M E Corcoran

The University of Western Ontario, London, Ontario, Canada

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Publications (45)154.33 Total impact

  • D P Cain, F Boon, M E Corcoran
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    ABSTRACT: D-Tyr-Ser-Gly-Phe-Leu-Thr (DSLET), beta-endorphin, morphiceptin and morphine were microinjected at 48-h intervals into the amygdala or hippocampus of awake rats in an attempt to identify the opiate receptor types involved in opioid kindling. DSLET, beta-endorphin, morphiceptin and morphine were injected into the lateral ventricle to assess the possibility of kindling seizures by this route. The delta-receptor agonist DSLET effectively kindled convulsions when microinjected into amygdala or ventral hippocampus. The convulsions were suppressed or strongly attenuated by ICI 174,864, a specific antagonist of the delta-receptor, microinjected into the same brain site, but were not affected by ICI 174,864 administered peripherally. When microinjected into amygdala or hippocampus, beta-endorphin and morphiceptin also kindled convulsions, which were antagonized by naloxone but not by ICI 174,864. Morphine evoked EEG epileptiform activity but did not kindle convulsions from limbic brain sites. DSLET occasionally evoked epileptiform spiking and submaximal convulsions when injected into ventricle, and morphiceptin evoked epileptiform spiking only, but tolerance to these effects occurred after repetition of the injections. Thus, convulsions can be kindled by activation of either mu-, delta- or epsilon-receptors when opioids are injected directly into limbic tissue. However, the ability of these compounds to kindle seizures is markedly reduced when they are administered into ventricle. The striking differences between the present results and previous results obtained by peripheral or intraventricular administration of opioid peptides suggest that the route of administration, among other variables, is a crucial factor in assessing the epileptogenic properties of opioid peptides.
    Brain Research 06/1990; 517(1-2):236-44. · 2.88 Impact Factor
  • D P Cain, A Raithby, M E Corcoran
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    ABSTRACT: The effect of anesthetic and subanesthetic doses of urethane on the development of amygdala kindled seizures and on the expression of previously kindled seizures was studied in hooded rats. An anesthetic dose of urethane (1.5 g/kg) almost completely eliminated evoked afterdischarge and completely eliminated convulsive behavior in both groups. It also eliminated the seizure response to pentylenetetrazol. Subanesthetic doses of urethane (0.25 and 0.5 g/kg) strongly attenuated the expression of previously kindled seizures. These results suggest that urethane may not be an appropriate anesthetic for the study of epileptiform phenomena.
    Life Sciences 02/1989; 44(17):1201-6. · 2.56 Impact Factor
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    ABSTRACT: Rats were electrically kindled in deep prepyriform cortex (DPC) and in immediately surrounding areas, pyriform cortex, and the basolateral amygdala in an effort to identify an area of the basal forebrain crucially involved in epileptogenesis and the kindling of seizures. Picomolar quantities of carbachol were also microinjected into DPC. All of these areas kindled at equivalent rates. Injection of picomolar quantities of carbachol failed to evoke epileptiform spiking, but injection of nanomolar quantities of carbachol usually evoked epileptiform spiking. Bilateral radiofrequency lesions of the DPC did not affect the rate of electrical kindling of the basolateral amygdala. We conclude that the DPC kindles readily at a rate that is similar to that of surrounding basal forebrain tissue and that the integrity of the DPC is not necessary for basolateral amygdaloid kindling.
    Experimental Neurology 05/1988; 100(1):203-9. · 4.65 Impact Factor
  • D P Cain, J Plant, S Rouleau, M E Corcoran
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    ABSTRACT: In an attempt to kindle seizures with arginine-vasopressin (AVP), we injected AVP into the amygdala or hippocampus of rats. Although behavioral and electrographic alterations were sometimes observed, seizures failed to develop, even in rats that had previously been kindled with electrical stimulation. This and previous failures to kindle seizures by intraventricular injections of AVP call into question the possibility of AVP kindling.
