Effects of dexamethasone and of local hypothermia on early and late tissue electrolyte changes in experimental spinal cord injury.

The current experiment reexamines this laboratory's frequently cited previous experimental conclusion that a mechanism underlying the beneficial effects of glucocorticoids in the treatment of spinal cord injury may be the enhanced preservation of spinal cord tissue potassium. For the first time, similar methodology also has been applied to study the effects of hypothermia. Canine spinal cords were injured at T13 by use of an epidural balloon and then were treated with local hypothermia or intramuscular dexamethasone or both. Motor recovery was assessed using a modified Tarlov scale. At either 6 days or 7 weeks, spinal cords T8 through L4 were removed and divided into 10 ordered blocks, which were analyzed for wet and dry weight, potassium concentration, and sodium concentration. Correlations between clinical motor and chemical results were evaluated. The conclusions drawn are as follows: 1) The canine severe rapid compressive injury model, unlike the previously published less severe feline impact injury model, is not associated with widespread early loss of spinal cord tissue potassium content (dry weight). 2) The dog compressive model, unlike the cat impact model, does not provide evidence that one fundamental mechanism of the confirmed beneficial action of steroids entails enhanced early preservation of tissue potassium content. 3) At 6 days, decrease in the percentage of dry weight and increase in sodium concentration, representing edema, occurred at and adjacent to the direct compression site in all lesioned dog groups except those treated with dexamethasone, demonstrating an antiedema effect of dexamethasone that was nullified by concurrent local hypothermia. 4) This antiedema effect of dexamethasone was associated with superior early motor improvement but did not lead to superior long-term function, in comparison with hypothermia. 5) At 7 weeks, decrease in the percentage of dry weight and potassium concentration, and increase in sodium concentration, all restricted to the directly compressed segment, signify necrosis. 6) This new chemical index of necrosis was highly correlated with clinical motor performance.

Cortical hypometabolism in injured brain: new correlations with the noradrenergic and serotonergic systems and with behavioral deficits.

Changes with time after injury in behavioral deficits, as determined by the Morris swim test, and the in vivo specific binding of HEAT, a selective alpha 1-adrenoreceptor ligand, were compared with the time-course of development of cortical hypometabolism in rats with focal freezing lesions. In our trauma model, cortical hypometabolism was detectable in the lesioned hemisphere at 4 hr, became maximal (50% of normal) at 3 days and diminished towards normal on days 5 and 10 post-injury. Progressive impairment of acquisition of the Morris water maze task was demonstrated up to day 3 post-lesion with improvement thereafter. On day 3 the latency to reach criterion was 60% longer in lesioned animals than in corresponding sham-operated ones. An increase in the volume of distribution of HEAT, limited to cortical areas of the lesioned hemisphere, was demonstrable at 4 hr post-lesion and reached its maximum on day 3 (200% of normal) with subsequent return toward normal on days 5 and 10. Several types of drugs were shown previously to modify the cortical hypometabolism associated with cerebral injury. The present data indicate that the same drugs also modify the in vivo binding of HEAT and the behavioral deficits induced by brain lesions. Ibuprofen, a non-steroidal anti-inflammatory drug, p-chlorophenylalanine, an inhibitor of serotonin synthesis, ketanserin, a specific 5HT2-receptor antagonist, and prazosin, an alpha 1-adrenergic receptor blocker all normalized the in vivo binding of HEAT in the cortical areas of the lesioned hemisphere. All groups of animals treated with these drugs also showed subtle, but statistically highly significant improvements in latency to locate the platform in the Morris water maze. Taken together these results show good correlation between behavioral deficits, changes in alpha 1-noradrenergic receptor binding and cortical hypometabolism in injured brain. This supports the hypothesis that post-injury cortical hypometabolism is a reflection of cortical functional depression in which both the serotonergic and noradrenergic neurotransmitter systems play a role, compatible with their inhibitory effects in the cortex and their postulated involvement in cortical information processing.

Local cerebral glucose utilization in stimulated rats sedated with thiopental.

