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G Brozek

Publications and source records attributed to G Brozek.

At least 19 recordsLinked to original sources
PubMed2003

Level of vigilance influences licking frequency in rats.

In rats, the basic licking rhythm is generated by the central pattern generator located in the brainstem. Nevertheless, the licking frequency can be regulated between about 7.5 and 4 Hz by changing the drinking conditions. If these conditions are kept constant, the licking frequency can be influenced only to a minor degree by factors such as deprivation level, type of solution, and phase of the session. The aim of our study was to compare the licking frequency of rats at different levels of vigilance. We investigated spontaneous licking of rats by an electrical lick sensor; parallel behavior monitoring was also performed. Animals kept in a stable environment and showing a lower level of vigilance licked at a rate of 5.96 Hz, fully vigilant rats licked significantly more rapidly at a frequency 6.57 Hz. The fastest rate of licking (6.49 Hz and 6.82 Hz, respectively) was encountered in alert rats under a mild stress caused by the presence of a second animal in the experimental box. The vigilance level is thus another factor affecting the licking rate of rats that should be taken into account in behavioral licking experiments.

Animals↗
PubMed2002

The effect of direct administration of drugs into the licking generator in rats.

Spontaneous licking of thirsty rats was investigated under the effect of GYKI (an AMPA/kainate receptor antagonist) and of 2-amino-5-phosphonopentanoic acid (AP5, an NMDA receptor antagonist) applied intracranially into the central rhythm generator of licking. Adult Long Evans male rats were stereotaxically implanted with guiding cannulae aimed at the oral part of nucleus reticularis gigantocellularis (NRG). After a recovery (1 week at least), animals after 24 h water deprivation were trained to drink in an experimental box. Then 1 microl of GYKI (1 mM solution) or 1 microl of AP5 (20 mM solution) was administrated by microinjection through the guiding cannula directly into the target structure. Lick-lick interval (LLI) was recorded by an electrical lick sensor and analysed with a laboratory computer Pentium. Localisation of the administration was checked by a routine histological method. GYKI administration significantly prolonged the LLI i.e. slowed down licking frequency. The effect was immediate and began to dwindle in the period between 10 min to 2 h. Licking frequency under the influence of AP5 was faster (shorter LLI). This effect culminated after 30 min and almost disappeared after 2 h. Both our findings are in a good accordance with those of Grillner's group that NMDA receptors are important for slow swimming movements while non-NMDA receptors are responsible for fast ones.

2-Amino-5-phosphonovalerate↗
PubMed2001

Acquisition and retrieval of conditioned taste aversion is impaired by brain damage caused by two hours of pilocarpine-induced status epilepticus.

The effect of Cavalheiro's pilocarpine model of epileptogenesis upon conditioned taste aversion (CTA), an important example of nondeclarative memory, was studied in adult Long Evans rats. Deterioration of CTA was studied during the silent period between pilocarpine-induced status epilepticus (SE) and delayed spontaneous recurrent seizures. SE was elicited by i.p. injection of pilocarpine (320 mg/kg ) and interrupted after 2 hours by clonazepame (1 mg/kg i.p.). Peripheral cholinergic symptoms were suppressed by methylscopolamine (1 mg/kg i.p.), administered together with pilocarpine. CTA was formed against the salty taste of isotonic LiCl. In the experiment of CTA acquisition, the CTA was formed and tested during the silent period after SE. In the experiment of CTA retrieval, the CTA was acquired before SE and the retrieval itself was tested during the silent period. Retrieval of CTA acquired before SE was impaired more than the retrieval of CTA formed during the silent period. Our findings indicate that epileptic seizures can disrupt even non-declarative memory but that CTA formed by the damaged brain can use its better preserved parts for memory trace formation. Ketamine (50 mg/kg i.p.) applied 2 min after the onset of pilocarpine-induced status epilepticus protected memory deterioration.

Animals↗
PubMed2000

Interstrain differences in cognitive functions in rats in relation to status epilepticus.

