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  • Neurotensin  (2)
  • Amphetamine  (1)
  • Exploration  (1)
  • Analgesia
  • 1985-1989  (3)
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  • 1
    ISSN: 1432-2072
    Keywords: Neurotensin ; Ventral mesencephalon ; Investigatory behaviour ; Motor behavior ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present experiments examined in detail the behavioral response to microinfusions of neurotensin (NT) into the ventral tegmental area (VTA), substantia nigra (SN) and hippocampus (HPC). The behavioral apparatus consisted of an eight-hole box in which investigatory and spontaneous motor behavior were recorded. Three doses (0.175, 0.5, 4.0 μg) of NT were injected into the VTA. The main effect of NT was a strong augmentation of rearing (frequency and duration) both in the periphery and center of the arena, accompanied by a small increase in locomotion and decreased grooming. NT had no effect on the strategy, organization, or duration of exploration but did augment frequency of hole visits towards the end of the session. NT injected into the SN and HPC had no effect on investigatory and spontaneous behavior with the exception of an increase in peripheral locomotion after HPC-NT injections. The results are discussed in terms of a modulatory role of endogenous NT on mesolimbic dopamine neurons.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Amphetamine ; Apomorphine ; Dopamine ; Exploration ; Locomotor activity ; Hole-board ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present experiments, the effects of a wide range of doses of d-amphetamine and apomorphine were studied on investigatory behavior in an automated eight-hole box. Amphetamine (0.125, 0.25, 0.5, 1.0, 3.0, 5.0 mg/kg) increased frequency and total duration of responses, and decreased mean duration in a dose-dependent manner. The strategy and organization of responses, as measured by the order of hole-visits and hole-switching, were unchanged at lower doses of amphetamine but were altered at higher doses. Perseverative hole-poking was observed at the highest dose (5.0) as indicated by increased number of hole-pokes per hole-visit. Apomorphine (0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 mg/kg) decreased mean duration of responses, but in contrast to amphetamine markedly diminished frequency. Locomotor activity was also measured at all doses of both drugs. Our observations indicate that these two stimulant drugs both of which increase motor activity, have markedly different effects on investigatory responses. It is likely that amphetamine increases prepotent response tendencies (i.e., hole-poking), although this does not necessarily reflect enhanced exploration. Further, the results obtained with amphetamine support predictions made by the Lyon-Robbins behavioral theory of amphetamine effects.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Rat ; Operant behavior ; Fixed-interval ; Ventral tegmental area ; Neurotensin ; Substance P ; Neurokinin-α (substance K) ; d-Ala-Met-enkephalin ; Dopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neuropeptides neurotensin, substance P, neurokinin-α (substance K), and met-enkephalin are present endogenously in the ventral tegmental area (VTA), site of the A10 dopaminergic (DA) cell bodies. In the present study these four peptides were injected bilaterally into the VTA in the rat, and the effects on operant behavior were assessed. Cannulae aimed at the VTA were implanted in four groups of animals, which had been trained to bar-press for food reward on a fixed-interval, 40-s schedule. A fifth group, in which the effects of systemically administered amphetamine were assessed, was also tested. Response rate across the interval was measured, and the index of quarter-life was taken as an indication of the temporal pattern of resonding. In addition, a rate-dependency analysis was carried out for all data. Neurotensin (NT, 0.0175, 0.175, 0.5 μg in 1 μl) dose-dependently decreased response rates without affecting quarter-life, and reduced the number of reinforcements obtained. Substance P (SP, 0.1, 1.0, 3.0 μg) did not affect responding, and neurokinin-α (NKA, 0.1, 1.0, 3.0 μg) induced a small increase in responding. Quarter-life was not affected by SP or NKA, but responding on the nonreinforced lever was significantly increased by both peptides. d-Ala-met-enkephalin (DALA, 0.01, 0.1, 1.0 μg) induced a dose-dependent increase in responding which was also rate-dependent, and reduced quarter-life. DALA effects were similar to the classic pattern of responding observed after systemic amphetamine. These results suggest that although all these peptides elicit behavioral activation and may affect DA neuronal activity, the behavioral responses can be differentiated with respect to operant behavior.
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