BACKGROUND: Recent studies have suggested that supraspinal structures are involved in barbiturate-induced enhancement of nociceptive processing. The goal of the study was to determine whether cortical and subcortical regions involved in nociception were relatively activated or depressed by noxious stimulation during infusion of small doses of thiopental. METHODS: Local cerebral glucose utilization (LCGU) was measured with the 14C-2-deoxyglucose radioautographic technique in 14 rats. During the LCGU experiment, pressure was applied to the tail every 2 min, and the somatic motor response threshold was recorded. Seven animals received thiopental infusions to produce a steady-state plasma concentration (target concentrations of 10 micrograms/ml), and seven untreated animals served as controls. RESULTS: A steady-state plasma thiopental concentration (11.1 +/- 1.8 to 13.0 +/- 2.1 micrograms/ml) was accompanied by a decrease in the somatic motor response threshold from 277 +/- 32 g (before thiopental) to 215 +/- 41 g (P < 0.001). The somatic motor response threshold remained unchanged in the control group. Average LCGU was 29% less in the thiopental-treated animals than in the untreated controls (P < 0.001). In cortical regions associated with nociception, LCGU was relatively increased (+3% +/- 14%) during the thiopental infusion in comparison to the visual and auditory cortices (-18% +/- 13%; P < 0.001). Individual structures that showed relative changes during thiopental infusion included the nucleus accumbens (+17%, P < 0.05) and the habenula (-17%, P < 0.05). Heterogenous relative changes (P < 0.05) in LCGU were observed in the auditory system: auditory cortex (-22%), medial geniculate (-16%), lateral lemniscus (+26%), superior olive (+38%). CONCLUSIONS: Noxious stimulation during low-dose thiopental infusions relatively increased LCGU in cortical regions postulated to be responsible for processing of noxious stimuli. Nuclei in the descending pain modulating system were not relatively depressed.

Synthesis of serotonin in traumatized rat brain.

Previous studies have demonstrated that focal freezing lesions in rats cause a widespread decrease of cortical glucose use in the lesioned hemisphere and this was interpreted as a reflection of depression of cortical activity. The serotonergic neurotransmitter system was implicated in these alterations when it was shown that (1) cortical serotonin metabolism was increased widely in focally injured brain and (2) inhibition of serotonin synthesis prevented the development of cortical hypometabolism. In the present studies we applied an autoradiographic method that uses the accumulation of the 14C-labeled analogue of serotonin alpha-methylserotonin to assess changes in the rate of serotonin synthesis in injured brain. The results confirmed that 3 days after the lesion was made, at the time of greatest depression of glucose use, serotonin synthesis was significantly increased in cortical areas throughout the injured hemisphere. The increase was also seen in the dorsal hippocampus and area CA3, as well as in the medial geniculate and dorsal raphe, but not in any other subcortical structures including median raphe. Present results suggest that the functional changes in the cortex of the lesioned hemisphere are associated with an increased rate of serotonin synthesis mediated by activation of the dorsal raphe. We also documented by alpha-[14C]aminoisobutyric acid autoradiography that there was increased permeability of the blood-brain barrier, but this was restricted to the rim of the lesion.

Effect of injury on the bi-affinity alpha 1-adrenoreceptor binding in rat brain in vivo.

Focal freezing lesions in rats cause a widespread decrease of cortical glucose utilization in the lesioned hemisphere, probably as a reflection of depressed cortical activity. The noradrenergic neurotransmitter system was implicated in these alterations when it was demonstrated that prazosin, a specific norepinephrine (NE) antagonist at alpha 1-adrenergic receptors, prevented their development. In normal rat brain, specific binding of [125I]HEAT [(+/-)2-(3-[125I]iodo-4-hydroxyphenyl)-ethyl-aminomethyl-tetralone], another selective alpha 1-adrenoreceptor ligand, was demonstrated in vivo at sites consistent with the alpha 1A- and alpha 1B-adrenoreceptor subtypes. In the present study, the effect of a freezing lesion on specific binding of [125I]HEAT in rat brain in vivo was determined three days after traumatization when cortical glucose use suggested the greatest degree of functional depression. The steady-state volumes of distribution of [125I]HEAT three days after injury were significantly increased in all the cortical areas of the lesioned hemisphere, but not in the subcortical structures. Injury did not modify the binding affinities for HEAT. However, a statistically significant increase in the number of low-affinity binding sites for this ligand was demonstrated in all cortical areas of the lesioned hemisphere, but not in subcortical structures. The traumatization did not modify Bmax estimates for the high-affinity binding of HEAT. The results support the hypothesis that changes in the noradrenergic system are of functional importance in brain injury and that at least some effects of injury are mediated by alpha 1B-adrenergic receptors.