    Life Sciences 04/1986; 38(11):985-9. · 2.56 Impact Factor
  • D P Cain, M E Corcoran
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    ABSTRACT: Repeated spaced injection of small amounts of beta-endorphin or Met-enkephalin into the hippocampus or posterior amygdala of the rat led to the development of kindled generalized convulsions. Similar injection of morphine into the hippocampus or anterior amygdala resulted in epileptiform spiking followed by tolerance. The epileptiform spiking and convulsive behavior varied in a dose-related manner. Naloxone blocked or greatly attenuated the electrographic seizure and convulsive behavior. Prior kindling with beta-endorphin or Met-enkephalin significantly facilitated electrical kindling of the amygdala. Handling or conspecific threat potentiated the epileptiform spiking and convulsive behavior in some cases. The results indicate that the epileptogenic response to intracerebrally applied opioid peptides is site-specific within the rat brain, and they support the idea that endogenous opioid mechanisms may play a role in convulsive seizures. They also suggest a possible opiate-based mechanism for the stress-induced exacerbation of seizures.
    Brain Research 08/1985; 338(2):327-36. · 2.88 Impact Factor
  • M E Corcoran, D P Cain, J M Finlay, B J Gillis
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    ABSTRACT: In an attempt to confirm a previous report that two intracerebroventricular injections of arginine-vasopressin (AVP) can kindle convulsive seizures, we injected AVP up to 14 times. Although behavioral and electrographic effects were observed, seizures failed to develop with any reliability. These results call into question the phenomenon of AVP kindling.
    Life Sciences 09/1984; 35(9):947-52. · 2.56 Impact Factor
  • D P Cain, M E Corcoran
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    ABSTRACT: The effects of repeated infusion of small, initially subconvulsive amounts of beta-endorphin, met-enkephalin or morphine sulfate into the amygdala and hippocampus were investigated. beta-endorphin and met-enkephalin evoked epileptiform spiking when infused into the posterior amygdala or ventral hippocampus. Morphine evoked epileptiform spiking when infused into the anterior amygdala. Naloxone blocked or terminated the spiking. Repetition of the infusions led to the gradual development of bilateral generalized convulsions by beta-endorphin and met-enkephalin and to the development of tolerance to morphine. An unexpected observation was that handling, immobilization or conspecific threat potentiated the epileptiform effects of beta-endorphin and morphine in many cases. These results suggest that endogenous opiate mechanisms might play a role in convulsive seizures and that stressful stimuli can exacerbate opiate seizures.
    Life Sciences 07/1984; 34(25):2535-42. · 2.56 Impact Factor
  • M E Corcoran, D P Cain, J A Wada
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    ABSTRACT: Three baboons, Papio cynocephalus, (two photosensitive and one nonphotosensitive) were subjected to amygdaloid kindling. Electroclinical profile of seizure development-developed seizure compares very favourably to that described in photosensitive baboons, Papio papio, with rapid seizure progression and ultimate emergence of Stage 5 bisymmetrical and bisynchronous generalized convulsive state. In addition, one baboon developed spontaneous recurrent seizures which were identical to the kindled Stage 5 seizure. It is concluded that the state of exceptional seizure susceptibility observed in Papio papio is shared by Papio cynocephalus, although photosensitivity and kindled generalized convulsion appear to be independent variables.
    Folia psychiatrica et neurologica japonica 02/1984; 38(2):151-7.
  • D P Cain, M E Corcoran
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    ABSTRACT: Rats were stimulated in the amygdala, dorsal and ventral hippocampus, pyriform cortex, and preoptic area with low-frequency square-wave pulses at gradually increasing intensities until a generalized seizure occurred. Stimulation at 3.0 Hz was effective for rapidly kindling generalized seizures in all structures studied. Subjects stimulated in the amygdala with frequencies of stimulation between 0.875 and 10.0 Hz also kindled rapidly and exhibited rapid transfer to the contralateral amygdala. Some subjects kindled in one trial. Strong recruiting occurred in response to stimulation at frequencies between 0.875 and 10.0 Hz and invariably preceded the development of kindled seizures. These results suggest that low-frequency stimulation is more effective than high-frequency stimulation in inducing seizure development in a variety of forebrain sites.