Cognitive functions of Long Evans (N=30) and Wistar rats (N=32) were compared using a Morris water maze. Under control conditions the Long Evans rats were more efficient in this test, their average escape latency after 5 days of training (6.4+/-0.1 s, mean+/-S.E.M.) was significantly shorter than that of the Wistar rats (11.0+/-0.1 s). When the training was completed seizures were induced by an intraperitoneal injection of pilocarpine (330 mg/kg in the Long Evans strain and 350 mg/kg in the Wistar rats) 30 min after pretreatment with N-methylscopolamine (1 mg/kg i.p.). Clonazepam (1 mg/kg i.p.) was used to interrupt clonic seizures after 2 hours of continuous activity. Approximately one quarter of rats in both strains did not develop seizures. Severe convulsive status epilepticus was common in Long Evans rats (23 out of 30). In contrast, only 12 Wistar rats generated convulsive status epilepticus and the same number of animals exhibited only bursts of motor seizures separated by periods without convulsions (temporary seizures). Mortality after pilocarpine-induced status epilepticus was considerably higher in the Long Evans rats than in the Wistar rats. After a latency of 2-3 weeks spontaneous recurrent seizures appeared in all animals surviving status. Cognitive memory was tested during the 'silent period' between status and recurrent seizures. The Long Evans rats were unable to find the platform at the 3rd and 6th day after status but then their performance rapidly improved. The performance of the Wistar rats undergoing status epilepticus was seriously deteriorated and it never normalized, whereas the animals with temporary seizures exhibited only a transitory marginal prolongation of latencies. The hippocampal formation was damaged by status epilepticus in rats of both strains - the Long Evans rats exhibited more extensive damage of subfields CA1 and CA3, whereas in the Wistar rats a complete destruction of hilar neurons was observed in addition to partial CA1 and CA3 damage.

Animals↗
PubMed2000

Functional ablation of deep cerebellar nuclei temporarily impairs learned coordination of forepaw and tongue movements.

The role of the cerebellum in complex skilled movements was assessed by the use of functional ablation technique. Rats were trained to synchronize tongue and forepaw movements in a drinking box equipped with a retractable spout which was automatically withdrawn after every lick but could be returned by pressing and releasing a lever placed 4 cm below the spout. The animals learned to perform short presses synchronized with the lick cycle in such a way as to allow continuous drinking. The contribution of the neocerebellum to these lick-associated instrumental movements was estimated by intracranial injection of 2 ng of tetrodotoxin into the dentate and lateral part of interposed nuclei. Bilateral blockade of the mainly neocerebellar output interfered with learned synchronization of licking and bar pressing, but did not suppress licking from a stationary spout and only decreased the licking frequency by 10%. It is concluded that the tongue-forepaw synchronization is disrupted by elimination of the neocerebellar output but for a much shorter time (< 9 h) than the tetrodotoxin-induced inactivation of the lateral part of the caudate nucleus (72 h) reported earlier. The results confirm participation of cerebellar hemispheres in learned tongue-forepaw synchronization, but indicate at the same time that elimination of this link can be easily compensated.

Animals↗
PubMed2000

The effect of otolith and semicircular canal convergence on the VOR during eccentric rotation.

VOR gain modulation was systematically investigated in the Rhesus monkey (M. mulatta) during centric and variable eccentric (up to 50 cm) sinusoidal rotation (4 Hz, 0.75 degree) with the nose facing in- or outward to test convergence of otolith and semicircular canal afferences. Earth-stationary lit LED-targets were placed at different distances (12-180 cm) from the monkey. Results were compared to biological demands. During centric rotation at 4 Hz when smooth pursuit mechanisms do not play a role, VOR gain--as expected--was approximately 1 without dependence on target distance. Phase of VOR and centrifuge were shifted by about 180 degrees as was predicted. If the monkey was rotated eccentrically with the nose facing outward the expected gain enhancement for close targets was obtained. Maximal experimental VOR gain during 4 Hz rotation was 4.4 which was close to demand at 50 cm eccentricity and 15 cm target distance (predicted gain: 4.6). If the nose points inward three situations have to be distinguished from simulation: (1) target behind the axis of rotation--VOR gain decrement should occur; (2) target on the axis of rotation--"inverse VOR suppression"; (3) target between monkey and axis of rotation--phase reversal. Experimentally, VOR gain decrement was obtained (situation 1). VOR gain was minimal (but not zero) for targets around the axis of rotation (situation 2). Situation 3 has not been investigated in detail so far.

