Effects of extracts of different parts of the brain of kindled animals on seizure activity of recipient rats

The peptide-containing fraction was emitted from the hippocampal and ventral mesencephalic region tissue of rats kindled with subconvulsant doses of corazol. Extracts were prepared by the help of hot acetic acid on the stage of generalized clonic-tonic seizure development. The intraventricular injection of VMR-extracts in relatively high dose increased seizure reactions which were induced in intact recipient rats by intraperitoneal corazol injection. The intraventricular injection of the extract in relatively low dose (100 times less) suppressed corazol-induced seizures in recipients. Data are discussed from the point of view of pathological epileptic system formation and the role played by peptides in supporting it's activity during pharmacological kindling.     

Changes in the functional parameters of the brain structures under the influence of enkephalin-like tetrapeptidamide

In complex neurophysiological and cytobiochemical study single injections of tetrapeptide amide (TPA) caused a short-term analgetic effect which manifested itself in the absence of motor reactions and EEG changes of cortical and subcortical brain structures after painful stimulation of extremities. This effect was accompanied by changes of some indices of transmitter (monoamine oxidase) and protein metabolism in the cerebral hemispheres at cellular and subcellular levels. In 30-40 min after a TPA injection, EEG suppression and absence of EPs to light flashes were observed in cortical and subcortical structures. Simultaneously motor disorders developed. The observed EEG changes had an undulatory character: on the second day EEGs were restored and on the third day--suppressed once again. This period of TPA action was accompanied by varied changes of the investigated types of metabolism. The question of the necessity of systemic approach to the study of TPA action is discussed, as such an approach allows to reveal complex neurophysiological and fine biochemical relations in the reactions of brain structures and in animal behaviour.     

Effect of short-term adaptation to hypoxia on the development of acute cerebral circulatory disorders in rats genetically disposed to epilepsy

The exposure of KM rats genetically predisposed to autogenic convulsive fits, to hypobaric hypoxia had a protective effect on the extension of cerebrovascular disorders in conditions of acoustic stress, reducing the severity of motor disorders and the degree of intracranial hemorrhage (subdural, subarachnoidal, intraventricular).     

The role of muscarinic cholinoreceptors in the retrieval of the instrumental food conditioned reflex in cats

It was demonstrated in cat experiments that impairment of the retrieval of appetitive instrumental conditioning observed after systemic administration of antagonists of muscarinic central cholinoreceptors scopolamine (a nonselective M1 antagonist) and trihexyphenidyl (relatively selective M1 antagonist) could be connected with central and peripheral side effects of these antagonists. It was established that in case of the absence of side effects (low doses of trihexyphenidyl, 1 mg/kg) the blockade of M1-cholinoreceptors led either to selective fall-off of the motor instrumental reaction with in the presence of contextual behavior and other conditioned reactions or the appearance of errors that seemingly was indicative of the disturbance of triggering and realization of the motor program as the most important component of conditioning performance. The systemic injection of trihexyphenidyl (10 mg/kg), scopolamine (0.03 and 0.06 mg/kg) and nonselective peripheral antagonist methylscopolamine (0.03 mg/kg) led to changes in the general functional state (disorders in the emotional and motivational sphere), the expression of which depended on the individual sensitivity to anticholinergic drugs. The disturbance of CR retrieval observed in parallel with side reactions was characterized by a complete cessation of conditioning and apparently was not associated with memory deterioration.     

Sodium deficiency enhances the behavioral responses to centrally administered vasopressin in rats

The ability of sodium deficiency to stimulate vasopressin (VP) release was examined by determining if sodium deficiency sensitizes the animal to the behavioral disruption caused by intraventricular injections of VP. In sodium-replete rats, intraventricular injections of 50 ng VP on Day 1 had no effect on behavior, but this dose elicited abnormal behaviors (barrel rolls, hind-limb extensions) when administered on Day 2, indicating a sensitization phenomenon. In separate experiments, the first intraventricular injection of 50 ng VP in sodium-deficient but not in sodium-replete rats also elicited barrel rotations followed by hind-limb extension. Intraventricular injection of VP also disrupted motor behavior in sodium-replete rats that had multiple prior experiences with sodium deficiency but not in naive rats. These results show that sodium deficiency can mimic the effect of central injections of VP in sensitizing the brain to the behavioral effects of exogenous VP. This suggests that sodium deficiency induces the central release of VP.     

