title: Sensitization by ventral pallidal DAMGO:  lack of cross-sensitization to morphine.
abstract: Repeated injections of morphine into the ventral pallidum of laboratory rats results in the development and expression of motor sensitization. Although morphine and [D-Ala, N-MePhe, Gly(ol)]-enkephalin (DAMGO) both activate μ-opioid receptors, their influence on receptor-mediated signaling differs; therefore, we determined if they differentially influenced ventral pallidal-mediated motor sensitization. Repeated intraventral pallidal injections of DAMGO led to the development of motor sensitization and this behavior persisted for at least 18 days. When DAMGO-sensitized rats were challenged with a morphine treatment (either in the ventral pallidum or systemically), the resulting motor response was similar to that seen in rats with a history of intrapallidal saline, that is, cross-sensitization did not occur. As DAMGO and morphine likely activate different arms of the heterologous signal transduction system associated with μ-opioid receptors, these observations may reflect behavioral consequences of biased agonism at these receptors.
authors: Neuroscience Program, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA.
authors: Sandra L
authors: SL
authors: Rokosik
authors: Amanda L
authors: AL
authors: Persons
authors: T Celeste
authors: TC
authors: Napier
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004333:Drug Administration Routes; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology*; D005917:Globus Pallidus / Q000187:drug effects*; D006948:Hyperkinesis / Q000139:chemically induced* / Q000503:physiopathology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000701:Analgesics, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009020:Morphine