Locomotor activity and one-way active avoidance after intrahyppocampal injection of neurotransmitter antagonists

ABSTRACT

Sixty-three rats with previous training in a T-maze, bilaterally implanted with cannulae directed toward the dorsal hippocampus, were used in this study. All rats received bilateral 1-microngl injections 20 min before testing for locomotor activity (day 1) and one-way active avoidance (day 3). The following drugs were injected into groups of 4 to 8 animals scopolamine (9 or 18 microng/micronl), propranolol (5 or 10 microng/micronl), cimetidine (0.75 or 1.5 microng/micronl), sulpiride (5 or 10 microng/micronl), or vehicle (Krebs-ringer). Locomotor activity was not changed by injection of any drug. However, intrahippocampal injections of scolpolamine (9 microng/micronl) and sulpiride (10 microng/micronl) impoaired avoidance bahavior, particularly during the last five trials of the task. We conclude that muscarinic-cholinergic and D2-dopaminergic, but not beta-adrenergic or H2-histaminergic, mechanisms in the hippocampus are involved in the performance of one-way active avoidance behavior