Jolanta Orzeł-Gryglewska

Publications of Jolanta Orzeł-Gryglewska

• Induction of hippocampal theta rhythm by electrical stimulation of the ventral tegmental area and its loss after septum inactivation.

  Authors: Jolanta Orzeł-Gryglewska, Magda Kuśmierczak, Irena Majkutewicz, Edyta Jurkowlaniec

  Brain research. 02/2012; 1436:51-67.

  The ventral tegmental area (VTA), which may be one of the structures involved in regulation of hippocampal theta rhythm, sends direct projections to the hippocampus and also to the forebrain septum,The ventral tegmental area (VTA), which may be one of the structures involved in regulation of hippocampal theta rhythm, sends direct projections to the hippocampus and also to the forebrain septum, the key centres involved in theta generation. In the present study we aimed at assessing which projections from the VTA (direct or through the septum) participate in regulation of hippocampal electric activity. Experiments were conducted on 3 groups of urethanised male Wistar rats. In the first group (n=6) electrical stimulation of the VTA was used to evoke theta rhythm episodes in hippocampus. Stimulation was repeatedly applied in control conditions and after procainic blockade of the septum. The second group (n=6), subjected to unilateral electrical stimulation of the VTA (30-s stimulation at 10-min intervals during 2h) and to subsequent detection of Fos expression, served to measure neuronal activation of the target mesolimbic structures. Activation levels of selected structures were compared to data from analogous stimulation of the zona incerta (ZI, the third group, n=6). Stimulation of the VTA immediately generated regular theta rhythm in both hippocampi. Inactivation of the septum with procaine temporarily abolished this effect. VTA stimulation increased the density of Fos in the ipsilateral nucleus accumbens. Stimulation of the ZI never generated theta but evoked significant induction of Fos expression in the hippocampus. Our data suggest that the projection through which the VTA enhances theta rhythm is not direct but is incorporated into the main route of theta generation, which involves septum as the main relay node.

• Involvement of GABAergic transmission in the midbrain ventral tegmental area in the regulation of hippocampal theta rhythm.

  Authors: Jolanta Orzeł-Gryglewska, Magda Kuśmierczak, Edyta Jurkowlaniec

  Brain research bulletin. 11/2010; 83(6):310-20.

  Previously we indicated that the ventral tegmental area (VTA) may belong to the system regulating hippocampal theta rhythm. In the present study, we aimed at assessing the role of the GABAergicPreviously we indicated that the ventral tegmental area (VTA) may belong to the system regulating hippocampal theta rhythm. In the present study, we aimed at assessing the role of the GABAergic system of the VTA in regulation of hippocampal electric activity. Male Wistar rats received unilateral intra-VTA microinjection of either bicuculline (50ng/0.5μl, n=9), muscimol (100ng/0.5μl, n=10) or phaclofen (500ng/0.5μl, n=9). 1-min tail pinch stimulations were applied at 10-min intervals to evoke theta rhythm episodes in hippocampus. We analysed peak power (P(max)) and corresponding frequency (F(max)) of EEG signal at delta and theta bands. Bicuculline induced theta rhythm in both hippocampi with 0 latency, continuous for ca. 33min. Phaclofen also induced theta but in this group it appeared with latency (17.45±3.16min on average), lasted for ca. 33.6min and during this time was interrupted by periods of irregular activity of variable length. Tail pinch was not applied in these groups. Muscimol induced an opposite effect: depression of theta P(max) with simultaneous increase in delta P(max) and a decrease in F(max) delta during episodes of tail pinch-evoked theta. This effect had variable latency and no return to the control EEG could be observed. We propose that GABA activity in the VTA is of tonic character, so that abolition of this mechanism produces immediate effect, i.e. theta induction (strong by GABA(A) and weak by GABA(B) receptors blockade), whereas enhancing the already present GABAergic inhibition causes delayed, prolonged changes expressed as gradual loss of theta synchronisation.

• Hippocampal theta rhythm after serotonergic activation of the pedunculopontine tegmental nucleus in anesthetized rats.

  Authors: Paweł Matulewicz, Jolanta Orzeł-Gryglewska, Mark J Hunt, Weronika Trojniar, Edyta Jurkowlaniec

  Brain research bulletin. 10/2010; 83(5):257-61.

  The pedunculopontine tegmental nucleus (PPN), as a part of reticular formation activating system, is thought to be involved in the sleep/wake cycle regulation, and plays an important role in theThe pedunculopontine tegmental nucleus (PPN), as a part of reticular formation activating system, is thought to be involved in the sleep/wake cycle regulation, and plays an important role in the generation and regulation of hippocampal rhythmical slow activity. The activity of PPN can be modulated by serotonergic system, mainly through multiple projections from raphe nuclei, which can influence PPN neurons through different classes of 5-HT receptors. In the present study, the effect of intra-PPN injection of two serotonin agonists: 8-OH-DPAT and 5-CT, on hippocampal formation EEG activity was examined in urethane-anesthetized rats. The study found that the microinjections induced prolonged spontaneous theta rhythm in both hippocampi with a short latency. The results obtained suggest that local inhibition of presumably cholinergic neurons in the PPN acts as a trigger for hippocampal theta activity.

• Consequences of sleep deprivation.

  Authors: Jolanta Orzeł-Gryglewska

  International journal of occupational medicine and environmental health. 01/2010; 23(1):95-114.