Acceleration↗
PubMed2000

[Pregnancy outcome in women after ovulation induction].

UNLABELLED: The study was performed in 116 pregnant women after ovulation induction in 1995-1999. The pregnancy outcome was analysed. In 92 of 116 women (79.3%) successful outcome ("home taken baby") was observed. In 56 of them (60.9%) spontaneous delivery took place, in 4 (4.3%) women birth with vacuum extractor was performed, and in 32 (34.8%) caesarean section was done. In 24 of 116 women (20.7%) the pregnancy outcome was unsuccessful. In 12 of them (10.3%) missed abortion, and in 7 women (6%) spontaneous abortion was observed. 2 patients (1.7%) had caesarean section (in 24th and in 29th week of gestation) because of preeclampsia. One birth (0.9%) was premature because of the cervical incompetency. CONCLUSIONS: The pregnancy outcome in women after ovulation induction is frequently (20.7%) unsuccessful. The delivery in patients after ovulation induction frequently (34.8%) takes place with caesarean section.

Adult↗
PubMed1999

[Medical students movement in Stefan Batory university in Vilno between 1919-1939].

In 1938 Stefan Batory University counted 3110 students of whom 736 studied in Medical Faculty. The students were of the following nationalities: Poles - 76.6%, Jews - 13.4%, Russians - 6.8%, White Russians 3.0%, Lithuanians - 2.7%, Ukrainians - 0.9%, Germans - 0.4%, others - 0.1%. The students had 77 associations: 25 scientific (included Medicale Circle and Jewish Medical Students Association); 3 of Selfhelp (Fellowship Help and 2 Jewish selfhelp organizations); 20 of political, religious and national characters; 10 regional (eg. Lodz, Grodno, Bialystok, Inflanty, Kowno, Silesia and Zaglebie); 12 corporations; 2 sport organizations: Academic Sport Federation and Jewish Academic Sport Club; in 5 of different character was Academic Choir. Students had their own journal "Alma Mater Vilnensis".

History, 20th Century↗
PubMed1997

[Human memory and its animal models].

The term memory expresses the ability of the human or animal CNS to store information. Memory can be classified according to different principles. Short-term memory and long-term memory represent the basic classification. Within the long-term memory, a declarative and a nondeclarative form can be distinguished. The declarative memory provides a consciously accessible record of individual previous experiences. Nondeclarative memory includes motor skills, perceptual procedures and simple conditioned reactions. It is characteristic for nondeclarative knowledge, that the individual is not well aware what exactly he learned. Formation of the declarative memory traces requires processing in the hippocampus, while nondeclarative learning does not. Studies on animals suggest that declarative memory is stored by changes in synaptic strength at contacts involving NMDA receptors in the hippocampus. The ion channel associated with the NMDA receptor is usually blocked by Mg2-. It becomes unblocked only when the postsynaptic cell is depolarized, for instance during simultaneous activation of NMDA and nonNMDA receptors. Resulting Ca2+ influx into the postsynaptic cell initiates activation of second-messenger kinases followed by strengthening the synapses that were activated during depolarization. The molecular substrate of nondeclarative memory in unknown. Both forms of memory can be modelled in laboratory animals and analyzed experimentally. An analogy of declarative memory requires memory-stored cognitive maps of the outside world and lists of expected consequences of various actions. Motor learning can serve as a suitable model of complex nondeclarative (procedural) memory.

