Asuman Gölgeli

Effects of age and anxiety on learning and memory.

This study aims to investigate the effects of age and anxiety on behavior, learning and memory in rats. Before and after the anxiety and learning tests, locomotor activity, exploratory activity and autonomic functions of the rats were tested in open field area. At the beginning and at the end of behavior tests, urines were collected so as to determine 5-hydroxyindolaceticacid (5-HIAA) levels. Following these tests, rats were anesthetized and their serum corticosteron (CORT) levels were analyzed. After anxiety, except for defecation, all parameters in open field such as line crossing, rearing, sitting and number of grooming were decreased in both young and aged animals. 5-Hydroxyindolaceticacid levels were decreased and serum CORT levels were increased, it is supported that especially the aged rats were much more affected from anxiety compared to the young ones. Elevated T-maze results show that emotional learning did not change while conditioned performance was tested in the closed arm and unconditioned performance was tested in the open arm. Nevertheless, it is observed that aging leaded to extensions in avoidance responses and thus caused difficulty in learning. In water maze test, rats showed higher performance in reaching the platform in repetitive trials; this demonstrates that they have learned by environmental cues. Experimental group had not better performance in reaching the platform according to control group, so this supports that anxiety affects spatial learning. As a conclusion, it could be stated that especially in aged rats, anxiety that is created by elevated T-maze and cat odor and supported with 5-hydroxyindoleacetic acid and serum corticosterone, causes difficulty in emotional and spatial learning.

The effects of pentylenetetrazole-induced status epilepticus on behavior, emotional memory, and learning in rats

Status epilepticus (SE) can cause spatial learning, memory, and behavioral deficits; however, little information is available, especially regarding the effects of such seizures on emotional memory and learning functions. We investigated the effects of SE on emotional memory, learning, and behavior in mature rats over short and long periods. SE was induced in 50- to 60-day-old rats (P50-P60) using intraperitoneal injections of pentylenetetrazole (PTZ, n = 20); control rats received saline (n = 10). All animals were tested with elevated T-maze and open-field tests on the 1st, 7th, 14th, and 180th days after SE to evaluate emotional memory, learning, and behavior. The number of fecal boli increased, and one-way escape latency was long in a short period after SE. PTZ-induced SE causes transient memory deficits, which is related to unconditioned fear, but it did not cause any persistent abnormalities of behavior, emotional memory, and learning in mature rats.

Effects of cigarette smoking on cognitive processing

Several previous studies have reported that cigarette smoking enhances performance of cognitive processing. These enhancements are generally attributed to the pharmacological effects of nicotine, while there is some debate whether the effects of smoking/nicotine are a result of recovery from abstinence. Evoked potentials (EPs) and event related potentials (ERPs) of the brain have been applied as an index of information processing in a wide variety of normal and cognitive impaired subjects. This study was carried out on 20 healthy students (23 ± 2.3 years old) from the medical faculty of City University. Study population comprised ten chronic cigarette smokers consuming an average of 14 ± 4.2 cigarettes per day, with a history of smoking for more than one year. Ten non--smokers served as control. Standard oddball paradigm was presented, and EEG activity was recorded at the Fz, Cz, Pz electrode sites. Twenty responses to target stimuli were averaged at each location. N1, P2, N2, and P300 components were evaluated in these recordings. Amplitudes were measured relative to prestimulus baseline, and peak latencies were defined as the time point of maximum amplitude. It was found that there were no significant differences between either N1, P2, N2, P300 amplitudes or peak latency values of cigarette smokers and non smokers. As a result, chronic cigarette smoking generally does not improve cognitive processing

Ketamine reduces lidocaine-induced seizures in mice.

Systemic toxic reactions to local anesthetics are brought about by absolute overdosage, and, most commonly, inadvertent intravascular injections. The anti-convulsant action of ketamine has been studied. However, the effect of ketamine on lidocaine-induced convulsions has not been reported. This study investigated the effect of ketamine on lidocaine-induced seizures in mice. Mice (32–41 g) were divided into 2 groups, 15 in each group, and were pretreated with intraperitoneal normal saline solution or intraperitenoeal (ip) ketamine before lidocaine. Group 1 (N = 15) received 75 mg kg ip lidocaine; Group 2 (N = 15) received 20 mg kg ketamin ip; 5 min later 75 mg kg lidokaine ip were applied. Clinical features, incidences, latencies, durations, and mortality rate of convulsions were recorded. After 75 mg kg lidocaine injection, ataxia, loss of righting reflex, and generalized tonic-clonic convulsions were seen within 2–5 min in Group 1. Generalized tonic-clonic convulsions were seen in 8 mice and deep sedation was seen in 7 mice in Group 2 (p < .05). Generalized status epilepticus occurred in one mouse in both groups. Three mice from Group l and one mouse from Group 2 died during convulsions. There were no differences between the two groups with regard to the onset and duration of seizures (p > .05). It was concluded that ketamine significantly prevented lidocaine-induced generalized tonic-clonic seizures; on the other hand, the lethality of lidocaine was least reduced by ketamine.

Habituation of the Auditory Evoked Potential in a Short Interstimulus Interval Paradigm

The present experiment was carried out to investigate elicitation and habituation of the auditory event related potentials with stimulus trains utilizing a short interstimulus intervals (ISI) of 1500ms. Scalp event related potentials elicited by auditory stimuli were recorded in 10 male subjects. Thirty auditory stimuli were presented binaurally over headphones to every subject with a duration of 1000ms, each with a constant ISI of 1500ms. No task relevance was given to the stimuli. Wave-forms were collected using a Pentium 100 computer.

