Further Studies of the Effects of Intranigral Morphine on Behavioral Responses to Noxious Stimuli
Bilateral intranigral microinjection of morphine produces dose-related and naloxone reversible analgesic-like effects on the hot-plate and tail-flick tests. The main objectives of the present studies were to further characterize the analgesic-like effects of intranigral morphine, to determine whether these effects were related to a general impairment of sensory or motor function, and to assess their anatomical specificity. The principal findings are: (1) intranigral morphine (10 μg) suppresses pain-related behavior without altering responses to a variety of non-noxious auditory, visual, and somatic stimuli, and without producing motor impairment; (2) movement of injector needles approximately 1 mm rostral, dorsal, or medial to the active nigral site significantly reduces the analgesic-like effect of morphine on the tail-flick test; and (3) electrolytic lesions confined to the nigra significantly reduced the analgesic-like effect of morphine on the hot-plate test. It is concluded that the analgesic-like effects of intranigral morphine are mediated by the substantia nigra and that these effects are specifically related to pain.
Waguespack, A. M.,
Baumeister, A. A.,
Hawkins, M. F.,
Chatellier, M. O.
(1990). Further Studies of the Effects of Intranigral Morphine on Behavioral Responses to Noxious Stimuli. Brain Research, 525(1), 115-125.
Available at: https://nsuworks.nova.edu/cps_facarticles/222