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Biomedical subjects

M E Corcoran

Publications and source records attributed to M E Corcoran.

At least 91 records · Page 5Linked to original sources
PubMed1978

Antiepileptic and prophylactic effects of tetrahydrocannabinols in amygdaloid kindled rats.

The antiepileptic and prophylactic effects of delta9-tetrahydrocannabinol (delta9-THC) and delta8-THC were examined in rats that developed generalized seizures in response to intermittent electrical stimulation of the amygdala (kindling). Both isomers of the THC were able to acutely suppress kindled seizures, but consistent antiepileptic effects were obtained only with high, toxic dosages. Tolerance to the antiepileptic effects of THC developed very rapidly when the drugs were give repeatedly, and there was evidence that the repeated administration of a high dosage of delta9-THC resulted in a state of acute physical dependence. Administration of the isomers of THC during seizure development resulted in a suppression of kindling, suggestive of a prophylactic effect. The rate of rekindling after withdrawal of the drugs was not significantly different from that of vehicle-treated control rats, however, indicating that a genuine prophylactic effect was not obtained.

Amygdala↗
PubMed1977

On the role of ascending catecholaminergic systems in intravenous self-administration of cocaine.

The role of ascending noradrenergic (NA) and dopaminergic (DA) systems in intravenous self-administration of cocaine in rats was investigated by examining the effects of 6-hydroxydopamine-induced lesions of these systems on responding for the drug on a FR-1 schedule of reinforcement. Lesions of the dorsal and ventral NA bundles that reduced hippocampal-cortical NA by 96% and hypothalamic NA by 72% failed to have any effects on responding for cocaine. Lesions of the nucleus accumbens that reduced the DA content of this nucleus by 90% resulted in a significant and long-lasting (15 days) reduction in self-administration of cocaine. Apomorphine self-administration was not affected in the same animals. Identical lesions of the n accumbens had only transient (2-3 days) effects on food-reinforced operant responding, suggesting that the prolonged disruption of cocaine self-administration was not the result of motor deficits. The results are discussed with reference to the possibility that DA terminals in the n accumbens may mediate some of the positive reinforcing properties of cocaine.

Animals↗
PubMed1977

Hypnotic susceptibility and personality: the consequences of diazepam and the sex of the subjects.

It was suggested by Gibson & Curran (1974) that the rather complex relationships found to obtain between hypnotic susceptibility and the personality parameters of extraversion and neuroticism might be understood by considering neuroticism as a moderator variable (as had been suggested by Furneaux & Gibson, 1961). They made the hypothesis that if a tranquillizing drug were administered the operative level of neuroticism would be decreased, and as a consequence the level of susceptibility of neurotic extraverts would be raised, and that of neurotic introverts lowered. This study reports the test-retest data on a sample of 71 subjects on the Stanford Hypnotic Susceptibility Scales, half of whom were retested with diazepam and half with nicotinic acid. The hypothesis was confirmed and additional data are given on the drug/placebo effects on each item of the scale. The significance of drugs on different aspects of hypnotic susceptibility in relation to personality is discussed.

Diazepam↗
PubMed1976

Attenuation of self-stimulation from substantia nigra but not dorsal tegmental noradrenergic bundle by lesions of sulcal prefrontal cortex.

Rats that self-stimulated from electrodes implanted in either the substantia nigra pars compacta (SNC) or the dorsal tegmental noradrenergic bundle (DTB) received bilateral electrolytic lesions of the prefrontal cortex dorsal to the rhinal sulcus. Immediately after the lesions, animals with SNC electrodes (n = 9) showed significant and permanent reductions in self-stimulation rates. The average reduction in the SNC group was 67% of prelesion bar-pressing scores. In contrast, rats with DTB electrodes (n = 11) were not significantly affected by similar sulcal lesions. Subsequent examination of the brains for prograde degeneration using procedure I of Fink and Heimer 11 revealed a descending system of sulcal efferents that was very dense in the region of the SNC but only scattered in the area of the DTB. The close relation between the effects of sulcal lesions on self-stimulation and the resultant density of degeneration as a function of stimulation site is discussed in terms of the contribution of prefrontal cortex to self-stimulation in general, and of the implications for the catecholamine hypothesis of self-stimulation in particular.

Animals↗
PubMed1976

Acute anticonvulsant effects of diphenylhydantoin, phenobarbital, and carbamazepine: a combined electroclinical and serum level study in amygdaloid kindled cats and baboons.

