Self-administration of small amounts of morphine through glass micropipettes into the ventral tegmental area of the rat.
A micropipette-system was used to investigate intracranial self-injection of morphine in the rat. The system consisted of a glass micropipette (tip dia 5 microns) connected by flexible tubing and a swivel to a pressure source. Using nose-poking through a hole in one wall of the cage as the operant, rats self-injected quantities as small as 50 ng/5 nl of morphine into the ventral tegmental area. In contrast, rats in the saline-treated group and yoked-control group did not increase their rates of nose-poking behaviour above baseline levels. Intermittent reinforcement in the morphine-treated group resulted in a further increase in the rate of nose-poking. Histological inspection of the site of injection revealed minimal damage to brain tissue and likely confinement of the injected solution to the area around the tip of the pipette.
Welzl
H
H
Institute of Physiological Psychology, University of Düsseldorf, Federal Republic Germany.
Kuhn
G
G
Huston
J P
JP
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D008297:Male; D008845:Microinjections; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012646:Self Administration; D013681:Tegmentum Mesencephali / Q000033:anatomy & histology / Q000502:physiology*
D009020:Morphine