[Metabolic effects of experimental thermal damage of the brain in rats--cold lesion]. / Efekty metaboliczne doswiadczalnego, termicznego uszkodzenia mózgu u szczura--cold lesion.

Experimental thermal brain injury leads to significant reduction of glucose utilization in the damaged hemisphere particularly evident in the cortex 3 days after the injury. The rate of development of these changes is not parallel with the observed damage to the blood-brain barrier, coexistent brain oedema and slight disturbances of cerebral blood flow. In a series of experiments it was possible to demonstrate significant accumulation of glucose, high-energy phosphate compounds and their metabolites in the areas of the brain near the damaged part. The authors think that this is an evidence of reduced glucose uptake by the brain resulting from reduced energy needs of the damaged brain tissue despite sufficient supply of energy-yielding substances. Since cerebral metabolism and functions are in close interrelationship reduced glucose metabolism in the damaged tissue leads to reduced activity of the cortex, which contributes to transient (or permanent) functional neurological deficits observed after cranio-cerebral trauma in humans. The knowledge and understanding of these processes regulating the development of local depression of cerebral metabolic processes may help in better results of treatment in such cases.

Bi-affinity alpha 1-adrenoceptor binding in normal rat brain in vivo.

The specific binding in rat brain in vivo of [125I]HEAT ([125I]iodo-2-[beta-(4-hydroxyphenyl)ethylamino methyl), a selective alpha 1-adrenoceptor ligand, was analyzed by a method designed to distinguish sites with different affinities. The data indicate at least two sites with different affinities for the alpha 1-adrenoreceptor in normal rat brain in vivo: a high-affinity site with Kd (half-saturation constant) of 3.6 +/- 0.7 nM (AV +/- SD), and a low-affinity site with Kd of 668 +/- 552 nM. The density (Bmax) of the high-affinity site in nine brain regions--auditory, visual, sensorimotor (four layers) and frontal cortex and lateral thalamic and medial geniculate nuclei--varied from 2.2 +/- 0.8 to 14.6 +/- 0.6 pmole/g, while the low-affinity range was 149 +/- 44 to 577 +/- 30 pmole/g. The results also revealed a very dynamic relationship between the two sites regulated by the concentration of the ligand ranging from 80% preponderance of the high-affinity sites at low ligand concentrations to more than 95% preponderance of the low-affinity sites at high ligand concentrations.

Effects of focal cortical freezing lesion on regional energy metabolism.

Freezing lesions have been shown to cause a depression in glucose use, particularly in cortical areas of the brain ipsilateral to the lesion, and this effect was interpreted to be caused by a depressed functional activity in these regions. The metabolic status of the affected areas has not been previously examined and could be a factor in the observed changes in local CMRglc. In frozen-cut and dried sections taken from brains 3 days after freeze lesioning, discrete pieces of the median and lateral parietal cortex, striatum, hippocampus, and hypothalamus were dissected and analyzed for ATP, P-creatine, glucose, and lactate. CMRglc measurements were also made in the same animals. The concentrations of the four metabolites were significantly increased in the lesioned hemisphere, with the most predominant effects observed in the cortical areas that exhibited the greatest depression in CMRglc. The enriched metabolite profile, particularly in the cortical areas, is consistent with the hypothesis that decreased glucose use in the traumatized brain is caused by diminished need rather than by decreased supply of energy. Because the lumped constant in the operational equation of the deoxyglucose method for determination of CMRglc is a function of brain glucose content and decreases gradually in hyperglycemia, the degree of metabolic depression in cortical areas of lesioned hemisphere probably have been somewhat overestimated in this and previous publications. However, provisionally recalculated local CMRglc in the lesioned hemisphere remain significantly lower than in the contralateral hemisphere and in the normal brain.

Brain injury: new insights into neurotransmitter and receptor mechanisms.