This preliminary study utilizing the kindling model of established epilepsy has provided information about the most effective routes of administration for diphenylhydantoin, phenobarbital, and carbamazepine in baboons and cats. The time of peak plasma levels for these drugs has been demonstrated in these animals so that experimental protocols can be designed to deliver the agents at appropriate times prior to the kindling stimulation. In addition, dose-effectiveness data is presented for these species. In 1 baboon, phenobarbital was also seen to suppress photosensitive seizures. The potential usefulness of the kindling model in anticonvulsant research is suggested.

Amygdala↗
PubMed1975

Frontal lobe and kindling in the rat.

To test the hypothesis that the cortex participates in amygdaloid kindling in rats, bilateral aspiration lesions were made in various cortical areas in rats prior to kindling. Lesions in orbital cortex (on the dorsal lip of the rhinal sulcus) or prefrontal cortex (area 10) significantly retarded the rate of amygdaloid kindling; lesions in motor cortex, anterior cingulate cortex, or visual cortex were without effect. Detailed analysis indicated that the orbital lesioned and frontal-lesioned rats kindled relatively normally up to the second-last stage of amygdaloid kindling, in which stage they perseverated significantly longer than the controls and the other lesioned rats. These results suggest that areas of the frontal lobe participate in the elaboration and generalization of amygdaloid seizures in rats. Although retarded in rate, kindling nonetheless occurred in the lesioned rats, indicating that these cortical areas are not essential for the development of amygdaloid seizures.

Action Potentials↗
PubMed1975

Effects of taurine on kindled amygdaloid seizures in rats, cats, and photosensitive baboons.

Acute administration of taurine produced a transient loss of susceptibility to photically induced seizures in photosensitive baboons, but failed to affect kindled amygdaloid convulsions in baboons, rats, and cats. In addition, it was totally ineffective in changing the course of spontaneous status epilepticus in kindled cats. These results suggest that a taurine-deficiency model of epilepsy applies only to certain types of seizure-generating conditions, apparently excluding kindled amygdaloid convulsions.

Amygdala↗
PubMed1975

Effects of tetrahydrocannabinols on kindled amygdaloid seizures and photogenic seizures in Senegalese baboons, Papio papio.

Intraperitoneal injections of delta 8-tetrahydrocannabinol (THC) and delta 9-THC failed to affect myoclonic response to photic stimulation in Senegalese baboons (Papio papio). However, both isomers of THC exerted dose-related antiepileptic effects upon established kindled convulsions provoked by electrical stimulation of amygdala in the same species. Delta 9-THC was more potent than delta 8-THC, in terms of both antiepileptic effects and general toxicity. The antiepileptic effects of the THC isomers appear to be due mainly to the suppression of propagation of the induced afterdischarge to distant cerebral structures, although high doses also seem to suppress afterdischarge at the site of stimulation.

Amygdala↗
PubMed1975

Antiepileptic and prophylactic effects of tetrahydrocannabinols in amygdaloid kindled cats.

Acute administration of delta8-tetrahydrocannabinol (delta8-THC) or delta9-THC failed to affect partially developed or fully developed kindled amygdaloid seizures in cats. However, delta9-THC was quite effective in suppressing focal AD in the stimulated amygdala when administered very early in kindling, before the development of any clinical manifestations. This finding suggested that chronic administration of delta9-THC during kindling might block the process of seizure development, which was supported by the observation that three of four cats failed to kindle when treated with the drug. The cat that failed to be protected by delta9-THC was also insensitive to the general electroclinical effects of moderately high doses of delta9-THC. The prophylactic activity of delta9-THC is in contrast to the ineffectiveness of diphenylhydantoin, a drug whose anticonvulsant activity is often compared with that of THC.

Amygdala↗
PubMed1975

Personality and differential susceptibility to hypnosis: further replication and sex differences.

Following the study of Gibson & Curran (1974), a further sample of 45 subjects were tested on the Eysenck Personality Inventory (EPI) and a slightly modified form of the Stanford Hypnotic Susceptibility Scale (SHSS) in precisely the same way. The results in this second sample were broadly the same as those obtained in the earlier study. Combining the two samples, it was found that the sex variable provided some interesting contrasts. The power of the lie scale of the EPI to predict hypnotic susceptibility observed earlier was found to be a significant effect only for males. While there was no significant difference between the sexes in terms of the means and S.D.S. of the extraversion (E) and neuroticism (N) scales, when the interaction of these scales was studied males and females differed significantly. The population from the two studies (n = 88) was analysed by means of polar coordinates in the manner suggested by Eysenck (1966) with regard to the E nad N scales. Esyenck's prediction as to hypnotic susceptibility was strikingly confirmed. These data are briefly discussed in terms of alternative approaches to hypnosis from the 'state' and the 'non-state' viewpoints.

Deception↗