Low-dose apomorphine attenuates morphine-induced enhancement of brain stimulation reward

• Published in: Pharmacology, biochemistry and behavior Vol. 55; no. 1; pp. 87 - 91
• Main Authors: Knapp, Clifford M., Kornetsky, Conan
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.09.1996; Elsevier Science
• Subjects: Animals; Apomorphine - administration & dosage; Apomorphine - pharmacology; Biological and medical sciences; Brain - anatomy & histology; Brain - drug effects; Brain - physiology; Dopamine; Dopamine Agonists - administration & dosage; Dopamine Agonists - pharmacology; Dose-Response Relationship, Drug; Drug toxicity and drugs side effects treatment; Electrodes, Implanted; ICSS; Male; Medical sciences; Miscellaneous (drug allergy, mutagens, teratogens...); Morphine - antagonists & inhibitors; Morphine - pharmacology; Narcotic Antagonists - pharmacology; Narcotics - pharmacology; Pharmacology. Drug treatments; Rats; Rats, Inbred F344; Reward; Self Stimulation - drug effects; Self-stimulation; ICSS; Self-stimulation; Dopamine; Reward; Agonist; Drug combination; Rat; Dopamine receptor; Toxicity; Rodentia; Instrumental conditioning; Morphine; Opiates; Narcotic analgesic; Vertebrata; Mammalia; Acquisition process; Animal; Self stimulation; Reinforcement; Subcutaneous administration; Drug interaction; Mechanism of action
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/0091-3057(96)00073-1

Thresholds for brain stimulation reward (BSR) delivered to the medial forebrain bundle-lateral hypothalamus were determined by means of a rate free psychophysical method. Lower doses of apomorphine (0.5 to 0.2 mg/kg) produced modest elevations in BSR thresholds. A 0.4 mg/kg dose of apomorphine resulted in emergence of Stereotypic behaviors and the loss of stimulus control. Morphine's BSR threshold lowering effects were significantly blocked by the concurrent administration of a 0.1 mg/kg dose of apomorphine. These results support the hypothesis that presynaptic dopamine neurons are involved in the mediation of morphine's reinforcing effects and that dopamine autoreceptor agonists may be of some use in the pharmacotherapy of opiate abuse.