Animals↗
PubMed1996

Localization of the central rhythm generator involved in spontaneous consummatory licking in rats: functional ablation and electrical brain stimulation studies.

Localization of the central rhythm generator (CRG) of spontaneous consummatory licking was studied in freely moving rats by microinjection of tetrodotoxin (TTX) into the pontine reticular formation. Maximum suppression of spontaneous water consumption was elicited by TTX (1 ng) blockade of the oral part of the nucleus reticularis gigantocellularis (NRG), whereas TTX injections into more caudal or rostral locations caused significantly weaker disruption of drinking. To verify the assumption that TTX blocked the proper CRG of licking rather than some relay in its output, spontaneously drinking thirsty rats were intracranially stimulated via electrodes chronically implanted into the oral part of the NRG. Lick-synchronized stimulation (a 100-ms train of 0.1-ms-wide rectangular pulses at 100 Hz and 25-150 microA) applied during continuous licking (after eight regular consecutive licks) caused a phase shift of licks emitted after stimulus delivery. The results suggest that the stimulation has reset the CRG of licking without changing its frequency. The reset-inducing threshold current was lowest during the tongue retraction and highest during the tongue protrusion period of the lick cycle. It is concluded that the CRG of licking is located in the oral part of NRG.

Animals↗
PubMed1996

Auditory frequency and intensity discrimination in pigmented rats.

Auditory function was investigated in seven pigmented hooded rats (strain Long-Evans) with the aid of an operant conditioning procedure. Frequency difference limen was measured at frequencies from 0.5 to 64 kHz at 50 dB sensation level (SL). Weber ratios (frequency difference limen/frequency) in this range varied between 3.7 and 7.3%. The decline in the intensity of the stimulus from 50 to 10 dB SL was accompanied by a slight increase in the frequency difference limen. The frequency difference limen values were similar for frequency shifts upwards or downwards. Intensity discrimination was measured at 50 dB SL at frequencies of 2, 8 and 32 kHz. Intensity difference limen was frequency independent and amounted to 2.9 +/- 0.5 dB in conditions of upward intensity shift. The values of intensity difference limen measured in conditions of downward intensity shift were significantly larger and amounted to 6.5 +/- 1.6 dB. The characteristics of hearing function found in these experiments correspond with those described by other authors in albino rats and indicate that albinism in the rat has no significant influence on auditory frequency and intensity discrimination.

Acoustic Stimulation↗
PubMed1995

[Non-reflex activity of the CNS].

Recent studies of biological rhythms have modified Sherrington's concept of nervous system as exclusively reflexive to include the fact that some neural activity is also endogenously rhythmic. Reflexes are undoubtedly the most important components of animal's and human behavior. But are reflexes the basic units of all complex movements and acts? Rhythmical movements such as respiration, walking and running and other forms of locomotion, as well as rhythmical alimentary processes such as respiration, walking and running and other forms of locomotion, as well as rhythmical alimentary processes such as licking, mastication, and the peristaltic propulsion of nutrients and waste are examples of acts controlled by intrinsic oscillators, so called central pattern generators. Information from the periphery is, however, essential for controlling the extent and rate of movements. Between reflex and non-reflex activity it is possible to place complex species-specific responses called by ethologists fixed-action patterns. Recent investigators have shown that many complex sequences of behavior like speech or piano playing are determined by an internal plan, rather than being generated by a "chain" of reflexes. Non-reflexive activity appears earlier in ontogeny, and is probably phylogenetically older than reflexes.

Animals↗
PubMed1994

Differential contribution of motor cortex and caudate nucleus to instrumental tongue-forelimb synchronization in rats: a functional ablation study.

