Biomedical subjects

J Gaito

Publications and source records attributed to J Gaito.

13 recordsLinked to original sources

PubMed1984

Suppression of kindling behavior.

Kindling behavior culminating with clonic convulsions is produced by 60-Hz sine-wave stimulation of the amygdala. This behavior can be suppressed by stimulation of the same site with 1-Hz or 3-Hz sine waves. Such results have been obtained consistently over many experiments with the manipulation of a number of variables. Suppression appears to be a transient process in that rats will return approximately to their prestimulation thresholds following 2 weeks or more of rest. The severity of suppression is greatest with 120 s or more of sine-wave stimulation and when the intertrial interval is 1 or 3 hours. The effect decreases at 24 hours; at 72 hours, 5 days, and 14 days, it appears to be minimal or nonexistent. These results suggest that tissue damage is not the basis for suppression. Further evidence for this interpretation is provided by results indicating that suppression of kindled behavior is complete and permanent with a single trial of DC stimulation (which produces tissue damage), in contrast to 1-Hz stimulated rats, which show a slow, gradual increase in threshold values over many trials and a strong recovery from the suppression later on.

Amygdala↗

PubMed1981

The effect of several intertrial intervals on the 1 Hz interference effect.

Experiments were conducted to evaluate the effect of two intertrial intervals of 1-Hz brain stimulation on kindling behavior induced by 60Hz sine wave stimulation. In two experiments, the effective threshold intensity (ETI) to elicit a convulsion was determined on four separate occasions with 5 days of daily trials between determinations. On each day experimental rats were stimulated with 1-Hz current on the first and third trials for 120 seconds duration and with 60-Hz current for 30 seconds on the second trial (1-60-1 group). A second group was stimulated with 60-Hz-current on each trial (60-60-60 group). A third group received no stimulation on Trials 1 and 3 and 60-Hz current on Trial 2 (X-60-X group). In Experiment 1, the intertrial interval was 3 hours; a 24 hour interval was used in Experiment 2. The results were similar in both experiments. For the 1-60-1 group, there was a steady increase in the intensity required to elicit a convulsion shown with 60-Hz current from EtI1 to ETI4. However, the 24 hour interval produced a lesser effect than did 3 hour interval (or the 1 hour interval used in previous experiments). Rats in the other groups maintained relatively stable values from ETI1 to ETI1, with a slight decline occurring. Suppression of convulsive behaviour on daily trials was present with the 1-60-1 groups, and nonexistent with the other groups.

Animals↗

PubMed1981

The effect of low frequency and direct current stimulation on the kindling phenomenon in rats.

An experiment was conducted to evaluate the effect of 1-Hz or direct current brain stimulation on kindling behavior induced by 60-Hz sine wave stimulation. The effective threshold intensity to elicit a convulsion was determined on four separate occasions with 5 days of daily trials between determinations. On each day one group of experimental rats was stimulated with 1-Hz sine wave current before and after stimulation with 60-Hz sine wave current (1-60-1 group). Another group received direct current stimulation and 60-Hz current (D-60-D group). A third group received only 60-Hz stimulation. Suppression of kindling behaviour usually induced by the 60-Hz stimulation occurred with 1-Hz stimulation; the mean threshold value increased on each successive determination. Suppression was most pronounced for the direct current group; it appeared after a single trial and persisted for 32 days after the last threshold determination. In contrast, most of the rats in the 1-60-1 group had recovered from the suppression after the 32 day period of nonstimulation. A second phase of the experiment indicated that the increase in threshold values for the D-60-D group occurred after a single DC stimulation. These results are consistent with the hypothesis generated by previous research that suppression following 1-Hz stimulation is not due to tissue damage.

Animals↗

PubMed1980

Gradient of interference by various frequencies on 60 Hz kindling behavior.

An experiment was conducted to evaluate the effect of various frequencies of brain stimulation on kindling behavior induced by 60-Hz sine wave stimulation. The effective threshold intensity (ETI) to elicit a convulsion was determined on four separate occasions with 5 days of daily trials between determinations. On each day experimental rats were stimulated with current of a specific frequency on the first and third trials for 60 seconds duration and with 60-Hz current for 30 seconds on the second trial (one hour intertrial interval). There were five experimental groups, one each for 1, 5, 10, 30, and 60-Hz stimulation. A sixth group received no stimulation on trials 1 and 3 and 60-Hz current on trial 2. Suppressor of convulsive behavior induced by the 60-Hz stimulation trial was present for all ETI determinations with 1-Hz and 5-Hz stimulation; the mean ETI increased on each successive determination. Suppression was prominent also for the 10-Hz group until the ETI4 determination. Suppression was moderate for the 30-Hz and 60-Hz groups. Overall, it appeared that the interference effect gradually increased with remoteness from the 60-Hz point.

