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1

Some technical issues of vagal nerve stimulation. The approach with use of model of hippocampal theta rhythm

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Bocian R., Klos-Wojtczak P., Broncel A., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2017
|
tom 77
|
nr Suppl.1
2

Intraseptal procaine injection abolishes theta rhythm induced by vagal nerve stimulation

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Broncel A., Bocian R., Klos-Wojtczak P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2017
|
tom 77
|
nr Suppl.1
INTRODUCTION: Vagal nerve stimulation (VNS) is currently approved for treatment of both pharmacologically resistant seizures and severe refractory depression. In addition, VNS is used for treatment of Alzheimer disease, schizophrenia and central inflammation. Interestingly, VNS has also been demonstrated to enhance HPC-induced long-term potentiation (LTP) and improve memory in rats and humans. The above mentioned findings suggest the direct involvement of hippocampal formation (HPC) theta rhythm. AIM(S): We have just recently documented for the first time the presence of HPC type II theta in response to the application of VNS. VNS-induced theta rhythm appeared in different experimental protocols and, depending on the current intensity, could occur directly during VNS (brief effect) or after vagal stimulation (delayed effect). The aim of the present study was to demonstrate that the effect of left VNS on HPC theta rhythm is mediated by medial septum. METHOD(S): Anesthetized rats were implanted with vagal cuff electrodes and unilaterally with HPC recording tungsten electrode. The VNS (8 mA, 500 us, 10 s) were applied three times: before HPC injection of procaine (control), 10 min after and 60 min after. The EEG signals were analyzed off‑line using the Spike‑2 software computing system (Cambridge Electronic Design, Cambridge, UK). RESULTS: We demonstrated that medial-septal procaine injection reversibly abolished HPC type II theta rhythm induced by VNS in anesthetized rats. CONCLUSIONS: We believe that the present findings concerning type II theta rhythm open a new perspective into the study of vagal nerve involvement in central processes of sensory-motor integration, cognition and memory.
3

The effect of transcutaneous stimulation of the vagus nerve on hippocampal formation theta rhythm in anaesthetized rats

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Konopacki J., Broncel A., Bocian R., Klos-Wojtczak P.
Acta Neurobiologiae Experimentalis
|
2019
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tom 79
|
nr Suppl.1
INTRODUCTION: A number of invasive and noninvasive brain‑stimulation techniques are used in clinical neurology. Stimulation of peripheral nerves may affect brain activity through a bottom-up mechanism, for instance, by stimulating cranial nerve nuclei in the brainstem. With specific regard to peripheral methods, studies using vagal nerve stimulation (VNS) have demonstrated that neurostimulation modalities can produce robust therapeutic effects without incurring unsafe consequences on brain function. Just recently, we have demonstrated that direct VNS induced hippocampal (HPC) theta rhythms. The fact that HPC theta rhythm is directly involved in memory processing suggests that VNS can be considered as a useful treatment of patients with Alzheimer’s disease. METHOD(S): Transcutaneous stimulation of the vagus nerve (t-VNS) was performed on the level of external ear in anesthetized rats. Two uninsulated tungsten electrodes (0.1‑0.2 kΩ) were used for bipolar VNS through the left lobule of the auricle. Three different points localized on the left lobule of the auricle were tested. The following VNS intensities were applied: 0.2‑10 mA. The frequency of VNS was in range (5‑60 Hz), pulse duration (1 ms) and train duration (10 s). RESULTS: Three separate points of localized on the left lobule of the auricle responded with different HPC field responses. The most effective in inducing HPC theta rhythm was the area of entrance of the external auditory canal. CONCLUSIONS: The data obtained in the project indicated that the entrance of external auditory canal was found to be the most effective in inducing theta rhythm during t‑VNS. Further, the effectiveness of t‑VNS on HPC theta rhythm is determined by its intensity and local density of vagal endings. FINANCIAL SUPPORT: These studies were supported by The National Centre of Research and Development (grant no 01.02.00‑00‑0023/17‑001).
4