  This paper presents the history of research and the results of recent studies on the effects of sleep deprivation in animals and humans. Humans can bear several days of continuous sleeplessness,This paper presents the history of research and the results of recent studies on the effects of sleep deprivation in animals and humans. Humans can bear several days of continuous sleeplessness, experiencing deterioration in wellbeing and effectiveness; however, also a shorter reduction in the sleep time may lead to deteriorated functioning. Sleeplessness accounts for impaired perception, difficulties in keeping concentration, vision disturbances, slower reactions, as well as the appearance of microepisodes of sleep during wakefulness which lead to lower capabilities and efficiency of task performance and to increased number of errors. Sleep deprivation results in poor memorizing, schematic thinking, which yields wrong decisions, and emotional disturbances such as deteriorated interpersonal responses and increased aggressiveness. The symptoms are accompanied by brain tissue hypometabolism, particularly in the thalamus, prefrontal, frontal and occipital cortex and motor speech centres. Sleep deficiency intensifies muscle tonus and coexisting tremor, speech performance becomes monotonous and unclear, and sensitivity to pain is higher. Sleeplessness also relates to the changes in the immune response and the pattern of hormonal secretion, of the growth hormone in particular. The risk of obesity, diabetes and cardiovascular disease increases. The impairment of performance which is caused by 20-25 hours of sleeplessness is comparable to that after ethanol intoxication at the level of 0.10% blood alcohol concentration. The consequences of chronic sleep reduction or a shallow sleep repeated for several days tend to accumulate and resemble the effects of acute sleep deprivation lasting several dozen hours. At work, such effects hinder proper performance of many essential tasks and in extreme situations (machine operation or vehicle driving), sleep loss may be hazardous to the worker and his/her environment.

• Microinjection of procaine and electrolytic lesion in the ventral tegmental area suppresses hippocampal theta rhythm in urethane-anesthetized rats.

  Authors: Jolanta Orzeł-Gryglewska, Edyta Jurkowlaniec, Weronika Trojniar

  Brain research bulletin. 02/2006; 68(5):295-309.

  The midbrain ventral tegmental area (VTA), a key structure of the mesocorticolimbic system is anatomically connected with the hippocampal formation. In addition mesocortical dopamine was found toThe midbrain ventral tegmental area (VTA), a key structure of the mesocorticolimbic system is anatomically connected with the hippocampal formation. In addition mesocortical dopamine was found to influence hippocampus-related memory and hippocampal synaptic plasticity, both being linked to the theta rhythm. Therefore, the aim of the present study was to evaluate the possible role of the VTA in the regulation of the hippocampal theta activity. The study was performed on urethane-anesthetized male Wistar rats in which theta rhythm was evoked by tail pinch. It was found that unilateral, temporal inactivation of the VTA by means of direct procaine injection resulted in bilateral suppression of the hippocampal theta which manifested as a loss of synchronization of hippocampal EEG and respective reduction of the power and also the frequency of the 3-6 Hz theta band. Depression of the power of the 3-6 Hz component of the EEG signal was also seen in spontaneous hippocampal EEG after procaine. The permanent destruction of the VTA by means of unilateral electrocoagulation evoked a long-lasting, mainly ipsilateral depression of the power of the theta with some influence on its frequency. Simultaneously, there was a substantial increase of the power in higher frequency bands indicating decrease of a synchrony of the hippocampal EEG activity. On the basis of these results indicating impairment of synchronization of the hippocampal activity the VTA may be considered as another part of the brainstem theta synchroning system.

• Involvement of GABAergic transmission in the midbrain ventral tegmental area in the regulation of hippocampal theta rhythm

  Authors: Jolanta Orzeł-Gryglewska, Magda Kuśmierczak, Edyta Jurkowlaniec

  Brain Research Bulletin.

  Previously we indicated that the ventral tegmental area (VTA) may belong to the system regulating hippocampal theta rhythm. In the present study, we aimed at assessing the role of the GABAergicPreviously we indicated that the ventral tegmental area (VTA) may belong to the system regulating hippocampal theta rhythm. In the present study, we aimed at assessing the role of the GABAergic system of the VTA in regulation of hippocampal electric activity. Male Wistar rats received unilateral intra-VTA microinjection of either bicuculline (50 ng/0.5 μl, n = 9), muscimol (100 ng/0.5 μl, n = 10) or phaclofen (500 ng/0.5 μl, n = 9). 1-min tail pinch stimulations were applied at 10-min intervals to evoke theta rhythm episodes in hippocampus. We analysed peak power (Pmax) and corresponding frequency (Fmax) of EEG signal at delta and theta bands. Bicuculline induced theta rhythm in both hippocampi with 0 latency, continuous for ca. 33 min. Phaclofen also induced theta but in this group it appeared with latency (17.45 ± 3.16 min on average), lasted for ca. 33.6 min and during this time was interrupted by periods of irregular activity of variable length. Tail pinch was not applied in these groups. Muscimol induced an opposite effect: depression of theta Pmax with simultaneous increase in delta Pmax and a decrease in Fmax delta during episodes of tail pinch-evoked theta. This effect had variable latency and no return to the control EEG could be observed. We propose that GABA activity in the VTA is of tonic character, so that abolition of this mechanism produces immediate effect, i.e. theta induction (strong by GABAA and weak by GABAB receptors blockade), whereas enhancing the already present GABAergic inhibition causes delayed, prolonged changes expressed as gradual loss of theta synchronisation.