    Experimental Neurology 08/1981; 73(1):219-32. · 4.65 Impact Factor
  • M Pisa, P R Sanberg, M E Corcoran, H C Fibiger
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    ABSTRACT: Intrastriatal injection of kainic acid in rats acutely induced repeated episodes of clonic convulsions. Spontaneously recurrent generalized seizures and a potentiation of the convulsant effects of phentylenetetrazol were then observed in most of the injected rats several weeks after surgery. In addition to marked loss of striatial neurons, limbic pathological alterations similar to those found in human temporal lobe epilepsy were observed in the brains of the kainic-acid treated rats. It is proposed that this preparation might serve as an animal model of human temporal lobe epilepsy.
    Brain Research 12/1980; 200(2):481-7. · 2.88 Impact Factor
  • D P Cain, M E Corcoran
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    ABSTRACT: The kindling response in the amygdala of each of two strains of Mongolian gerbil bred for resistance to and suceptibility to stress-precipitated seizures was assessed. Seizure-prone gerbils had a lower afterdischarge threshold, a longer initial afterdischarge duration, and required fewer sessions to develop generalized kindled convulsions. Following kindling, the precipitated seizure pattern was exacerbated in both groups. These results suggest that the naturally occurring and kindled seizure states may depend in part on a common neural mechanism in this species.
    Electroencephalography and Clinical Neurophysiology 09/1980; 49(3-4):360-5.
  • M E Corcoran, D P Cain
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    ABSTRACT: Repeated application of electrical stimulation to the amygdala at a frequency of 3 Hz resulted in the development of afterdischarge and behavioral seizures. The rate of low-frequency kindling was faster than that of kindling with conventional 60 Hz stimulation, but the form of the seizures kindled with the two frequencies of stimulation was identical. Low-frequency kindling was obtained only when pulses of sufficient duration and intensity were administered.
    Brain Research 09/1980; 196(1):262-5. · 2.88 Impact Factor
  • D P Cain, M E Corcoran, W A Staines
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    ABSTRACT: Mice treated with anisomycin during amygdaloid kindling failed to develop generalized seizures. Anisomycin failed to suppress fully developed seizures in kindled mice, indicating that its prophylactic effects are not secondary to a general anticonvulsant action. These results are consistent with the hypothesis that the central neuroplastic changes underlying kindling require the ongoing synthesis of proteins.
    Experimental Neurology 07/1980; 68(3):409-19. · 4.65 Impact Factor
  • M E Corcoran, S T Mason
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    ABSTRACT: The rate and pattern of seizure development provoked by repeated electrical stimulation of the amygdala (kindling) was assessed in rats that had been pretreated with intracerebral injections of the selective catecholaminergic neurotoxin 6-hydroxy-dopamine. Rats with selective depletion of forebrain noradrenaline displayed a highly significant facilitation of both primary-site and secondary-site kindling, whereas no such effect occurred in rats with selective depletion of forebrain dopamine. The facilitative effects of noradrenaline depletion were apparently related to disinhibition of the spread of seizure discharge from the stimulated site rather than to increased epileptogenicity in the stimulated site itself. These results are consistent with previous evidence that noradrenaline reduces the susceptibility of the central nervous system to epileptiform activity, and they suggest that a lessening of seizure-suppressant noradrenergic function in the forebrain might be part of the mechanism underlying kindling.
    Brain Research 06/1980; 190(2):473-84. · 2.88 Impact Factor
  • S T Mason, M E Corcoran
