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R E Adamec

Publications and source records attributed to R E Adamec.

12 recordsLinked to original sources
PubMed1991

Partial kindling of the ventral hippocampus: identification of changes in limbic physiology which accompany changes in feline aggression and defense.

This study examined the interictal consequences of partial kindling of the ventral perforant path on attack and defensive behavior in the domestic cat. Partial kindling produced a lasting increase in defense response of cats to both rats and conspecific threat howls. In addition, there was a lasting suppression of approach-attack behaviors directed toward rats. The suppression of some components of approach-attack were shown to be independent of the increases in defensive response. The effects of partial kindling of the ventral perforant path on spread of seizure activity into the amygdala, and on the output of the amygdala to both the ventromedial hypothalamus (VMH) and bed nucleus of the stria terminalis (BNST) were also examined. In addition, the effects of repeated hippocampal seizures on recurrent inhibition in the trisynaptic circuit (areas CA1 and CA3) were investigated. Growth of seizure activity in the amygdala and VMH as partial kindling progressed was essential for behavioral change. In addition, interictal long-term potentiation of potentials evoked in the VMH and in the BNST by pulsed stimulation of the amygdala followed partial kindling or afterdischarge threshold determination in the ventral perforant path. A lasting interictal increase in inhibition in area CA3 and a lasting interictal failure of inhibition in area CA1 of the ventral hippocampus also followed partial kindling. These changes in limbic physiology were related to the behavioral changes produced by partial kindling. The analysis revealed the importance of the amygdalo-VMH pathway in increased defensive response to rats. The amygdalo-BNST pathway is not important in mediating defensive response to prey, but it is implicated in suppression of some types of predatory aggression. Finally, changes in neural inhibition in the ventral hippocampus in areas CA1 and CA3 are associated with changes in both defensiveness and predatory aggression.

Aggression↗
PubMed1991

Individual differences in temporal lobe sensory processing of threatening stimuli in the cat.

In Experiment I, neurosensory responses from three limbic areas in the cat brain were recorded when cats of differing defensive temperamental traits were exposed to species characteristic threat. The cats investigated were more or less defensive in response to rats and conspecific threat howls. The behavioral disposition of these cats was stable over retest periods of more than one year. It was found that during visual inspection of rats, more defensive cats displayed greater neural activity in the amygdala and the ventromedial hypothalamus than less defensive cats, who showed no change over baseline. Neurosensory response of the amygdala to conspecific threat howls was also found to be greater in more defensive cats. In contrast, there was no neural response to threat howls in the hypothalamus. Neurosensory response to mice was different from the response to rats and threat howls. Visual inspection of the mouse was associated with a decrease in activity in the amygdalas of more defensive cats. Finally, response of the ventral hippocampus was unspecific, appearing to signal only a change in the stimulus environment. The increase in hypothalamic neural activity in response to rats in more defensive cats appeared to be driven by a potentiated output from the amygdala, since the ratio of hypothalamic to amygdala neurosensory response to rats was greater than one in more defensive cats, but equal to one in less defensive cats. Output of the amygdala was directly investigated using evoked potential techniques in Experiment II. Potentials evoked in the hypothalamus by amygdala stimulation were larger in more defensive cats. Size of the hypothalamic potential was highly correlated with the ratio of hypothalamic to amygdala neurosensory response (ratio response) to rats. Removing the effects of size of the hypothalamic evoked potential from the ratio response by analysis of covariance eliminated the difference between more and less defensive cats in ratio response to rats. The significance of these findings for the physiological bases of defensive response to threat and of temperamental traits are discussed.

Aggression↗
PubMed1990

Does kindling model anything clinically relevant?

In this theoretical review, the value of the kindling phenomenon in enhancing our understanding of clinical disorders associated with epilepsy is evaluated. The kindling phenomenon is first described. Kindling is suggested to be a viable model of complex partial seizure (CPS) disorders with secondary generalization. Moreover, it is shown how kindling has been used as a conceptual tool which suggests novel psychiatric therapies. Finally, the value of kindling as a model of psychopathology associated with limbic epilepsy is discussed. It is concluded that studies of the effects of kindling on emotional behavior may offer a model of how limbic seizures in humans increase the vulnerability of patients to external precipitants of psychopathology, including anxiety and depression. Studies of the effects of kindling on dopaminergic function are also reviewed. This line of investigation holds promise for enhancing our understanding of hyperdopaminergic consequences of limbic epilepsy. Furthermore, these studies have created testable hypotheses that may explain the complex relationship between epilepsy and psychosis.