Modulation of hippocampal theta activity by transcutaneous stimulation of trigeminal nerve in anesthetized rats

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Bocian R., Broncel A., Klos-Wojtczak P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2019
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tom 79
|
nr Suppl.1
Neuromodulation is a therapeutic technique that involves modification of neural function via external stimulation, usually in the form of electrical impulses. Prominent examples of neuromodulative therapies include vagus nerve stimulation for epilepsy, Alzheimer’s disease, and even deep brain stimulation for Parkinson’s disease. Trigeminal nerve stimulation (TNS) has also been applied as a therapeutic tool in a variety of disease processes and has shown efficacy in the treatment of epilepsy and depression. AIM(S): The aim of the present study was to evaluate if transcutaneous TNS (t-TNS) could affect the hippocampal EEG activity. METHOD(S): Male Wistar rats were implanted with a tungsten microelectrode for recording hippocampal formation (HPC) field activity. Furthermore, two uninsulated tungsten electrodes were used for t-TNS in eye‑ear line in anesthetized rats. The stimulation was conducted at three point: closer to the eye (point 1), in the middle of line eye-ear (point 2), and closer to the ear (point 3). The following t‑TNS intensities ware tested: 4, 6, 8, and 10 mA. The remaining parameters of stimulation were constant: pulse duration (1 ms), train duration (10 s), frequency (10 Hz). RESULTS: Stimulation only in the point closer to the ear and in the eye-ear line was found to be productive in inducing nicely developed and well-synchronized hippocampal theta rhythm. However, t‑TNS in the range below 6 mA was found to be subthreshold (theta rhythm was not observed in HPC). Theta activity was observed at point 3 during stimulation only when the intensity of stimulation was equal or higher than 6 mA. CONCLUSIONS: Only the point located closer to the ear in the eye-ear line was found to be effective in inducing t‑TNS theta rhythm. The effectiveness of t‑TNS on hippocampal theta rhythm was determined by its intensity and density of trigeminal nerve endings. FINANCIAL SUPPORT: These studies were supported by The National Centre of Research and Development (grant no. 01.02.00‑00‑0023/17‑001).
5

Hippocampal theta rhythm as a bio-indicator of the efficiency of vagal nerve stimulation

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Klos-Wojtczak P., Broncel A., Bocian R., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2018
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tom 78
|
nr Suppl.1
Vagal nerve stimulation (VNS) refers to any tech‑ nique that stimulates the vagal nerve, including man‑ ual or electrical stimulation. Approved by the FDA at the end of the 20th century, VNS was initially used as an add-on treatment for medically refractory epilep‑ sy. Today, VNS has also been studied as a treatment for mood and cognitive disorders, such as major depression, bipolar disorder, and Alzheimer’s disease. Although VNS requires an invasive surgical procedure, this technique is increasingly widespread in medical practice. Recent‑ ly, we have demonstrated that hippocampal (HPC) thetarhythm can be produced, depending on current inten‑ sity, directly during vagal nerve stimulation (VNS) or post-stimulation. This suggests that theta EEG pattern can be used as a bio-indicator of the efficiency of VNS. In the present study, we focused on three specific tech‑ nical issues related to the stimulation procedure of the vagal nerve: 1) Does the type of electrode used for VNS and the technique of its implantation affect the param‑ eters of the HPC theta rhythm? 2) Does the type of elec‑ trode used determine the current intensity threshold of VNS-induced HPC theta? 3) Is the repeatability of the VNS effect determined by the type of electrode used? In rats (male Wistar) with an implanted tungsten micro‑ electrode (0.1–0.9 MΩ) for recording the HPC field ac‑ tivity, VNS was applied using two types of stimulating electrodes: tungsten bipolar fork electrode and plati‑ num-iridium cuff electrode. The first type of stimulating electrode touched a vagal nerve surface only during the stimulation and the second type surrounded the nerve and has contact with it throughout the entire experi‑ ment. During experiments the following VNS intensi‑ ties were tested: 1, 2, 4, 6, 8, and 10 mA. The remaining parameters were constant: pulse duration (1 ms), train duration (10 s), and frequency (10 Hz). A direct (brief) effect of VNS on the HPC field potential was evaluated. We demonstrated that using the cuff electrode for VNS offers a lower current intensity threshold for inducing HPC theta than using a fork electrode. Furthermore, in contrast to a fork electrode, the cuff electrode offers re‑ peatability of the VNS effect on HPC theta activity. The final effect of VNS is determined by many factors in‑ cluding the stimulation protocol and type of stimulating electrode used. This work was supported by RPO grant (RPLD.01.02.02-10-0067/17-00)
6