Anticonvulsant properties of the cerebrospinal fluid during activation of the antiepileptic system of the brain

Cerebrospinal fluid (CSF) was obtained after 30-40 sessions of daily electrical stimulation of the cat cerebellum vermis. The intraventricular injection of CSF (10 microliters) to Wistar rats increased the latent period of initial seizure manifestations, significantly reduced the number of animals with seizures and reduced the severity of seizures induced by korazol injection (40 mg/kg). Analogous seizure changes were observed in rats after intraventricular injection of CSF (10 microliters) from cats subject to 3-10 electroshock seizure fits. Intraventricular injection of CSF (250 microliters) obtained from cats after electroshock to cats with strychnine-induced epileptic foci in the brain cortex led to the suppression of the epileptic activity. The conclusion was made that different ways of antiepileptic system activation cause the accumulation of endogenous antiepileptic substances in CSF.     

Effect of pGlu-Tyr-Arg-Trp-NH2 on the serum level of gonadotropins in the male rat]

The tetrapeptide synthesized by Folkers et al. was injected intraperitonealy in normal adult male rats. The release of FSH is significant 90 and 120 minutes after injections of 150, 100, 250 microgram of this substance. An increase of LH was only observed at 120 minutes after injection of 100 microgram of the tetrapeptide. Thus, in rats dissociation between FSH and LH release can be observed.     

Development of passivity in the rat: effect of tranquilizers and antidepressants

Following the views on passivity as one of the features of depression-like behaviour in rats developing as a result of unavoidable painful stimulation an attempt was made to eliminate by antidepressant drugs the passivity manifested in an almost complete absence of motor searching reactions in an "open field" and a maze. However tranquilizing drugs rather than antidepressants to a greater extent induced the effect presupposed. Hence the type of passivity under study corresponds more likely to neurotized behaviour than to a special depression-like. In the second series of experiments the action was studied of multiple injections of antidepressants on similar manifestations of passivity as well as on alimentary instrumental conditioned responses in rats with initially expressed passive character of behaviour. In this case too neither the presupposed increase of motor searching reaction was observed nor any significant changes in the rate of instrumental conditioning nor elimination of its failures of a "refuse" type.     

Morphine-like activity of the enkephalin analog Tyr-D-Ala-Gly-Phe-NH2

The analgetic activity of the tetrapeptide enkephalin analog, its influence on the interneuronal transmission of excitation in various areas of the central nervous system and on opiate receptors of vas deferens were studied. The tetrapeptide was found to have a marked analgetic effect during intravenous injection to mice but to be less active than morphine. The tetrapeptide as well as morphine inhibited the impulse summation in rabbits and both spontaneous and bradykinin-induced neuronal activity in the rat sensory motor cortex. The tetrapeptide inhibited the contractions of isolated vas deferens in mice. The opiate antagonist naloxone eliminated both analgetic effect of the tetrapeptide and its inhibitory effect on the impulse summation, neuronal activity and contractions of vas deferens.     

The effect of acute ethanol administration on the neuronal activity of the motor cortex of the rabbit in its food-acquisition behavior]

Units activity of anterolateral area of rabbits motor cortex, realizing instrumental food-acquisition behaviour was studied at acute injection of ethanol and in control experiments (injection of physiological solution) in order to compare possible ethanol effects on the motor area of the cortex with effects revealed by us earlier at studying the activity of the limbic cortex units in the same experimental conditions. It was shown that after ethanol injection the number of active units and the pattern of the motor cortex units specialization in contrast to the limbic one remained constant. Nevertheless, composition of the motor cortex units involved in subserving the behaviour changed because of recruitment [correction of recrutation] of one cells (from V-VI layers of the cortex) in this process and exclusion of other ones (from II-IV layers). The value of activation frequency ratio to the frequency of the background of the involved units increased.     

