Robert C. Collins

Kainic acid induced limbic seizures: metabolic, behavioral, electroencephalographic and neuropathological correlates

Increasing amounts (0.3–12 mg/kg) of kainic acid (KA) were given intravenously to rats and behavioral, electrographic, 2-deoxyglucose autoradiographic and neuropathologic responses were studied. A dose of 12 mg/kg kainic acid caused a stereo-typed sequence of staring spells, wet dog shakes, automatisms — mild limbic convulsions and severe limbic convulsions (rearing, bilateral upper extremity clonus, falling and salivation) that developed over 1–2 h. Smaller doses showed different thresholds for these behavioral phenomena but a similar time course of development. Electrographic seizures in limbic areas were similar to afterdischarges produced with electrical stimulation and their threshold was 4 mg/kg. The earliest electrical changes occurred in the hippocampus and were accompanied by staring spells. Subsequently seizures were synchronized in limbic centers during which mild convulsive activity was seen. Finally electrical seizures appeared in both limbic and surface leads, coincident with severe convulsions. Quantitative deoxyglucose autoradiography showed that the hippocampul CA3 region was most sensitive to metabolic changes. Mild limbic convulsions were associated with increased glucose utilization in the hippocampus, subiculum, pyriform and entorhinal cortices, septum and amygdala. Severe limbic convulsions led to even larger changes in these areas as well as the substantia nigra and part of the thalamus. Neuronal damage was seen without systemic metabolic derangements with a threshold of 7 mg/kg. The regions of neuropathology overlapped with areas of intense seizure activity. These data show that systemic kainic acid preferentially activates seizures in the limbic system, particularly the hippocampus, and that different behavioral concomitants of limbic seizures depend on specific patterns of activation of limbic and extra limbic circuits. A scheme for the anatomic spread of seizures in limbic and non-limbic structures is proposed. A state of ‘limbic status’ underlies the neurotoxicity of kainic acid.

Use of cortical circuits during focal penicillin seizures: An autoradiographic study with [14C]deoxyglucose

Autoradiography with [14C]deoxyglucose was used to study the architectural pattern of glucose utilization in the motor cortex of rats during focal penicillin seizures. The seizure focus was characterized by a well circumscribed area whose metabolic activity was increased 2-3 times normal. This was tightly surrounded by cortex that was normal or slightly depressed. The posterior third of the focus showed an increase in glucose utilization in a columnar pattern with particular accentuation of activity in lamina V. There was a loss of normal activity in lamina IV within the focus and in somatosensory and occipital cortex far behind the focus. This depression was particularly prominent in the ipsilateral barrel field. Increased metabolic activity was found in a small area in contralateral homotopic cortex, in lamina Vb with columns extending above this from lamina IV to the surface. Glucose utilization was accentuated 1.2-1.8 fold in the ipsilateral secondary somatosensory area, but was normal in the contralateral cortex. The intensity of focal seizures was increased by the intracortical injection of more penicillin or by giving intravenous metrazol. Both of these methods resulted in an increase in the size of the focus as determined with [14C]deoxyglucose. This was most prominent on the lateral border in lamina I-II and V. In addition, there was an accentuation of the columnar pattern in the posterior part of the focus, ipsilateral somatosensory cortex, and contralateral motor cortex. The architectural pattern of glucose utilization in the cortex during focal seizures is discussed with reference to corticocortical, commissural, and corticothalamic circuits that have been identified by others in anatomical studies. Superimposed on this structure are physiological principles of recurrent excitation, lateral spread, and surround inhibition that characterize basic electrophysiological mechanisms of epilepsy, and influence the intensity of activity within the architectural design.

Kindling of neuroanatomic pathways during recurrent focal penicillin seizures

Sequential changes in convulsive phenomena have been studied using intracortical injections of penicillin as a kindling agent. Rats given 25 units of penicillin every 4 days had a progressive increase in the frequency of contralateral muscle jerks. Unilateral tonic-clinic events began after the third injection, and bilateral jerks of both upper extremities began subsequent to that. No generalized convulsions occurred, and further changes in focal convulsions stopped after 7 injections. The seizure events occurring in this kindled state could be seen in rats given a single injection of 100 units of penicillin. Rats subjected to daily injections at this dosage did not develop more intense seizures, and afterdischarges essentially stopped after the first injection. Animals studied with deoxyglucose autoradiography during kindling with 25 units showed an increase in the size and intensity of metabolic activity in the seizure focus. In addition there was an increase in size and intensity of most transynaptic sites, with new activity appearing in contralateral basal ganglia. A comparison of these findings with the autoradiographic results of animals receiving 100 units of penicillin suggests that the major change during kindling takes place in the focus itself. The appearance of new activity in contralateral basal ganglia is probably an expression of activity in crossed corticostriate pathways from the focus as well as pathways descending from the homotopic cortex in an obligatory input-output response. Use of these pathways is not dependent on kindling, but is available on a first come basis if the intensity of discharges from the seizure focus is strong enough.

