Conditional hypoalgesia is attenuated by naltrexone applied to the periaqueductal gray. Brain Res 1990 Dec 24;537(1-2):88-92
Date
12/24/1990Pubmed ID
1964843DOI
10.1016/0006-8993(90)90343-aScopus ID
2-s2.0-0025695879 (requires institutional sign-in at Scopus site) 75 CitationsAbstract
The ventrolateral periaqueductal gray (vPAG) is an important component in a brainstem system involved in the endogenous modulation of nociception and defensive behavior. The present study was conducted to determine if opioid receptors within the vPAG contribute to the hypoalgesia seen in rats during presentation of a Pavlovian CS for footshock. Independent groups of animals received microinjections of either 5.0 micrograms naltrexone HCl or vehicle into the vPAG prior to being placed in an observation chamber in which shock had been delivered 24 h earlier. Nociceptive reactivity was measured with the formalin test. Naltrexone treatment attenuated conditional hypoalgesia but did not affect formalin-induced behavior in non-shocked rats. Naltrexone had no effect on the amount of defensive freezing behavior observed during the test session. These results indicate that conditional hypoalgesia as measured by the formalin test involves the activation of documented brainstem antinociceptive systems.
Author List
Helmstetter FJ, Landeira-Fernandez JAuthor
Fred Helmstetter PhD Professor in the Psychology / Neuroscience department at University of Wisconsin - MilwaukeeMESH terms used to index this publication - Major topics in bold
AnimalsBehavior, Animal
Conditioning, Operant
Electroshock
Female
Formaldehyde
Microinjections
Naltrexone
Pain
Periaqueductal Gray
Rats
Receptors, Opioid