Amygdala↗

PubMed1980

Interference effect of 3 Hz brain stimulation on kindling behavior induced by 60 Hz stimulation.

Experiments were conducted to evaluate the effect of 3 Hz brain stimulation on kindling behavior induced by 60 Hz sine waves stimulation. In Experiment 1, 12 rats were subjected to 40 or 60 convulsion trials with 60 Hz stimulation and then given 36 trials of 3 Hz stimulation. When these rats were stimulated again with 60 Hz sine wave current at the same brain site, none of the rats showed a convulsion in nine test trials. The intensity of stimulation had to be increased on test trial 10 to elicit convulsions for each rat. Of 10 rats in two control groups, only 1 did not convulse during the nine test trials. In Experiment 2 the effective threshold intensity (ETI) to elicit a convulsion was determined on five separate occasions with 10 days of daily trials between determinations. On each day experimental rats were stimulated with 3 Hz current on the first and third trials and with 60 Hz current on the second trial (3-60-3 group). A steady increase in the intensity required to elicit a convulsion with 60 Hz current from ETI1 to ETI5 resulted. Rats stimulated only with 60 Hz sine waves on the second trial each day (X-60-X grou,) maintained relatively stable values from ETI1 to ETI5. In the four, 10-day blocks of trials, convulsions were suppressed in 20% to 80% of the trials over the 10 day period for the 3-60-3 group, with the greatest effect occurring after about 4 days of stimulation. This suppressive effect was prominent both with rats that were at the convulsion stage prior to the first application of 3 Hz stimulation and with rats that were at preconvulsion stages. In Experiment 3 the permanency of the suppressive effect was evaluated. Eight suppressed rats from the experimental group in Experiment 2 and 4 control rats were stimulated for 90 trials over 30 days with 60 Hz current, and ETI values were determined after each set of six trials. Four of the 8 experimental rats were convulsing at ETI1 within 20 days.

Amygdala↗

PubMed1980

The effect of variable duration one hertz interference on kindling.

Experiments were conducted to evaluate the effect of various durations of 1-Hz brain stimulation on kindling behaviour induced by 60-Hz sine wave stimulation. In two experiments the effective threshold intensity (ETI) to elicit a convulsion was determined on four separate occasions with 5 days of daily trials interspersed between determinations. On each day experimental rats were stimulated with 1-Hz current on the first and third trials for 5, 15, 30, 60, 120, 180, or 600 seconds duration and with 60-Hz current for 30 seconds on the second trial. A steady increase in the intensity required to elicit a convulsion with 60-Hz current from ETI2 to ETI4 resulted for all rats with durations of 15 seconds or greater. Rats stimulated only with 60-Hz sine waves, and those in the 5 second group, maintained relatively stable values from ETI1 to ET4, with a slight decline occurring. Suppression of convulsive behavior on daily trials was modest in the 15 second group, pronounced with the 30 second group, and drastic with the other groups. The 600 second group had the greatest suppressive effect operating. The suppression effect did not appear to be due to tissue damage inasmuch as most of the experimental rats (except the 600 seconds one) convulsed again at previous low ETI levels following a 15 or 16 day rest at the end of the experiment. This result suggests that the suppression effect is a relatively transient event.

Amygdala↗

PubMed1978

Long term induction of kindled seizures in rats: interhemispheric factors.

Previous research indicated that sequential alternation of stimulation of certain homologous brain areas via chronically implanted electrodes resulted in oscillation of high and low latencies for convulsions. This phenomenon suggested the establishement of interhemispheric facilitatory-inhibitory effects as a result of repeated stimulation of the two brain sites. In the present study, the latency oscillation pattern was observed in split-brain rats as well as in bilaterally stimulated controls, but not in rats stimulated on one side only. Significant differences were observed between split-brain and control rats in terms of initial kindling rates, duration of convulsions and type of oscillation. Results are discussed in the context of possible interhemispheric mechanisms involved in long term kindling.

Amygdala↗

PubMed1976