The studies reviewed here represent a continuing search for mechanisms which play a role in neurological disturbances resulting from brain injury. Focal cortical freezing lesions in rats were shown to cause a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity. Such an interpretation was supported by the finding that in lesioned brain reduction of cerebral metabolism by pentobarbital and isoflurane was limited by the metabolic depression that has already occurred as a result of injury and by the demonstration that the energy status and substrate (glucose) supply in the cortical areas in the injured brain have not been compromised at the time when LCGU was decreased. Both the serotonergic and the noradrenergic neurotransmitter systems were implicated in functional alterations associated with injury. Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere and complete inhibition of 5-HT synthesis with p-chlorophenylalanine ameliorated the decrease in cortical LCGU, interpreted as reflecting cortical functional depression. Cortical norepinephrine metabolism was bilaterally increased in focally injured brain, while prazosin, a selective alpha 1-noradrenergic receptor blocker, normalized cortical LCGU in the lesioned hemisphere. Low-affinity in vivo binding of [125I]HEAT, another selective alpha 1-receptor ligand, was specifically increased in cortical areas of the lesioned hemisphere at the time of the greatest depression in LCGU, suggesting that alpha 1-adrenoreceptors may be of functional importance in injured brain.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of alpha-adrenergic receptor blockers prazosin and yohimbine on cerebral metabolism and biogenic amine content of traumatized brain.

Widespread decrease in local cerebral glucose utilization (LCGU) previously shown to occur 3 days after a local freezing lesion was interpreted as reflecting a depression of functional activity in the affected areas. In parallel experiments, cortical norepinephrine (NE) content of traumatized brain was found to be decreased. The effects of prazosin (PZ), an alpha 1-adrenergic receptor blocker, and yohimbine (YOH), an alpha 2-blocker, on glucose use and biogenic amine content of lesioned rat brain were studied to determine if the changes in the noradrenergic system associated with injury are of functional importance, to identify the receptors that may be involved in mediating the action of NE in injured brain, and to look for evidence of interaction between the noradrenergic and the serotonergic systems in traumatized brain. PZ (1 mg/kg) given 30 min before the lesion ameliorated the subsequent metabolic cortical depression seen in untreated animals. PZ given for 3 days starting before the lesion (3 mg/kg/day) was also effective in normalizing LCGU in areas where it was depressed by lesioning, despite the fact that this regimen induced significant global decrease in LCGU in normal animals. Once cortical metabolic depression had developed 3 days after the lesion, it could not be modified by PZ. YOH was less effective than PZ and was so only when given for 3 days (22.5 mg/kg/day in three divided doses). PZ (3 mg/kg/day in three divided doses) slightly but significantly decreased the accumulation of the serotonin (5-HT) metabolite 5-hydroxyindoleacetic acid in the traumatized hemisphere. These results provide evidence that blockage of alpha 1-adrenergic receptors prevents the development of cortical dysfunction associated with brain trauma. This implies that the noradrenergic system plays a role in the functional consequences of injury and that this effect is, at least in part, mediated by alpha 1-adrenergic receptors. Furthermore, alpha 1-adrenergic receptor blockage appears to modulate cortical turnover of 5-HT, previously also implicated in functional consequences of brain injury. The data are compatible with inhibitory effects of NE in the cortex and suggest a potential of alpha 1-adrenergic blockage in development of novel therapeutic approaches to brain injury.

The effect of pentobarbital and isoflurane on glucose metabolism in thermally injured rat brain.

The effect of pentobarbital and isoflurane on cerebral glucose metabolism (CMRglc) was studied in thermally injured rat brain using quantitative autoradiography. In awake lesioned animals, CMRglc in cortical regions ipsilateral to the injury was reduced to 50% of normal while little if any decrease was observed in contralateral cortical regions and subcortical regions bilaterally. Treatment of lesioned animals with pentobarbital or isoflurane further reduced CMRglc, but more in the hemisphere contralateral to the injury than on the injured side. Thus, the side-to-side difference in cortical CMRglc present in the awake lesioned animals was abolished by the anesthetics. The results support the hypothesis that CMRglc depression associated with a focal cold injury is functional in nature. Reduction of metabolism by anesthetics in functionally depressed brain is limited by the decrease in CMRglc associated with the injury.

Neurochemical approaches to the amelioration of brain injury.

