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Differential Regulation of D 1 Dopamine Receptor‐ and of A 2a Adenosine Receptor‐Stimulated Adenylyl Cyclase by μ‐, δ 1 ‐, and δ 2 ‐Opioid Agonists in Rat Caudate Putamen
Author(s) -
Noble Florence,
Cox Brian M.
Publication year - 1995
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1995.65010125.x
Subject(s) - adenylyl cyclase , damgo , medicine , adenosine , chemistry , endocrinology , adcy9 , dopamine receptor d2 , dopamine , agonist , opioid receptor , receptor , biology
Inhibition and stimulation of adenylyl cyclase by opioid and D 1 dopamine or A 2a adenosine agonists, respectively, were characterized in the caudate putamen of rats. D 1 dopamine receptors have been reported to be localized preferentially on striatonigral neurons and A 2a adenosine receptors on striatopallidal neurons. The aim of the present study was to evaluate the effects of μ‐[Tyr‐ d ‐Ala‐Gly‐( N ‐Me)Phe‐Gly‐ol (DAMGO)], δ 1 ‐[Tyr‐ d ‐Pen‐Gly‐Phe‐ d ‐Pen (DPDPE)], and δ 2 ‐ ([ d ‐Ala 2 ]deltorphin‐II [DT‐II]) opioid agonists on the D 1 dopamine receptor‐ and A 2a adenosine receptor‐stimulated adenylyl cyclase in membranes from rat caudate putamen. The results show that DAMGO, DPDPE, and DT‐II inhibit forskolin‐stimulated adenylyl cyclase [selectively antagonized by d ‐Phe‐Cys‐Tyr‐ d ‐Trp‐Orn‐Thr‐Pen‐Thr‐NH 2 (CTOP; μ antagonist), 7‐benzylidenenaltrexone (BNTX; δ 1 antagonist), and naltriben (NTB; δ 2 antagonist), respectively], but only μ‐ and δ 2 ‐opioid agonists inhibit D 1 dopamine‐stimulated adenylyl cyclase (antagonized by CTOP and NTB, respectively). Furthermore, DT‐II and DPDPE inhibit A 2a adenosine‐stimulated adenylyl cyclase (antagonized by NTB and BNTX, respectively), whereas DAMGO did not inhibit A 2a adenosine‐stimulated adenylyl cyclase activity. These results suggest that μ‐, δ 1 ‐, and δ 2 ‐opioid receptors display differential localization and provide neurochemical evidence suggesting the differential location of the δ 1 and δ 2 subtypes. μ‐Opioid receptors may be preferentially expressed by striatonigral neurons, δ 1 ‐ by striatopallidal neurons, and δ 2 ‐ by these two striatal efferent neuron populations.