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Time-dependent, learning-related changes in hippocampal excitability were evaluated by recording from rabbit CA1 pyramidal neurons in slices prepared at various times after acquisition of trace eyeblink conditioning. Increased excitability (reduced postburst afterhyperpolarizations and reduced spike-frequency adaptation) was seen as early as 1 hr after(More)
1. The excitability of CA3 pyramidal neurons was assessed with intracellular recordings in hippocampal slices from behaviorally naive rabbits. CA3 pyramidal neurons had large (-13.1 +/- 0.3 mV; mean +/- SE) postburst afterhyperpolarization (AHPs) and exhibited robust spike-frequency adaptation (accommodation) to prolonged (800-ms) depolarizing current(More)
Hippocampally-dependent trace eyeblink conditioning has been shown to be affected by aging. Aging animals take more trials to acquire the association and are more likely to be unable to learn the task. Hippocampal neurons show decreased post-burst afterhyperpolarizations (AHPs) and less accomodation after conditioning, in a time-dependent fashion which may(More)
1. Cellular properties were studied before and after bath application of the dihydropyridine L-type calcium channel antagonist nimodipine in aging and young rabbit hippocampal CA1 pyramidal cells in vitro. Various concentrations of nimodipine, ranging from 10 nM to 10 microM, were tested to investigate age- and concentration-dependent effects on cellular(More)
Rabbits 2 to 41 months of age were conditioned in the 500 ms trace eyeblink paradigm to cross-sectionally define the age of onset and the severity of age-associated impairments in acquisition of this relatively difficult hippocampally dependent task. Using a strict behavioral criterion of 80% conditioned responses (CRs), age-associated learning impairments(More)
Cellular properties of CA1 neurons were studied in hippocampal slices 24 hr after acquisition of trace eyeblink conditioning in young adult and aging rabbits. Aging rabbits required significantly more trials than young rabbits to reach a behavioral criterion of 60% conditioned responses in an 80 trial session. Intracellular recordings revealed that CA1(More)
The role of the hippocampus (HPC) in trace eye-blink conditioning was evaluated using a 100-ms tone conditioned stimulus (CS), a 300- or 500-ms trace interval, and a 150-ms air puff unconditioned stimulus (UCS). Rabbits received complete hippocampectomy (dorsal & ventral), sham lesions, or neocortical lesions. Hippocampectomy produced differential effects(More)
Golgi-impregnated neurons from rat perirhinal cortex (PR) were classified into one of 15 distinct morphological categories (N = 6,891). The frequency of neurons in each cell class was determined as a function of the layer of PR and the age of the animal, which ranged from postnatal day 0 (P0) to young adulthood (P45). The developmental appearance of(More)
Intracellular recordings were made from rabbit hippocampal CA1 neurons in vitro using slices from aging and young adult rabbits. Calcium action potentials were studied in the presence of 4 microns tetrodotoxin using electrodes filled with 2M CsCl. Increasing concentrations of the dihydropyridine L-type calcium channel antagonist nimodipine were tested on(More)
CA1 field potentials evoked by Schaffer collateral stimulation of hippocampal slices from trace-conditioned rabbits were compared with those from naive and pseudo-conditioned controls. Conditioned rabbits received 80 trace conditioning trials daily until reaching a criterion of 80% conditioned responses in a session. Hippocampal slices were prepared 1 or 24(More)