Cerebral metabolic response to systematic kainic acid: 14-C-deoxyglucose studies

Abstract Kainic acid (KA) given once intravenously in a dose of 12 mg/kg results successively in staring spells, wet dog shakes, and overt behavioral convulsions over a 90 minute time period. Convulsions last up to 18 hours and are followed by aphagia, adipsia and startle. behavior. Five minutes after KA, deoxyglucose autoradiography reveals a 3–6 fold increase in glucose utilization in ventral CA3 of hippocampus, ventral subiculum, lateral septum with a less intense increase in dorsal hippocampus. During severe behavioral convulsions the entire limbic system and its subcortical projections are metabolically active, while sensory pathways and neocortex are depressed. One to three days following convulsions many limbic areas that participated in seizures are necrotic, while metabolism in the rest of the brain has returned toward normal.

Effects of dopaminergic stimulation on functional brain metabolism in rats with unilateral substantia nigra lesions

Abstract We have studied regional cerebral glucose utilization (RCGU) in awake, unrestrained rats 21 days after unilateral substantia nigra lesions following treatment with either apomorphine (0.5 mg/kg s.c.) or d -amphetamine (2.5 mg/kg s.c.). In ‘control’ rats with a unilateral SN lesion, there was a 30–40% increase in RCGU in the ipsilateral globus pallidus (GP) and a 15–25% increase in the ipsilateral lateral habenular nucleus (LH). Apomorphine treatment produced contralateral while d -amphetamine elicited ipsilateral turning in the lesioned rats. Apomorphine administration led to an increase in RCGU in the ipsilateral striatum, entopeduncularis (EP), and substantia nigra pars reticulata (SNPR); while d -amphetamine elicited similar changes in the same structures contralateral to the lesion. Both apomorphine and d -amphetamine treatment led to bilateral increases in RCGU in the subthalamic nuclei. The increased RCGU found in the ipsilateral GP in ‘lesioned controls’ was reduced to control levels by apomorphine administration, while amphetamine treatment increased RCGU in the contralateral GP without affecting glucose utilization in the ipsilateral GP. Furthermore, apomorphine treatment markedly reduced RCGU in the LHN bilaterally while amphetamine reduced RCGU only in the contralateral LHN. The effects of apomorphine were dose-dependent. Haloperidol (1 mg/kg s.c.) pretreatment completely blocked the development of asymmetric changes in RCGU in nigral lesioned rats after apomorphine administration. These results suggest that apomorphine, a direct dopamine agonist, selectively activated basal ganglia pathways ipsilateral to substantia nigra lesion by interacting with supersensitive dopamine receptors in the ipsilateral striatum. In contrast, d -amphetamine, an indirect dopamine agonist, selectively activated pathways in the contralateral basal ganglia by releasing endogenous dopamine from the intact nigrostriatal pathway. Furthermore, the data suggest that striatal efferents to the GP are not controlled in the same manner as efferents to the EP and SNPR. Finally, these asymmetric changes in RCGU in basal ganglia structures produced by apomorphine or d -amphetamine do not appear to be a consequence of the turning behavior, but rather appear to be proximate effects of the drugs administered.

Cerebral glucose utilization: comparison of [14C]deoxyglucose and [6-14C]glucose quantitative autoradiography.

Abstract: The [14C]deoxyglucose [Sokoloff et al., J. Neurochem.28, 897–916 (1977)] and [6‐14C]glucose [Hawkins et al., Am. J. Physiol.248, C170‐C176 (1985)] quantitative autoradiographic methods were used to measure regional brain glucose utilization in awake rats. The spatial resolution and qualitative appearance of the autoradiograms were similar. In resting animals, there was no significant difference between the two methods among 18 gray and three white matter structures over a fourfold range in glucose utilization rates (coefficient of correlation = 0.97). In rats given increasing frequencies of photoflash visual stimulation, the two methods gave different results for glucose utilization within visual pathways. The linearity of the metabolic response was studied in the superior colliculus using an on‐off checkerboard stimulus between 0 and 33 Hz. The greatest increment in activity occurred between 0 and 4 Hz stimulation with both methods, probably representing recruitment of neuronal elements into activity. Above 4 Hz, there was a progressive increase in labeling with [14C]de‐oxyglucose up to 1.7 times control at 33 Hz. With [6‐14C]‐glucose, there was no further increment in change above a 30% increase seen at 4 Hz. Measurement of tissue glucose revealed no drop in the visually stimulated structures compared to control. We interpret these results to indicate that, with increasing rates of physiological activity, the products of deoxyglucose metabolism accumulate progressively, but the products of glucose metabolism are removed from brain in 10 min.

