PubMed Health⌕ Search

Biomedical subjects

M R Kruk

Publications and source records attributed to M R Kruk.

10 recordsLinked to original sources
PubMed1991

Behavioural effects of NMDA injected into the hypothalamic paraventricular nucleus of the rat.

Electrical stimulation of the hypothalamic paraventricular nucleus (PVH) and of the adjacent dorsal hypothalamic area (DHA) evokes grooming behaviour. Microinjections of low doses of kainic acid, an agonist of the kainate type of glutamate receptors, into the same area evokes the same behaviour. To test whether other glutamate receptors are involved, microinjections with N-methyl-D-aspartic acid (NMDA) were made into the PVH/DHA area and the behaviour was observed. From the total observation time (30 min) up to 73% was spent on grooming, accompanied by yawning. Pronounced feeding behaviour was also noticed at 3 injection sites but not until 23 min after injection. Conclusions are that neurones within the PVH/DHA area are involved in grooming behaviour, possibly via glutamatergic innervation. The interaction between grooming and feeding behaviour at the level of the PVH is discussed.

Animals↗
PubMed1991

Grooming induced by intrahypothalamic injection of ACTH in the rat: comparison with grooming induced by intrahypothalamic electrical stimulation and i.c.v. injection of ACTH.

Intracerebroventricular (i.c.v.) injection of adrenocorticotropic hormone (ACTH) elicits grooming in the rat, but the neural organization of this response is still obscure. Electrical stimulation (EHS) in an area around the hypothalamic paraventricular nucleus (PVH) also elicits grooming. This hypothalamic area contains many ACTH-immunoreactive fibres. Injection of ACTH1-24 (0.3 microgram/0.3 microliters) in the same area elicits intense grooming responses in the rat. Latency, intensity and precise patterning of the grooming response are dependent upon the exact site of injection. Comparison of grooming responses elicited by EHS, ACTH injected i.c.v. and ACTH injected in the PVH reveals that these are slightly dissimilar. This may provide clues as to the brain mechanisms involved in the organization of the different components of grooming. EHS does not elicits scratching and even reduces 'spontaneous' scratching. Also, EHS-elicited grooming is characterized by short pauses. The time-course of appearance of yawning differs between ACTH-PVH and ACTH-i.c.v. injections. Excited locomotion elicited only by ACTH-i.c.v. is apparently caused by ACTH-sensitive systems outside the PVH. The results suggest that the ACTH-containing part of the hypothalamus around the PVH is crucially involved in the organization of grooming behaviour. We believe that at this level in the brain, the subroutines of grooming, scratching and yawning are integrated into one skin maintenance behaviour.

Adrenocorticotropic Hormone↗
PubMed1991

Ethology and pharmacology of hypothalamic aggression in the rat.

Stimulation of a restricted area of the rat's hypothalamus elicits unprovoked violent attacks of a species-specific and strain-specific nature. Serotonergic drugs affecting 5HT1 receptors, propranolol, the 5HT re-uptake inhibitor fluvoxamine, and the anxiolytic oxazepam, inhibit hypothalamic attack selectively. However, hypothalamic attack is extremely unsensitive for many drugs that do affect attack provoked by natural stimuli. The pharmacology, the form, the impulsive nature, the absence of preliminaries, the insensitivity for contexts and ultimate aims of aggressive behaviour, suggest that a mechanism with the limited function of damaging adversaries of any kind is activated in the hypothalamus. This hypothalamic attack release mechanism (harm) requires specific sensory input for the expression of specific motor components, such as biting and kicking. The back and dorsal part of the opponent's head are the important attack releasing and directing stimuli. Attacks of this nature are part of the "aggressive" repertoire of the rat in natural settings. "Lateral" or "sideways" postures, specific for intermale fighting cannot be induced by hypothalamic stimulation. Drug, lesion, and stimulation studies suggest that attack and "sideways" postures are under the control of different central mechanisms. These results suggest new ways to describe the patterning of aggressive behaviour. There are interesting ethopharmacological similarities between hypothalamic responses and obsessive compulsive disorders (OCD) in man. It is suggested that further study of the ethopharmacology of hypothalamic responses may shed light on the pathophysiology of impulsive behavioural symptoms which in man seem to be beyond the control of appraisal or context.

Aggression↗
PubMed1989

Interactions between simultaneously activated behavioral systems in the rat.

Interactions between electrically induced attack and teeth-chattering from 1 electrode and grooming from another were examined in male albino rats. The interaction between electrically induced attack and deprivation-induced feeding, as well as the effect of food deprivation on attack, was also studied. Results indicate that attack appears to be a dominant response, for it suppressed grooming and feeding at a low level of activation. On the other hand, it was not affected by simultaneously induced grooming or feeding. However, food deprivation decreased the threshold for attack, leaving attack latency, attack form, or bite targets unaffected. Teeth-chattering, suggested to be related to attack and flight, was also a dominant response. Results suggest that interactions between behavioral systems are in favor of the systems that must act acutely on activation in order to survive. Apparently, the regulations governing these interactions are represented in the functional organization of the brain.