Medial-septal cholinergic mediation of hippocampal theta rhythm induced by vagal stimulation in rats

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Klos-Wojtczak P., Broncel A., Bocian R., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2017
|
tom 77
|
nr Suppl.1
INTRODUCTION: Hippocampal (HPC) theta rhythm may be important for various phenomena, including attention and acquisition of sensory information. Two types of HPC theta (types I and II) exist based on pharmacological, behavioral, and electrophysiological properties. Both types occur in conscious animals, whereas only type II (atropine-sensitive) theta is present under anaesthesia. The circuit of HPC theta synchronization includes the medial septum-diagonal band of Broca (MSDB), with cholinergic and GABA-ergic neurons comprising the two main projections from MSDB to HPC. Just recently we have demonstrated that vagal nerve stimulation (VNS) induces HPC type II theta in urethanized rats. AIM(S): The primary aim of the present study was to assess the effects of cholinergic MSDB inhibition on VNS induced HPC theta rhythm. METHOD(S): Anesthetized rats were implanted with vagal bipolar cuff electrode. VNS parameters were constant: pulse duration (1.0 ms), train duration (10 s), frequency (10 Hz) and pulse intensity 8 mA. Monopolar tungsten electrodes were implanted into HPC in accordance to standard stereotactic technique. HPC field potential was analyzed of off‑line using the Spike‑2 software computing system (CED, Cambridge, UK). In a separate experiments cholinergic, surface only during stimulation. VNS intensity was tested in a range: 0.2–10.0 mA. Remaining parameters were constant: pulse duration (1.0 ms), train duration (10 s), frequency (10 Hz). RESULTS: We demonstrated that the chronically implanted vagal cuff electrode decreased (vs tungsten electrode) the amplitude of HPC type II theta in 30%. The effect of different types of electrodes used for VNS was also noticed in the evaluation of HPC theta threshold. CONCLUSIONS: The type of the stimulation electrode (cuff vs. tungsten) used determines the final effect of VNS on hippocampal field potential.
7

Local theta rhythm mapping studies of posterior hypothalamus in vitro

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Caban B., Klos-Wojtczak P., Kowalczyk T., Bocian R., Kuzmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2014
|
tom 74
|
nr 3
Theta rhythm is one of the finest examples of synchrony in the mammalian brain. Hippocampal formation (HPC) theta is best described in rats and this EEG pattern consists of very regular, almost sinusoidal waves in the frequency range of 3–12 Hz. It is well-known that HPC theta rhythm is a result of the ascending brainstem-hippocampal synchronizing pathway activation, which originates in the pons and then projects to posterior hypothalamus, medial septum, and finally to the HPC. Recently, we have shown that administration of cholinergic agent – carbachol (75 μM), induces theta rhythm in in vitro maintained posterior hypothalamic area (PHa), specifically supramammillary nucleus (SuM) and posterior hypothalamic nuclei (PH). The purpose of this mapping study was to present the topography of areas capable of generation local theta rhythm in PHa slices as a result of carbachol administration. Supported by NCN grant 2011/01/B/N24/00373.
8

Is orexin A involved in generation of the hippocampal theta rhythm? In vivo approaches

