Biomedical subjects

R W Barrett

Publications and source records attributed to R W Barrett.

39 records · Page 3Linked to original sources

PubMed1983

Comparison of the filtration and centrifugation methods for assaying [3H](D-ala2, D-leu5)enkephalin binding to mouse brain membranes.

The binding of [3H](D-ala2, D-leu5)enkephalin (DADLE) to mouse brain membranes was studied via rapid filtration with GF/C filters and via the centrifugation method. The amount of specific binding determined by filtration was found to be dependent on the length of time between the initiation of vacuum and the actual time of filtration. Vacuum strength alone also significantly affected the amount of specifically bound [3H]DADLE measured by filtration. The centrifugation method increased the number of experimentally determined binding sites when compared to the filtration method. The difference in the number of binding sites was only partially attributable to passage of binding material through the GF/C filter. The ability of morphine to displace [3H]DADLE was also found to differ slightly between the two methods. These data indicate that centrifugation is a better method of determining the binding parameters of [3H]DADLE in mouse brain membrane preparations.

Animals↗

PubMed1983

Multidimensional analysis of ligand binding data: application to opioid receptors.

The existence of distinct mu and delta opioid receptors is now well accepted. Most investigators favor the hypothesis that these receptors are physically distinct and that the enkephalins are only 2-10 fold selective for the delta receptor. Rothman and Westfall (Mol. Pharmacol. 21:548-557) recently challenged this hypothesis, proposing that at least some population of mu and delta receptors coexist in an opioid receptor complex and that the enkephalins are at least 100 fold selective for the delta receptor. In this paper we describe a generally applicable method we have used to design and analyze ligand binding experiments which distinguish between the two different models.

Animals↗

PubMed1982

The effects of receptor selective opioid peptides on morphine-induced analgesia.

Utilizing the mouse tail-flick assay, four opioid peptides, which have been reported to be selective for either mu- or delta-opioid receptors, were examined for their analgesic potency and for their ability to modify morphine-induced analgesia. [D-Ala2,D-Leu5]enkephalin and [D-Ser2,Thr6]leucine-enkephalin, putative delta-receptor selective peptides, produced a potent analgesic response and at subanalgesic doses potentiated morphine-induced analgesia. Morphiceptin and [D-Ala2,Pro5]enkephalinamide, putative mu-receptor selective peptides, were similarly found to produce analgesia. However, in contrast to the delta-receptor selective peptides, three mu-receptor selective peptides were unable to alter the potency of morphine. Thus, it would appear that the potentiation of morphine analgesia is a unique property of delta-receptor selective peptides.

Analgesia↗