Effects of pentylenetetrazole-induced status epilepticus on behavior, emotional memory and learning in immature rats

Status epilepticus (SE) can be harmful to the developing brain. Our knowledge of the emotional and behavioral consequences of generalized SE in developing animals remains limited. Therefore, we investigated the short- and long-term effects of pentylenetetrazole (PTZ)-induced SE on emotional memory and learning and behavioral parameters in immature rats. SE was induced in 16- to 20-day-old rats (P16-P20) using intraperitoneal injections of PTZ (n=21); control rats received saline (n=10). All animals were tested using an elevated T-maze and open-field test 2, 14, 30, and 180 days after SE, to evaluate emotional memory and learning and behavior. Anxiety levels decreased 2 and 14 days after SE, and conditioned learning of PTZ-treated immature rats was better than that of the control rats. These results indicate that a decreased anxiety level facilitates conditioned learning. Behavioral changes are transient, and no emotional memory or learning deficits occur following PTZ-induced SE in immature rats.

EFFECT OF HYPERGLYCEMIA ON ELECTRODERMAL ACTIVITY IN DIABETIC RATS

This study investigated the relationship between hyperglycemia and electrodermal activity (EDA) parameters in streptozotocin (STZ) induced diabetic rats. The article evaluates the course of development of neurophysiological alterations in the peripheral nervous system in diabetic rats through EDA. Rats were made diabetic using a moderate dose of STZ (DI) and high dose (DII). The placebo group (P) was injected with physiological saline. EDA was recorded 1 h before the injection (beginning, 0, day), 1st day (one day after the injection) and 10th day. Skin conductance level (SCL) was lower in DII than P on the 1st and the 10th days. The SCL and SC fluctuation rate (SCFr) of DI were significantly lower on the 10th day compared to their first record. SC response rate (SCRr) was lower on the 10th day compared to the 1st day, in the DI. In the DI, SCL, SC fluctuation rate (SCFr) and SC response rate (SCRr) were lower on the 10th day compared to the 1st day. The DII was statistically higher in electrodermal non-responsiveness compared to other groups on the 1st day. The results obtained show that hyperglycemia affects the peripheral nervous system, and EDA parameters are affected by blood glucose level. It is suggested that EDA is a simple and non-invasive electrophysiological method in early diagnosis of diabetic neuropathy.

SEX-RELATED DIFFERENCES IN TIME ESTIMATION AND THE ROLE OF EXPECTANCY

In this study, using auditory sequences, the authors designed an examination with three phases of stimulus-driven attention that is based on the possibility that involuntarily time shifts of attention are caused by nonunique stimulus properties. The purpose was to investigate whether attending and temporal expectancies are influenced by stimuluss properties and by sex. In each phase, an auditory stimulus train was presented, and the participant was asked to tap rhythmically in order to anticipate every fifth stimulus (or, in the third phase, the lack of it). The time between button pressing and stimulus onset was measured using a computer. Time estimation was accepted as a false response if the subject responded before 150 ms or 150 ms later from onset stimulus time. Error numbers were greater in Phase 3 and there was no significant difference between the male and female subjects for any of the phases when error numbers were compared. On the other hand, males pressed the button more accurately than females. Time estimation performance was affected by sex and expectancy-related motor responses are very important for time estimation.

EVALUATION OF AUDITORY EVOKED POTENTIALS FROM THE INFERIOR COLLICULUS IN RAT

This study aimed to investigate the usefulness of auditory evoked potentials (AEPs) in rats. To this end, N1, P2 latencies, and the N1 P2 amplitude of responses to different acoustic stimuli from rats, which were implanted with permanent electrodes in the inferior colliculus (IC), were evaluated and used to demonstrate the frequency characteristics of IC region. Permanent electrodes were implanted in IC regions of 7 male albino rats by the stereotaxic method. The animals were exposed to five tones series of stimuli (1000 Hz, 2000 Hz, 4000 Hz, 6000 Hz, and 8000 Hz tones with 1500 ms interstimulus intervals) of 70 dB with a duration of 1000 ms. AEPs)were recorded and analyzed with the Brain-Data Acquisition system. There were no statistically significant differences in N1, P2 latencies, and the N1-P2 amplitude of AEPs from IC regions of rats as a result of changes in the frequency of stimulus. It was determined that the dominant frequency activity of the IC to acoustic stimulus was theta-alpha band, with theta as the peak frequency. As a result it was concluded that there are similarities between the N1, P2 components of rat AEPs, and human AEPs. We have suggested that the rats may provide a useful model for investigating the generation of middle latency components of AEPs in humans.

Zinc-Induced Alterations in Contractile Properties of Rat Diaphragm Muscle In Vitro

The effect of zinc ions on the isometric contraction of rat diaphragm muscles in the presence and in the absence of external calcium was studied. Using a transducer, the isometric force was measured as a function of supramaximal electrical stimulation, either directly or indirectly applied to the muscle. The following parameters were measured: peak twitch tension, PT, twitch contraction time, CT, relaxation half-time, RT-1/2, and peak rates of tension increase and decrease, +dP/dt and -dP/dt. The following zinc-induced alterations were observed: an increase of the PT; a decrease of the RT-1/2; an increase in the +dP/dt and -dP/dt. The CT was not changed significantly. Our results suggest that zinc ions have a positive inotropic effect on isolated diaphragm muscle. The increase in PT may be explained by a zinc-activated Ca2+ uptake by sarcoplasmic reticulum. This was followed by an increase in the rate of rise of tension development, which was secondary to increased -dP/dt. The mechanism(s) by which extracellular Ca2+ contributes to this action of zinc is not known.