Intraventricular injections of 6-hydroxydopamine (6-OHDA) to newborn rats resulted in a nearly complete disappearance of catecholamines in brain regions containing nerve terminals. In the hypothalamus, however, dopamine was only decreased to 60% of control levels. The exploratory (rearing and crossing) and some of the automatic type behavioral activities (grooming, chewing and gnawing), the duration of neocortical synchronization and hippocampal theta frequency were measured during light and dark periods in adulthood. Decreased exploratory and increased automatic behavioral activities were found in both light and dark periods and a high incidence of synchronization and a lowered hippocampal theta frequency in the light phase when the animals were repeatedly subjected to a strange environment. The light-dark rhythmicity of exploratory and hippocampal activity remained intact in the 6-OHDA treated rats. Furthermore, the diurnal periodicity of general motor activity was also normal. It was concluded that contrary to the active involvement of prepontine catecholamine structures in the behavioral and electrocortical responses in a novel situation, their role in controlling the light-dark rhythmical processes may not be essential.

Animals↗

PubMedDate not supplied

Beneficial effect of chronic nimodipine treatment on behavioral dysfunctions of aged rats exposed to perinatal ethanol treatment.

The long-term effects of prenatal and early postnatal ethanol exposure were assessed in adult (5-month), aged (24-month), and senescent (30-month) rats on non-aggressive intermale social behavior, and on black-white discrimination and spatial learning behaviors. Furthermore, the effects of chronic application of the Ca(2+) channel blocker nimodipine, which reportedly improves behavioral function in aging, were studied on the ethanol-induced behavioral deficits during aging. The results showed that the perinatal alcohol treatment suppressed social behavior by reducing the frequency and duration of social interactions at all ages. Black-white discrimination behavior and appetitively motivated learning in a hole-board were also markedly disturbed. Several measures of social and spatial learning behaviors of ethanol-exposed rats revealed progressive functional decline with aging. Chronic oral treatment with nimodipine improved the social activity and normalized the cognitive behavioral capabilities of aged and senescent rats exposed to ethanol. We concluded that: (1) the behavioral disabilities caused by perinatal ethanol toxicity are persistent in the rat lifespan and become more pronounced with aging; and (2) administration of nimodipine in the aging period improves, with a long-lasting efficacy, the ethanol-induced behavioral dysfunctions in aged rats.

Journal Article↗

PubMedDate not supplied

Effect of low amphetamine doses on cardiac responses to emotional stress in aged rats.

In young Wistar rats conditioned emotional stress can be characterized by a learned bradycardiac response to an inescapable footshock. In aged rats this bradycardiac response is attenuated and accompanied by suppressed behavioral arousal in response to novelty. In the present study, cardiac responses to emotional stress and behavioral reactivity to a novel experience in an open field were tested in aged and young rats under the influence of a low dose of d-amphetamine (AMPH, 0.5 mg/kg IP). AMPH administration in 27-month-old rats reinstated the bradycardiac response to emotional stress, while it failed to influence the resting heart rate in the home cage. Age-associated differences in open-field ambulation, present in drug-free conditions, were antagonized by low doses of AMPH (0.25-1.0 mg/kg). It is concluded that enhanced arousal by aminergic stimulation with AMPH in the aged rat invoked cardiac and behavioral response patterns resembling those at younger ages.

Aging↗