Aggression↗
PubMed1988

Hypothalamic substrates for brain stimulation-induced patterns of locomotion and escape jumps in the rat.

The hypothalamic response area for electrically induced locomotion was determined using moveable electrodes and discriminant analysis as an appropriate statistical technique. At 241 out of 641 stimulated sites locomotion was induced. The distribution of locomotion sites is relatively diffuse. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate or low probability of inducing the response. The response is considered to be mediated by fibres of the subpallido-pedunculopontine system, which includes the mesencephalic locomotor region. Different categories of exploratory and flight-directed locomotion were distinguished, and response areas for both categories were determined. In addition the response area for escape jumps was delimited. Exploratory locomotion is mainly induced from the lateral hypothalamus, while flight-directed locomotion and escape jumps are evoked from the medial hypothalamus. The response area for exploratory locomotion reflects the lateral hypothalamic distribution of the subpallidal projection to the mesencephalic locomotor region. A diffuse substrate for flight behavior seems to occupy almost the entire medial hypothalamus. It is concluded that a locomotor subroutine subserving different behavioural mechanisms can be activated at many hypothalamic sites.

Animals↗
PubMed1988

Hypothalamic substrates for brain stimulation-induced attack, teeth-chattering and social grooming in the rat.

In this paper the boundaries of the hypothalamic response areas for brain stimulation-induced attack, social grooming and teeth-chattering were delimited. A total of 641 hypothalamic sites in 71 male CPW/WU Wistar rats were electrically stimulated. Positive sites for any behavioural response cluster into restricted hypothalamic areas. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate and low probabilities of inducing the behavioural response concerned. Each response has its own response area where probabilities are high. Neuroanatomical correlates of these response areas are discussed. The response area of attack is suggested to be an integrative processing area, stimulation of which overrules some aspects of integration and directly activates the behavioural program of attack. Although some authors consider all three responses to be part of the behavioural repertoire of aggression, the response areas are not identical. Social grooming and attack are considered to be induced from different neural systems. Similarly, attack and teeth-chattering have been shown to derive from different neural mechanisms, despite substantial overlap of both response areas. It is suggested that teeth-chattering derives from the simultaneous activation of both attack and flight tendencies. No further distinctions with respect to threshold current intensities can be made within responses areas. However, the underlying neural substrates are not homogeneous, for thresholds vary along the course of individual electrodes.

Aggression↗
PubMed1987

Hypothalamic substrates for brain stimulation-induced grooming, digging and circling in the rat.

Despite a great number of studies concerned with the induction of specific behavioural responses from the rat hypothalamus by electrical brain stimulation, hypothalamic response areas and underlying neural substrates have never been determined accurately. In this study the boundaries of the hypothalamic response areas for grooming, digging and circling were delimited using moveable electrodes, an enriched environment containing a variety of goal objects, and an appropriate statistical technique. A total of 641 hypothalamic sites in 71 male CPB/WU Wistar rats were electrically stimulated. Results are plotted on a detailed stereotaxic brain atlas of the rat hypothalamus. Positive sites for any behavioural response cluster into restricted hypothalamic areas. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate or low probabilities of inducing the behavioural response concerned. Each response has its own response area where probabilities are high, although there may be overlap. Even within response areas a distinction can be made between areas in which the response can be induced at relatively high or low threshold current intensities. Lowest threshold sites within electrode tracks are often clustered. In search of neuroanatomical correlates, grooming is related to the distribution of ACTH-immunoreactive neural elements, digging is related to the distribution of efferent fibres from the bed nucleus of the stria terminalis, and circling is related to the distribution of dopaminergic fibres of the nigrostriatal pathway. The results clearly point to the stimulation site being the most important determinant of the evoked behavioural response. Evidently behavioural specificity does exist within the hypothalamus.

Animals↗
PubMed1987

Postpartum aggression in rats does not influence threshold currents for EBS-induced aggression.

Female Wistar rats were tested for aggressive behaviour induced by electrical brain stimulation (EBS) in the lateral hypothalamus. Threshold currents for the induction of aggression were determined on several days before the females were paired with experienced breeder males. Beginning in the second week of pregnancy threshold current values were measured once or twice weekly. No change in thresholds was observed either during pregnancy, the early postpartum period or after weaning. Lactation was the only period during which the females were spontaneously aggressive towards male intruders in their home cage, but not in the EBS cage. Analysis of bite targets revealed no difference between the bite patterns in the postpartum maternal aggression test and the EBS-induced attacks. The results demonstrate that the change in physiological and hormonal status in pregnant and lactating females has no influence on the propensity to attack during EBS. The similarity in wound patterns does not advocate a major difference in the types of aggression studied. We speculate upon the nature of EBS-induced attacks as the activation of a rigid, final pathway of aggression which is rather insensitive to mild modulations.

Aggression↗