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Klos-Wojtczak P., Caban B., Bocian R., Kowalczyk T., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2014
|
tom 74
|
nr 3
Orexins are mainly synthesized in lateral hypothalamus but orexinergic projections are present in many brain areas including cerebral cortex, thalamus, brain stem and the hippocampal formation (HPC). The study was designed to check wheather intrahippocampal injections of orexin A and blockers of orexin receptors exert effect on theta. The studies were performed on anasthetized rats. Initially spontaneous theta rhythm recorded from HPC was blocked by the intravenous injections of atropine. When the HPC theta disappered, animals were subjected local injections of orexin A and the mixture of: orexin A and SB, orexin A and TCS and orexin A with both blockers in separate studies. Theta activty was only observed in the first and second case but with a lower parameters in comparison to theta recorded after orexin A injection. Obtained results indicates crucial role of orexinergic receptors underlying theta HPC rhythm production.
9

Are GAP junctions or mineralocorticoid receptors involved in generation of posterior hypothalamic theta in rat ?

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Bocian R., Kowalczyk T., Caban B., Kazmierska P., Klos-Wojtczak P., Konopacki J.
Acta Neurobiologiae Experimentalis
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2013
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tom 73
|
nr Suppl.1
There is a large body of research indicating that occurrence of hippocampal (HPC) theta dependent on the integrity of ascending pathway originating in the brainstem reticular formation. Anatomical studies indicate that reticular influences are relayed via the posterior hypothalamus, specifically the posterior hypothalamic (PH) and supramammillary (SuM) nuclei. In addition, neurons localized in these nuclei discharge rhythmically and in phase with HPC theta. Recently we have shown that local theta activity could be generated in anesthetized rats in PH and SuM nuclei. Recorded signal was produced independently of simultaneously occurring HPC theta and had a cholinergic profile. In the preset study we extended pharmacological observation; specifically, carbenoxolone (CBX – 75 μg/ μl; gap junction (GJ) blocker and mineralocorticoid receptor agonists) was administrated into posterior hypothalamus in urethanized rats. Injection of CBX, induced well synchronized theta activity. The effect of CBX was not antagonized by injection of GJ opener – trimethylamine (45 μg/μl) – but was abolished by antagonist of mineralocorticoid receptor, spironolactone (10 μg/1 μl). These results demonstrate for the first time that PH theta is mediated not by GJ but by mineralocorticoid receptors. Studies supported by NCN grant no. 2011/01/B/NZ4/00373.
10

Posterior hypothalamic theta rhythm and local cell discharges in adult anesthetized rats

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Bocian R., Klos-Wojtczak P., Caban B., Kowalczyk T., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2015
|
tom 75
|
nr Supl.
BACKGROUND AND AIMS: Theta rhythm is the best synchronized electroencephalographic activity that can be recorded in several brain regions, for example, in the cingulate cortex, entorhinal cortex, and hippocampal formation (HPC) that is considered to be the main structure involved in the generation of theta. Just recently Kowalczyk et al. (2014) have indicated that this pattern EEG could also be observed in the posterior hypothalamic area (HPa) in anesthetized rats. Specifically, in the supramammillary (SuM) and posterior hypothalamic (PH) nuclei theta field activity was produced independently of simultaneously occurring hippocampal theta. Previous experiments have demonstrated that the HPC theta field activity is accompanied by a characteristic pattern of local cell discharges. PHa cells discharges were classified in accordance to earlier developed classification as theta-related and theta-nonrelated. Theta-related cells were classified as theta-on and theta-off. Both theta-on and theta-off cells were subclassified as phasic and tonic. The aim of the present studies was to describe firing cell repertoire during cholinergically induced theta rhythm in the PHa of rats. METHODS: All the experiments were performed in urethanized adult male Wistar rats. PHa theta rhythm and single cell activity were recorded with use of tungsten and glass microelectrodes respectively. RESULTS: One hundred fifty five out of 236 recorded in PHa cells were identified as theta non-related cells and 82 as theta-related cells: 48 theta-on, 29 theta-off, and 4 theta gating cells (the cells which activity is correlated with appearance of theta episodes). CONCLUSION: The obtained data clearly demonstrates that cholinergically induced theta activity in PHa, similarly to the HPC theta, is accompanied by local cell discharges which can be successfully classified in accordance with earlier developed criteria for HPC theta. The study was supported by National Science Centre (NCN, 2013/11/B/NZ4/04872).
11

