Nigral 6-hydroxydopamine lesions equally decrease mu and delta opiate binding to striatal patches: further evidence for a conformationally malleable type 1 opiate receptor.
We have investigated the effect of nigral 6-hydroxydopamine (6-OHDA) lesions on binding of the mu receptor ligand dihydromorphine (DHM) and the delta receptor ligand [D-Ala2, D-Leu5]-enkephalin (DADLE) to sections of rat striatum under conditions which yield mu-like and delta-like ligand selectivities at discrete receptor patches (Type 1 receptor). 3H-DHM binding was decreased 43% while 3H-DADLE was decreased 22%. However, when the contribution of diffuse binding (Type 2) which is not affected by 6-OHDA is subtracted from the patch, the decrease is approximately 49% for both ligands. These data support the hypothesis that the Type 1 receptor of striatal patches is a conformationally malleable receptor entity which can exist in states having high affinities for various classes of opiate ligands.
D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism*; D004090:Dihydromorphine / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D006892:Hydroxydopamines / Q000494:pharmacology*; D008297:Male; D009294:Narcotics / Q000378:metabolism*; D016627:Oxidopamine; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism*; D013378:Substantia Nigra / Q000502:physiology*
D006892:Hydroxydopamines; D009294:Narcotics; D011957:Receptors, Opioid; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D016627:Oxidopamine; D004090:Dihydromorphine