A comparative analysis of the morphochemical changes in the neurons of the visual and sensorimotor cortices and the nucleus accumbens of rats administered tuftsin

White rats were treated with a single administration of tetrapeptide tuftsin (Thr-Lys-Pro-Arg) in the dose 300 mcg/kg (b.w). Using interferometry, the protein content and concentration were assessed 15, 30 and 60 minutes after injection. The area of the neuron cytoplasm and nucleus were measured too. The nucleoplasmic balance and dispersion were calculated. Significant alterations in the protein contents and cellular area, nucleoplasmic balance and dispersion were detected in neurons of visual, sensomotor cortex and of n. accumbens. A possible interrelation is discussed between tuftsin action and the functional activity of neurons, between the level of their protein metabolism and establishment of emotional and motor response.     

Vitamins E and C prevent the impairment of retention of an inhibitory avoidance task caused by arginine administration

S-adenosylmethionine (SAMe) is present in all tissues and functions as the sole donor of methyl groups in over 100 different methylation reactions. Recent reports suggest that direct intraventricular injection of SAMe induces Parkinsonian like symptoms in rats including seizures, tremors, hyperkinesia and abnormal posture. In order to assess the influence of SAMe on rat behavior we have undertaken a study to examine the effect of 3 different forms of SAMe. Guide cannulae were sterotaxically implanted into the lateral ventricle of male SD rats ( n = 5 for each group) using either ketamine or chloral hydrate anesthesia. 48 h post surgery the rats received a 5-μL injection containing 1 μmol of either SAMe-toluenedisulfonate, SAMe-butanedisulfonate, SAMe-chloride, or vehicle (butanedisulfonate, toluenedisulfonate or saline). Locomotor activity was monitored using the TruScan monitoring system and by videotape recording for 1 h. The videotape was reviewed by one of the authors (RD-A) who is experienced with animal models of epilepsy. SAMe injected animals had frequent myoclonic and tonic seizures, and occasional generalized clonic seizures. SAMe induced behavioral seizures and tremors occurred only in rats that had previously been anesthetized with chloral hydrate, and not in rats that received ketamine. The number of movements recorded during the 1-h period were significantly increased in SAMe injected animals compared to control groups in both chloral hydrate and ketamine anethetized rats. Our studies indicate that there is an anesthetic dependency for SAMe induced seizures and tremors.     

Inhibitory effects of substance P on the gamma-amino-butyric acid and gamma-hydroxybutyric acid-induced growth hormone and prolactin release in male rats

Gamma-aminobutyric acid (GABA) at 50 μg/10 μ1 was injected into the lateral ventricle after pretreatment with intraventricular injection of 1 μg of substance P in urethane anesthetized male rats. Thirty minutes after GABA injection the animals were decapitated and blood samples were collected from the trunk. Serum GH and prolactin were determined by radioimmunoassays. The intraventricular GABA elicited a significant increase in both serum GH and prolactin levels. Intraventricular substance P itself had no effect on serum GH and prolactin, but it inhibited the GABA-induced increases in serum GH and prolactin. Gamma-hydroxybutyric acid (GHB) was intraperitoneally injected with and without an intraventricular injection of substance P in urethane anesthetized rats. The GHB injection significantly increased serum GH and prolactin levels. Pretreatment with substance P completely inhibited the GHB-induced GH and prolactin responses. These results suggest that substance P might interact with GABA in the central nervous system.     