Timing cells and carbachol induced theta rhythm in posteriol hypothalamic slice preparations of adult rats

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Bocian R., Caban B., Kowalczyk T., Klos-Wojtczak P., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2015
|
tom 75
|
nr Supl.
BACKGROUND AND AIMS: Just recently we discovered a local theta rhythm in the posterior hypothalamic area (PHa) in in vitro and in vivo conditions. Theta rhythm which appeared in the PHa was produced independently of simultaneously occurring hippocampal formation theta. In the present study we analyse the correlation of local PHa cells discharges with carbachol induced theta field potentials. Specifically, we emphasise a novel type of theta related cells which we labelled “timing cells”. METHODS: Ninety experiments were conducted on the Wistar rat’s PHa slice preparation. The local theta field potential was induced with 75 μM carbachol. Glassrecording electrodes were positioned with use of micropositioner in different regions of PHa (mainly supramammillary nuclei). Single cell activity and local field potentials were recorded simultaneously with the same electrode with respect to the ground. RESULTS: Sixty nonrelated and more that 50 theta-related cells were recorded.  Twelve of theta-related cells were recognized and labelled as “timing cells”. These cells discharge rhythmically in the frequency range of 5–8 Hz and can be phase locked with local field potentials which appeared in 1–3 s lasting theta epochs. CONCLUSION: Posterior hypothalamic theta “timing cells” are probably involved in mechanisms responsible for programing the frequency of local theta field potentials and hippocampal formation theta rhythm.
12

Theta oscillations in the posterior hypothalamic area-in vivo approach

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Bocian R., Klos-Wojtczak P., Kowalczyk T., Caban B., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2014
|
tom 74
|
nr 3
Numerous studies showed that occurrence of hippocampal theta rhythm is critically dependent on the integrity of a number structures localized at the level of brainstem and diencephalon. In detailed electrophysiological studies, conducted on anesthetized rats, we demonstrated that the posterior hypothalamic area (PHa), is not only a modulator of hippocampal formation theta but also could generate theta activity independently. The most effective areas in generation of examined EEG pattern were the supramammillary and posterior hypothalamic nuclei. Pharmacological manipulation reviled that PHa theta activity had a cholinergic (muscarinic) profile. Local injection of orexin A and B never induced theta activity in PHa. Finally, we showed that mineralocorticoid receptor but not gap junction play crucial role in generation of the posterior hypothalamic theta rhythm. Studies supported by NCN grant no. 2011/01/B/NZ4/00373.
13

Theta rhythm and local cell discharges recorded in posterior hypothalamic slices of the adult rat

76%
Caban B., Klos-Wojtczak P., Kowalczyk T., Bocian R., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2015
|
tom 75
|
nr Supl.
BACKGROUND AND AIMS: Hippocampal formation (HPC) theta rhythm is one of the best examples of neural synchrony in mammalian brain. HPC theta field potentials in rats consists of high-amplitude, almost sinusoidal waves in 3–13 Hz frequency range. It is wellknown that the pathway of theta generation originates in the nucleus reticularis pontis oralis (RPO), then RPO projects to supramammillary nuclei (SuM), and finally through the medial septal area (MS) to HPC and other limbic structures. This tract is called the ascending brainstem-hippocampal synchronizing pathway. In vivo, HPC theta frequency is modulated at least partially by SuM which consists of neurons firing in the frequency of HPC theta. However, in our previous studies we have discovered for the first time that local theta activity can also be recorded in deafferented posterior hypothalamic preparations. The present in vitro study investigates theta-related neurons and their relation to local hypothalamic theta rhythm. METHODS: 56 in vitro electrophysiology experiments were performed using brain slices taken from 56 Wistar rats. Each slice was perfused with 75 µM carbachol (cholinergic agonist) to induce rhythmic activity. The relation of firing neurons to local field theta rhythm was investigated according to an earlier developed classification. RESULTS: This study resulted in recording 21 theta-related neurons and 35 neurons classified as non-related to theta. CONCLUSION: Neuronal activity recorded in the posterior hypothalamic area in vitro resembles well-documented patterns of thetarelated cell discharges in the hippocampal formation in vitro and in vivo. Supported by NCN grant 2013/11/B/NZ4/04873.
14