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    ABSTRACT: Severe depletion of brain noradrenaline and separately of brain dopamine was induced in rats by intracerebral injection of the selective neurotoxin 6-hydroxydopamine, and the susceptibility of the treated animals to various seizure-inducing manipulations was examined. A significant potentiation of the seizures induced both by Metrazol and by electroconvulsive shock was found in animals depleted of brain noradrenaline, but no alteration was seen after depletion of brain dopamine on either measure. The catecholaminergic drug cocaine also induced seizures, but these were found not to depend on either brain noradrenaline or dopamine as they continued to occur in the virtual absence of either catecholamine. It is concluded that cocaine induces seizures by a non-specific toxic mechanism and that noradrenaline, but not dopamine, is involved in reducing the suceptibility of the central nervous system to the several distinct forms of seizure induction examined.
    Brain Research 08/1979; 170(3):497-507. · 2.88 Impact Factor
  • D P Cain, M E Corcoran, J A Wada, A S Troupin
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    ABSTRACT: The effect of post-trial barbiturate injection on amygdaloid kindling was assessed using two different barbiturates. Hooded rats were stimulated electrically in a standard kindling paradigm, and received one of the barbiturates either immediately following the cessation of afterdischarge (AD) or 2 hr following each stimulation. Appropriate nondrugged controls were also stimulated. Treated animals kindled as rapidly as controls, indicating that undisturbed post-AD neural activity is not crucial for amygdaloid kindling. However, it appears that animals stimulated at long intervals develop seizures significantly faster than those stimulated at shorter intervals, which may indicate that a nonessential but facilitatory process occurs following each evoked afterdischarge.
    Behavioral and Neural Biology 07/1979; 26(2):202-8.
  • M E Corcoran, D P Cain, J A Wada
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    ABSTRACT: Significant susceptibility to photically induced seizures has in the past been observed only in Senegales baboons (Papio papio) and epileptic humans. However, we have unexpectedly observed a photomyoclonic response to intermittent photic stimulation in 5 of a sample of 6 yellow baboons (Papio cynocephalus).
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 06/1979; 6(2):129-31. · 1.33 Impact Factor
  • S T Mason, M E Corcoran, H C Fibiger
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    ABSTRACT: Intracerebral injection of 4 microgram of the neurotoxin 6-hydroxydopamine (6-OHDA) was used to deplete forebrain noradrenaline (NA) in rats to less than 5% of control values without affecting brain dopamine (DA) and the oral consumption of ethanol examined. Control rats showed a progressive increase in their intake of a 15% ethanol solution and after 15 days were consuming large quantities. This increase did not occur in NA depleted rats, which after 15 days had consumed no more than a few millilitres of the solution in total. The results are discussed in terms of a central noradrenergic basis of ethanol reward.
    Neuroscience Letters 05/1979; 12(1):137-42. · 2.03 Impact Factor
  • S T Mason, M E Corcoran
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    ABSTRACT: Intracerebral injection in rats of 4 microgram of the catecholamine neurotoxin 6-hydroxydopamine was used to deplete forebrain noradrenaline to less than 10% of control values and separately to deplete brain dopamine to less than 15% of control. The susceptibility of these animals to electroconvulsive shock-induced convulsions was examined, and a significant potentiation of the response was seen in the rats depleted of noradrenaline but not in those depleted of dopamine. The duration of the convulsion was significantly increased as a result of loss of forebrain noradrenaline.
    Journal of Pharmacy and Pharmacology 05/1979; 31(4):209-11. · 2.03 Impact Factor
  • S T Mason, M E Corcoran
    Brain Research 05/1979; 166(2):418-21. · 2.88 Impact Factor

Publication Stats

1k Citations
154.33 Total Impact Points

Institutions

  • 1980–1990
    • The University of Western Ontario
      • Department of Psychology
      London, Ontario, Canada
  • 1979–1990
    • University of Victoria
      • Department of Psychology
      Victoria, British Columbia, Canada
  • 1973–1980
    • University of British Columbia - Vancouver
      • • Department of Psychiatry
      • • Faculty of Medicine
      Vancouver, British Columbia, Canada