Analgesic and Antipyretic Activities of a Novel Tetrapeptide in Rats

The efficacy of a novel tetrapeptide sequence, FLPS (Phe-Leu-Pro-Ser), to alleviate severe pain associated with surgical incision is demonstrated in the Brennan model, a model used for developing new drugs for postoperative pain in humans. The tetrapeptide (100 mg/kg dose) administered by subdermal injection completely alleviated post-incisional pain in rats using the hindpaw withdrawal as an endpoint response. When the tetrapeptide (0.15 mg/paw) was topically applied to the vicinity of the surgical wound, it also alleviated pain. Statistically significant increases in pain threshold (assessed by von Frey filaments pressed against the surgical wound, 15–20 min after dosing) were observed on the day of surgery and on the third day post-surgery. Up to a 0.5°C decrease in body temperature under basal conditions and yeast-provoked pyrexia was observed at doses that alleviate pain. The tetrapeptide does not exhibit any significant anti-edema activity in carrageenan-induced hindpaw edema, and does not affect human recombinant cyclooxygenase-2 activity, indicating that the analgesic property of the tetrapeptide is unlikely to be mediated through inflammatory pathways. The tetrapeptide at 10 μM, a dose that is sufficient to increase the pain threshold in rats, does not compete with naloxone for the opioid receptors in membrane preparations from rat brain, indicating that it does not mediate its effect through the opioid receptors. It also does not bind to the vanilloid receptor, indicating that peripheral vanilloid receptors are not involved in pain relief by the tetrapeptide.     

Conditioned posture changes in dogs after systemic administration of dopaminergic agents

Influence of systemic injection of some dopaminergic drugs on conditioned postural rearrangement prior to instrumental movement realization and on other motor components of instrumental reaction as well as on the performance of the instrumental task itself--was studied in chronic experiments in 5 dogs on a model of instrumental defensive reflexes connected with maintenance of a certain posture. Drugs were used influencing the nigrostriate dopaminergic system, i.e. dopamine agonist L-DOPA and haloperidol blocking dopamine striate receptors. All the motor components of the instrumental reaction and first of all conditioned postural rearrangement were modified by systemic haloperidol injection. Initial components of the postural rearrangement were modified to the greatest extent, in particular the period of preparation of the animal to the posture change increased. On the contrary, the latency of initiation of postural rearrangement was sharply shortened by systemic injection of L-DOPA. On the other hand, the main component of the postural change, i.e. redistribution of body mass among the bearing limbs (the values of which significantly increased after preliminary stimulation of the head of the caudate nucleus) changed insignificantly during modulation of the striatum dopamine level.     

Instrumental heterogeneous responses to 2 successive complex stimuli with a common initial stimulus in the dog

Formation and achievement of heterogenous instrumental reflexes to two consecutive complex stimuli was studied in dogs. Under the action of conditioned complex stimulus tone--Pause--tone, the dogs may be trained not to have a motor response to the first tone presentation, but perform alimentary instrumental reaction only to its repeated administration. Introducing into the experiment not only alimentary but also defensive complex stimulus stone-pause--light resulted in a change in animal's reactions in such a sequence: at first alimentary instrumental reaction was disinhibited under the action of the preparatory stimulus and during the pause, then bieffector responses appeared, further on in most of the dogs motor defensive reactions mainly took place. Trigger stimuli evoked the adequate instrumental reaction.     

Central origin on the excito-motric action of morphine on intestine]

In ewew fitted with a cerebro-ventricular cannula and equipped with extra-cellular bipolar electrodes on the antrum and proximal small intestine, an intraventricular injection of morphine at a dose (40 micrograms/kg) ineffective peripherally was followed within 1 min by an increased spike activity of the duodenum without disruption of the occurrence of migrating myoelectric complexes. This effect was paralleled by a reduction of antral motility and abolished by small intraventricular doses of nalorphine. After an intravenous injection of large doses of the drug drug (0.8 mg/kg), spike activity was increased at both jejunal and duodenal level without changes in the antrum and followed by a long-lasting disorganization of the motor profile. The results suggested a centrally mediated gastro-duodenal effect of morphine.     