The studies reported here represent a continuing search for mechanisms which may play a role in neurological disturbances resulting from brain injury. In particular, they are part of an effort to elucidate the involvement of both the serotonergic and noradrenergic neurotransmitter systems in the wide-spread decrease in cortical glucose utilization, interpreted as reflecting a functional depression, associated with a focal cortical lesion in the rat. Quinolinic acid, an endogenous metabolite of L-tryptophan, a neurotoxin and an N-methyl-D-aspartate (NMDA) receptor agonist was found to accumulate in cortical areas of a traumatized rat hemisphere in parallel with a previously demonstrated increase of 5-hydroxyindoleacetic acid. Ketanserin (20 mg/kg/day), a 5-HT2 receptor blocker ameliorated the depression of glucose utilization in traumatized brain while MK-801 (3 mg/kg, before and after lesion), an NMDA receptor blocker, had no effect. Alpha 1-adrenergic receptors, quantitated in vivo with [125I]-HEAT (iodo-2-[beta-(4-hydroxyphenyl)-ethyl-aminomethyl]tetralone), were found to be elevated in cortical areas of the lesioned hemisphere, but not in other structures.

Involvement of indoleamines in functional disturbances after brain injury.

1. Focal cortical freezing lesions in rats caused a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity (Pappius 1981). Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere (Pappius and Dadoun 1987). To find if these changes in the serotonergic system are of functional importance and mediate the observed changes in LCGU, the effects of inhibition of 5-HT synthesis with p-chlorophenylalanine (PCPA) on cerebral metabolism and indoleamine content in injured brain were studied (Pappius et al. 1988). PCPA decreased 5-HT levels in the cortical and raphe areas of both intact and injured brain in a dose dependent manner. At doses of PCPA ineffective on LCGU (50 and 100 mg/kg) brain trauma still resulted in increased 5-HT metabolism. PCPA at doses which selectively ameliorated the depression of cortical LCGU in the lesioned hemisphere (200 and 300 mg/kg) completely prevented changes in 5-HT and 5-hydroxyindoleacetic acid seen following traumatization in untreated animals. These results provide evidence that decreased LCGU in lesioned brain is due to an activation of the serotonergic system. The data are thus in agreement with a postulated inhibitory role of serotonin in the cerebral cortex, and its involvement in functional alterations associated with injury.

Significance of biogenic amines in functional disturbances resulting from brain injury.

Focal cortical freezing lesions in rats caused a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity (Pappius, 1981). Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere (Pappius and Dadoun, 1987). In contrast, norepinephrine (NE) was decreased bilaterally, while levels of dopamine and its metabolites were not affected (Pappius and Dadoun, 1986). To determine if the changes in these neurotransmitters are of functional importance and mediate the observed changes in LCGU, the effects of inhibition of 5-HT synthesis with p-chlorophenylalanine (PCPA) and alpha 1-adrenergic blockage with prazosin (PZ) on cerebral metabolism and biogenic amine content in injured brain were studied. At doses of PCPA ineffective on LCGU (50 and 100 mg/kg) brain trauma still resulted in increased 5-HT metabolism. PCPA at doses which selectively ameliorated the depression of cortical LCGU in the lesioned hemisphere (200 and 300 mg/kg) completely prevented changes in 5-HT and 5-hydroxyindoleacetic acid seen following traumatization in untreated animals. These results provide evidence that decreased LCGU in lesioned brain is due to an activation of the serotonergic system. Prazosin (1 mg/kg) given 30 min before the lesion significantly increased cortical glucose utilization in the injured hemisphere and was even more effective when the treatment was continued for 3 days. Prazosin did not modify changes in cortical biogenic amines seen in untreated animals. The data are in agreement with a postulated inhibitory role of serotonin and norepinephrine in the cerebral cortex and implicate both neurotransmitters in functional alterations associated with injury.

The effect of p-chlorophenylalanine on cerebral metabolism and biogenic amine content of traumatized brain.

