title: Circling from intracranial morphine applied to the ventral tegmental area in rats.
abstract: Crystalline morphine applied unilaterally to the ventral tegmental area in rats caused circling away from the side of application. This circling was reversed by naloxone (3 mg/kg) and blocked by pretreatment with pimozide (0.5 mg/kg). When tested in an open field the animals followed the perimeter of the enclosure; thus the radius of the circles described was determined by environmental rather than central factors. Morphine induced forward locomotion in all four limbs; there were no major signs of postural asymmetry noted in the longitudinal axis of the animal's body. This study suggests that morphine activates a population of A-10 dopamine cells known to be involved in locomotion.
mesh_terms: D000818:Animals; D001931:Brain Mapping; D004298:Dopamine / Q000502:physiology*; D004347:Drug Interactions; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D009270:Naloxone / Q000008:administration & dosage; D010868:Pimozide / Q000008:administration & dosage; D051381:Rats; D011919:Rats, Inbred Strains; D013681:Tegmentum Mesencephali / Q000187:drug effects*
chemical_list: D010868:Pimozide; D009270:Naloxone; D009020:Morphine; D004298:Dopamine