Theta oscillations in the posterior hypothalamic area-in vitro approach

76%
Kowalczyk T., Caban B., Bocian R., Klos-Wojtczak P., Kazmierska P., Konopacki J.
Acta Neurobiologiae Experimentalis
|
2014
|
tom 74
|
nr 3
Hippocampal formation (HPC) theta rhythm is the largest rhythmical waveform generated by the mammalian brain. Studies performed in rodents revealed that the ascending brainstem-hippocampal synchronizing pathway originates in the nucleus reticularis pontis oralis (RPO), next RPO fibres ascend to posterior hypothalamic area (PHa) and then PHa neurons project to medial septum, known as a hippocampal theta “pacemaker”. Posterior hypothalamic area forms a critical part of that pathway, serving as a modulator of theta rhythm recorded in the HPC. However, two years ago we have discovered that the PHa is also capable of independent generation of local theta. The first aim of the present work was to review the data concerning local theta rhythm in the posterior hypothalamic area in vitro. The second aim was to perform the comparison between basic features of theta activity observed in the PHa and hippocampal formation in in vitro conditions. Supported by NCN grant 2011/01/B/N24/00373.
15

Postnatal development of theta-related cell activity in posterior hypothalamic slices

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Konopacki J., Caban B., Kazmierska P., Bocian R., Klos-Wojtczak P., Staszelis A., Kowalczyk T.
Acta Neurobiologiae Experimentalis
|
2017
|
tom 77
|
nr Suppl.1
INTRODUCTION: Hippocampal formation (HPC) theta rhythm is one of the best examples of neural synchrony in the mammalian brain. It is well-known that the pathway of theta generation originates in the pons, from where it projects to the posterior hypothalamic nuclei, and finally through the medial septal area reaches the HPC. Recent evidence shows that well-synchronized theta rhythm can also successfully be recorded locally from the posterior hypothalamic area (PHa) maintained in vivo and in vitro, specifically from the supramammillary nucleus (SuM) and the primary posterior hypothalamic nuclei (PH). Furthermore, the neuronal activity of the PH and SuM nuclei can be characterized according to the universal classification of theta-related cells which was earlier created for the hippocampus. AIM(S): The purpose of the present study is to investigate theta-related cell activity in posterior hypothalamic slices taken from adolescent rats in order to examine the age at which theta rhythm and accompanying theta-related neuronal activity appears in rats’ PHa. METHOD(S): Forty‑five experiments have been carried out using brain slices taken from 55 Wistar rats aged: 8–10 (A); 13–15 (B); 18–19 (C) and 22–24 (D) days. Each brain slice was perfused with 75 µM carbachol (cholinergic agonist) to induce theta rhythm and accompanying theta-related cell activity in the SuM and PH nuclei. RESULTS: This study resulted in recording 16 theta-related neurons, 56 timing neurons, and 103 neurons classified as non‑related to PHa theta among three experimental groups (B–D). There was no significant theta oscillations and accompanying cell discharges in slices taken from 8–10 days old rats. CONCLUSIONS: Theta oscillations as well as theta-related neuronal activity can be observed in PHa slices delivered from rats not younger than 13–15 days. FINANCIAL SUPPORT: Supported by NCN grant 2013/11/B/NZ4/04872.
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