Poster Sessions AP10: Learning,Memory and Behavior. S‐adenosylmethionine induced seizures are anesthetic dependant

S‐adenosylmethionine (SAMe) is present in all tissues and functions as the sole donor of methyl groups in over 100 different methylation reactions. Recent reports suggest that direct intraventricular injection of SAMe induces Parkinsonian like symptoms in rats including seizures, tremors, hyperkinesia and abnormal posture. In order to assess the influence of SAMe on rat behavior we have undertaken a study to examine the effect of 3 different forms of SAMe. Guide cannulae were sterotaxically implanted into the lateral ventricle of male SD rats (n = 5 for each group) using either ketamine or chloral hydrate anesthesia. 48 h post surgery the rats received a 5‐μL injection containing 1 μmol of either SAMe‐toluenedisulfonate, SAMe‐butanedisulfonate, SAMe‐chloride, or vehicle (butanedisulfonate, toluenedisulfonate or saline). Locomotor activity was monitored using the TruScan monitoring system and by videotape recording for 1 h. The videotape was reviewed by one of the authors (RD‐A) who is experienced with animal models of epilepsy. SAMe injected animals had frequent myoclonic and tonic seizures, and occasional generalized clonic seizures. SAMe induced behavioral seizures and tremors occurred only in rats that had previously been anesthetized with chloral hydrate, and not in rats that received ketamine. The number of movements recorded during the 1‐h period were significantly increased in SAMe injected animals compared to control groups in both chloral hydrate and ketamine anethetized rats. Our studies indicate that there is an anesthetic dependency for SAMe induced seizures and tremors.     

The dependence of hippocampal electrical activity on the probability of the reinforcement of a conditioned food stimulus

In three dogs the dynamics was studied of changes in the number of instrumental motor reactions, the heart rate and the hippocampus theta rhythm was studied at the change of constant reinforcement to various regimes of probable reinforcement of alimentary conditioned stimulus. At 70 and 50% levels of the reinforcement the instrumental reflex appeared in response to all presentations of the signal stimulus. The greatest decrease in the number of reactions took place at 5% probability. The heart rate both in the intersignal period and at getting of empty feeder depended on the used probability of reinforcement and individual characteristics of animals. The frequency of the theta rhythm in all dogs was the highest at the 30% level and the lowest values were found at the 5% level of reinforcement. The obtained facts testify once more to complex genesis of emotional excitation, the value of which depends both on informational (uncertainty) and motivational (significance of reinforcement) factors.     

Effect of ACTH and its fragment on brain catecholamines in intact and adrenalectomized rats.

Brain catecholamine metabolism was monitored by distribution of labelled noradrenaline (3H-NA) after intraventricular injection to intact and adrenalectomized rats. The adrenalectomy produced an increased disappearance rate of the labelled pool in the hypothalamus, hippocampus and neocortex. These changes could be prevented by hydrocortisone pretreatment. Painful stimuli resulted in an increased disappearance of the labelled pool in both intact and adrenalectomized rats. The implantation of hydrocortisone into the tuberoinfundibular region prevented the stress-induced changes of the catecholamine metabolism. Intraventricular administration of ACTH1-24 and ACTH4-10 produced a significant increase of the disappearance rate in different brain regions of adrenalectomized rats. The blocking of catecholamine synthesis by intraventricular injection of alpha-methyl-m-tyrosine resulted in a marked decrease of the labelled pool but did not prevent the ACTH-induced decrease of the tracer pool. On the other hand, the blocking of monoamine-oxydase activity by Pargyline led to a marked increase of the labelled pool but intraventricular administration of ACTH led to an increase of the disappearance rate. The mechanism of ACTH action on brain catecholamine metabolism is still obscure, however, an increased release of the NA to ACTH peptides is very likely in the light of the present observations.