It was shown previously that focal cortical freezing lesions in rats cause widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere. This was interpreted as reflecting a depression of cortical activity. It was then demonstrated that cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere of a focally injured brain. To find out if the changes in the serotonergic system are of functional importance and mediate the observed changes in LCGU, the effects of the inhibition of 5-HT synthesis with p-chlorophenylalanine (PCPA) on cerebral metabolism and biogenic amine content in injured brain were studied. PCPA in doses up to 300 mg/kg had little, if any, effect on LCGU in intact brain and in doses up to 100 mg/kg did not modify the depressed LCGU in injured brain. In doses of 200 and 300 mg/kg, PCPA selectively increased cortical glucose utilization in the lesioned hemisphere where it was depressed following injury. PCPA decreased 5-HT levels in the cortical and raphe areas of both intact and injured brain in a dose-dependent manner. However, at doses of PCPA ineffective on LCGU (50 and 100 mg/kg), traumatization still resulted in increased 5-HT metabolism. Doses of PCPA that ameliorated the depression of LCGU in injured brain completely prevented increases in both 5-HT and its metabolite 5-hydroxyindoleacetic acid seen following traumatization in untreated animals. These results provide evidence that decreased LCGU in lesioned brain is due to an activation of the serotonergic system by traumatization. The data are in agreement with the postulated inhibitory role of serotonin in the cortex and its involvement in functional alterations associated with injury. They suggest that blockage of this neurotransmitter system may have a potential in the development of novel therapeutic approaches to brain injury.

Effects of injury on the indoleamines in cerebral cortex.

It was shown previously that focal cortical freezing lesions in rats cause widespread depression of local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere. This was interpreted as reflecting functional depression. The underlying mechanisms were postulated to involve alterations of biogenic amine systems. Accordingly, levels of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and its precursor tryptophan were determined by an HPLC method with electrochemical detection in frontoparietal cortical areas of both hemispheres at 4 h and 1, 3, 6, 8, and 10 days after a unilateral cortical freezing lesion. The 5-HT content was significantly lower than normal in the lesioned hemisphere only at 24 h, whereas the 5-HIAA level peaked at 24 h but was significantly elevated above normal values between 4 h and 6 days after lesioning. No changes were noted in 5-HT and 5-HIAA contents in the hemisphere contralateral to the lesion. These results indicate that cortical 5-HT metabolism is increased throughout the lesioned hemisphere of a focally injured brain. The increase in tryptophan content of the lesioned brain appeared to have a time course more closely related to previously demonstrated changes in cortical LCGU than to the increase in 5-HIAA content.

Correlation between behavioral status and cerebral glucose utilization in rats following freezing lesion.

Standard small, superficial freezing lesions placed along the anterior-posterior plane of the left cortex produced behavioral changes in rats. One to 3 days following the lesion, rats showed asymmetries in somatosensory responsiveness, decreases in running wheel activity and difficulty with limb coordination. No changes in spontaneous circling were seen. At the completion of the behavioral testing on day 3 the [14C]2-deoxyglucose method confirmed the presence of widespread depression in local cerebral glucose utilization with cortical areas ipsilateral to the lesion being most affected. At this time the degree of the somatosensory deficit was significantly correlated with the extent of the depression of glucose utilization in the cortical areas of the lesioned hemisphere. At 6 days following the lesion only deficits in limb coordination remained, while local cerebral glucose utilization had returned to within normal limits. It is concluded that the demonstrated behavioral changes were a manifestation of widespread functional depression, as reflected by decreased cortical glucose utilization throughout the lesioned hemisphere.

Effects of two dihydropyridine calcium channel blockers on cerebral metabolism and blood flow in traumatized rat brain.

The effect of two dihydropyridine calcium (Ca) channel blocking drugs on cerebral glucose metabolism (LCGU), blood flow (LCBF), and blood flow-metabolism coupling were studied in thermally injured rat brain using quantitative radioautographic techniques. No reversal of the previously noted LCGU depression caused by the freezing lesion (Pappius, 1981) was detected following treatment with either PY-108-068 (PY) or nimodipine (NIM). These results therefore provided no support for the role of Ca in the mechanism of functional disturbances induced by cold injury (Pappius and Wolfe, 1983b), though they do not rule out its involvement. Treatment with PY, but not NIM, reestablished the normal LCBF-LCGU relationship in cortical areas, which has been shown to be disturbed by the freezing lesion and in subcortical and brainstem structures, in which the alteration caused by the injury was not as pronounced. The results suggest that the mechanism that apparently uncouples LCBF from LCGU in injured brain is altered in the presence of PY. However, since NIM did not have the same effect on LCBF, it is not clear whether the effects of PY relate to blockade of Ca channels or some other effect of PY.