Functional anatomy of occipital lobe seizures An experimental study in rats

Small amounts of penicillin were used to create a seizure focus in the primary visual cortex (area 17), extrastriate cortex (area 18 and 18a), and neighboring somatosensory and temporal areas in rats. Autoradiography with 14C-deoxyglucose was used to map the focus and the local cortical and long subcortical circuits. Mild seizures from area 17 were associated with focal spiking without behavioral manifestations. There was restricted utilization of local U-fiber circuits and ipsilateral subcortical visual system nuclei. Stronger seizures filled up the visual cortex and projected into adjacent neocortex and limbic cortex, the contralateral 17–18a border, and additional subcortical nuclei. Seizures originating in the posterior visual cortex were associated with prolonged afterdischarges and stereotyped behavioral manifestations, with spread into the posterior cingulum, the subicular complex, and the bilateral hippocampus. After analyzing the eleetrographic discharges, behavior, and seizure pathways in each animal, we conclude that ictal symptoms associated with seizures would not be the expression of the function of a cortical focus, but rather of the dysfunction of excessive discharges through many local and long circuits.

Neurologic manifestations of intravascular coagulation in patients with cancer. A clinicopathologic analysis of 12 cases.

Among 1,459 autopsied patients with cancer, 12 had multifocal infarcts of the brain that appeared to be caused by intravascular coagulation. Most of these patients were women with leukemia or lymphoma, and all had a clinical course in which neurologic signs and symptoms were prominent. All had evidence of generalized brain disease (delirium and stupor or coma), and several also had focal brain disease (focal seizures, hemiparesis). All patients had laboratory evidence of coagulation abnormalities, although these were often not severe when neurologic symptoms began. Pathologically, there were multifocal hemorrhagic or ischemic infarcts in the distribution of several cerebral vessels, without a systemic source for cerebral emboli. Fibrin thrombi were identified in cerebral vessels and in vessels of several other organs. The clinical findings fit the pathologic picture, and in most instances the correct diagnosis might have been made earlier had it been considered.

Distribution of Cytochrome Oxidase in Rat Brain: Studies with Diaminobenzidine Histochemistry in vitro and [14C]Cyanide Tissue Labeling in vivo

Studies in experimental animals and postmortem studies in humans have indicated that the level of the mitochondrial enzyme cytochrome oxidase within brain anatomical pathways is regulated by the long-term functional use of those pathways. To study this relationship, we have measured cytochrome oxidase spectropho-tometrically in punch biopsies from different brain regions of rat. We compared these assays against results from the diaminobenzidine histochemical technique. We found a high degree of correlation (r = 0.90) between the density of diaminobenzidine reaction product and enzyme activity. This validates the usefulness of the diaminobenzidine technique for anatomical localization and measurement of this enzyme. To study the feasibility of using radioactive cyanide as an in vivo ligand of cytochrome oxidase, we performed quantitative autoradiographic analysis of rat brains of animals given an intravenous bolus injection of [14C]cyanide. Analysis of the arterial blood curve indicated a complex redistribution of cyanide between red blood cells, plasma, and tissues. Brain labeling reached peak levels at 1 min and then fell despite rising concentrations of free plasma cyanide. Analysis of autoradiographic images revealed good anatomical resolution. The density of labeling in individual structures over time failed to show a strong correlation with cytochrome oxidase activity or diaminobenzidine reaction product.

Recovery from unilateral neglect

Spontaneous recovery of function occurs in the syndrome of hemisensory neglect in monkeys. We produced this syndrome in 13 macaques by unilateral operative resection of the frontal polysensory association cortex. Using standardized behavioral measures, we documented severe acute neglect and followed the course of its improvement. Using the 2-deoxy[14C]glucose autoradiographic method, we studied animals in the acute phase of neglect and found decrements in local glucose utilization in subcortical structures, but not in cortical regions with known frontal connections. After spontaneous behavioral recovery, mild local glucose utilization decrements remained, but only in nucleus medialis dorsalis of the thalamus. The findings suggest that acute behavioral symptoms are based on widespread depression of neuronal activity in uninjured structures with synaptic relations to damaged cortex, and that return of neuronal activity in those structures is accompanied by restitution of behavioral function.