Animals↗
PubMed1987

The effects of procaine HCl on population cellular and evoked response activity within the limbic system of the cat. Evidence for differential excitatory action of procaine in a variety of limbic circuits.

1. The effects of intravenous injections of procaine HCl on population cellular activity in limbic tissue and overlying cortex, and on transmission of evoked activity between limbic structures was investigated in awake cats. Clear dose-related increases in cellular activity were seen in amygdala and ventral hippocampus. Changes in cellular activity in the nucleus accumbens and temporal neocortex were also dose-related, but in a complex time-dependent manner. Changes in ventromedial hypothalamus only appeared at the second highest dose of procaine. 2. Procaine facilitated transmission of evoked excitatory activity from the amygdala to the ventromedial hypothalamus, but only after a considerable delay from the time of injection. On the other hand, procaine had no effect on activity evoked in the ventral hippocampus, nucleus accumbens or temporal cortex by amygdala stimulation. 3. It was concluded that intravenous procaine functions as an excitant of limbic system cells, and that procaine alters synaptic transmission in some, but not all, output pathways from the amygdala. The neuroexcitant effects of procaine appear to be idiosyncratic, however, varying over dose with limbic and cortical area examined.

Amygdala↗
PubMed1985

Basic science and clinical aspects of procaine HCl as a limbic system excitant.

The literature in animals and humans which indicate that systemic procaine HCl activates limbic tissue is reviewed. Studies in cats which suggest that procaine excites limbic cells by reducing neural inhibition are then described. Evidence that power spectral analysis of high frequency EEG bands (omega or 31-55 cps) in the temporal cortical EEG reflects degree of limbic (amygdala) excitation in animals and humans is reviewed. Studies in cats are described which show that procaine selectively increases omega band activity in the amygdala and temporal cortex in a dose related fashion which parallels dose related increases in amygdaloid neural activity. Preliminary results of combining intravenous procaine and omega band analysis of scalp EEG in humans to predict therapeutic response to carbamazepine in borderline personality and affective disorder patients are then described. The effects of procaine on omega are compared to the effects of direct electrical stimulation of human limbic system in complex partial seizure patients undergoing assessment for temporal lobectomy. The results tentatively support the hypothesis that some psychiatric patients have hyperexcitable limbic systems, and those that do, show a positive behavioural response to carbamazepine.

Animals↗
PubMed1976

Hypothalamic and extrahypothalamic substrates of predatory attack. Suppression and the influence of hunger.

Electrical stimulation of medial hypothalamic and ventromedial hypothalamic areas of the cat brain stops the initiation of spontaneous predatory attack in cats, confirming similar evidence of other investigators. Furthermore, a new attack suppressing area, the mammillary bodies, was uncovered. Facilitation of predatory attack by hunger raised the electrical threshold for attack in the mammillary bodies. In addition, baseline levels of neural activity in attack suppressing brain areas prior to any brain stimulation were found to decrease when the cats were hungry and killing was facilitated and neural activity increased when the cats were on ad lib. feeding. These data support the hypothesis that modulation of excitability of neural systems functioning to suppress is involved in facilitation of attack behavior by hunger.

Animals↗
PubMedDate not supplied

Amygdala kindling and anxiety in the rat.

In humans, limbic epilepsy seems to predispose to anxiety. Attempts to model this phenomenon have shown that limbic kindling increases anxiety in domestic cats. No comparable data exist in rodents. The present study was done to investigate the effects of unilateral medial amygdala kindling in Wistar rats on behaviour in the 'elevated plus maze' test of anxiety. It was found that kindling to stage 5 seizures increased anxious response in the plus maze for at least a week following the last seizure. There were equally long lasting decreases in exploratory motivation in the hole board test, which were unrelated to the change in anxiety in the plus maze. The relevance of these findings to epilepsy, stress and anxiety are discussed.

Amygdala↗