the i.c.v. administration of antisera generated against the amino-terminal portion or the peptide sequence of the second extracellular loop of the cloned -OR, decreases the antinociceptive effects of -specific opioid agonists in mice (Garzn & Snchez-Blzquez, 1995). Similarly, the i.c.v. administration of ODNs targeting specific regions of mRNA for the -OR, also block the supraspinal antinociceptive effects of morphine (Rossi em et al /em ., 1994; Snchez-Blzquez em et al /em ., 1997), while random sequences ODN are inactive. In addition, Col003 ODNs have been reported to block opioid induced inhibition of GIT in mice (Rossi em et al /em ., 1995). The inhibitory effects of systemic opioids on gastrointestinal function, are mediated by OR located at central (CNS) and peripheral sites (gut) (Shook em et al /em ., 1987). In mice, inhibition of GIT by opioids is usually produced by binding predominately to and -OR (Porreca em et al /em Col003 ., 1984; Pol em et al /em ., 1994) located at both sites; however, the precise implication of each anatomical site is not well established. Other intestinal effects of opioids such as the inhibition of water and electrolyte permeability have not been completely characterized. The primary aim of our investigation was to characterize the effects of and opioid agonists on intestinal PER and their predominant site of action (central vs peripheral). In addition, we wanted to determine if the i.c.v. administration of specific -OR Abdominal muscles or antisense ODN to -OR, could reverse the effects of agonists on GIT and intestinal PER. Methods Animals Experiments were performed in male Swiss CD-1 mice, weighting 20C25?g. Animals were housed under 12?h light and 12?h dark conditions in a room with controlled temperature (22C) and humidity (66%). Animals had free access to food and water and were allowed to become acclimated to their housing conditions for any least 1 week before the study. All experiments were conducted between 09.00?h and 14.00?h. The study protocol was approved by the local Committee of Animal Use and Care of our Institution and in accordance Col003 with the guidelines of European Community on Care and Use of Laboratory Animals. Gastrointestinal transit (GIT) Gastrointestinal transit was measured according to the procedures used in our laboratory (Pol em et al /em ., 1996b; Puig em et al /em ., 1996). Briefly, food was removed 18?h before the experiment but animals had free access to water. At this time, a charcoal meal (0.25?ml of 10% charcoal in 5% gum acacia) was administered intragastrically and GIT was evaluated 20?min later. Animals were then sacrificed and the small intestine separated from omentum avoiding stretching. The length of intestine from your pyloric sphincter to the ileocecal junction, and the distance travelled by Col003 the charcoal, were measured. For each animal, GIT was calculated as the percentage (%) of distance travelled by the charcoal, relative to the total length of the small intestine (% of GIT). Intestinal permeability (PER) Permeability of the small intestine was assessed by measuring the passage of a radioactive marker (51Cr-EDTA) from blood to lumen, using a technique adapted from Miller em et al /em . (1991). Prior to the study, mice were fasted for 18?h except for free access to water. A laparotomy was performed under light ether anaesthesia, and both renal pedicles ligated to prevent rapid excretion of the radioactive marker into the urine. Animals were allowed to recover for a period of 50?min, and at this time 4? Ci of 51Cr-EDTA were injected intravenously in a vein of the tail. Forty minutes later, the small intestine was removed and the intestinal.

Results are expressed as d