The functional ablation technique was used to assess the role of motor cortex and caudate nucleus in a complex skilled movement. Rats were trained to synchronize tongue and forepaw movements in a drinking box equipped with a retractable spout which was automatically withdrawn after every lick but could be returned by pressing and releasing a lever placed 4 cm below the spout. The animals learned to perform short presses synchronized with the lick cycle in such a way as to allow continuous drinking. Neural circuits implementing these lick-associated instrumental movements were blocked by intracranial injection of 10 ng of tetrodotoxin. Bilateral blockade of the motor cortex interfered with lick-synchronized bar pressing, but did not significantly influence licking from a stationary spout. Both licking and bar-pressing were impaired by bilateral injection of tetrodotoxin into the lateral part of the caudate nucleus for the duration of the tetrodotoxin-induced inactivation of the target region. The instrumental tongue-forelimb synchronization recovered considerably later, i.e. after two to three days. Functional blockade of the medial part of the caudate nucleus caused only a partial impairment of lick-synchronized bar pressing lasting less than 7 h and did not significantly influence consummatory licking. It is concluded that the tongue-forepaw synchronization is disrupted by blockade of motor cortex or lateral caudate considerably longer than the performance of the isolated component movements.

Animals↗
PubMed1991

Synchronisation of tongue and forepaw movements in the rat: a model of instrumental muscle synergy.

Acquisition of new skills is often implemented by the formation of coordinated movements of functionally unrelated muscles. This situation was modelled in rats trained to lick at a retractable spout which was automatically withdrawn after termination of every lick but could be returned by pressing and releasing a lever placed 4 cm below the spout. Rats (n = 12) learned to perform short presses (50 ms) synchronized with the lick cycle in a way allowing continuous drinking. When the distance of the lever from the box was increased from 5 mm to 12.5 mm or when the force required for lever operation was raised from 20 g to 90 g, the lick-press interval increased in multiples of the interlick interval. Licking ceased during the lever pressing but regular timing of subsequent licks indicated uninterrupted activity of the licking generator. It is concluded that the coordination of orofacial and forelimb muscles engaged in licking and lever pressing, respectively, is accomplished by propagation of the activity of the lick generator to cortical and subcortical motor centers.

Animals↗
PubMed1987

Systemic ketamine blocks cortical spreading depression but does not delay the onset of terminal anoxic depolarization in rats.

Ketamine (KET)-induced blockade of cortical spreading depression (CSD) was examined in rats (n = 51) anesthetized with pentobarbital (50 mg/kg). CSD was elicited by intracortical injection of 1 microliter of 0.15 mol/l potassium acetate 10-40 min after i.p. injection of 6-50 mg/kg KET. KET was almost ineffective at 6 mg/kg but prevented CSD propagation at 12 mg/kg and at higher dosages. The blockade was maximal 20 min after injection. Terminal anoxic depolarization elicited by N2 breathing developed in control rats after a latency which was not significantly different from that in rats pretreated with 50 and 100 mg/kg KET. The failure of CSD blocking dosages of KET to delay the onset of terminal anoxic depolarization indicates that excitotoxic amino acids play different roles in the mechanism of the anoxia-elicited and CSD-related autoregenerative ionic shifts.

Animals↗
PubMed1985

Substitution of natural conditioned and unconditioned stimuli by artificial stimuli does not prevent acquisition of conditioned taste aversion in rats.

Attempts to replace a natural conditioned stimulus (taste) by electrical stimulation and a natural unconditioned stimulus (gastrointestinal disorder) by intracranial application of harmaline in the conditioned taste aversion (CTA) paradigm are described. The taste is replaced either by electrical stimulation of taste receptors of the tongue or by intracranial self-stimulation of the lateral hypothalamus, both triggered by licking. Both stimuli lose their rewarding properties when paired with gastrointestinal distress whereas self-stimulation triggered by nose poking is not affected by the same procedure. The unconditioned stimulus was replaced successfully by intracerebral injection of harmaline hydrochloride. The effect of the injection of 3-6 micrograms harmaline into the region of the inferior olive is comparable to that of systemic injection of 10 mg/kg harmaline. Electrophysiological analysis of the effect of locally and systemically applied harmaline indicates that the drug probably elicits CTA by activation of bulbar structures including the lateral reticular nucleus and lateral vestibular nucleus.

Animals↗