Effects of d- and l-amphetamine on local cerebral glucose utilization in the conscious rat

Local cerebral glucose consumption in the rat. II. Effects of unilateral substantia nigra stimulation in conscious and in halothane-anesthetized animals

The energy metabolism of 74 anatomically discrete central nervous structures was investigated by means of the autoradiographic 2-deoxy-D-(1-14C)glucose method (14C-DG) in conscious awake, as well as in halothane-anesthetized rats, following unilateral substantia nigra (SN) electrical stimulation. All the basal ganglia structures displayed bilateral metabolic activation in conscious animals, with only the contralateral subthalamic nucleus being unaffected. In anesthetized rats only the SN reticulata, globus pallidus, and subthalamic nucleus were affected ipsilaterally whereas anesthesia masked the effects of SN stimulation in SN compacta and striatum ipsilaterally, as well as within all the above structures contralaterally. The entopeduncular nucleus was bilaterally activated no matter the state of consciousness. Unilateral SN stimulation also increased glucose utilization within several thalamic regions (ventromedial, ventrolateral, ventroanterior, intralaminar, ventrobasal, and mediodorsal nuclei), the habenular complex, a few mesencephalic, brainstem (locus coeruleus and dorsal raphe) and cerebellar structures, mostly bilaterally and independently of the state of consciousness. Some of the factors suggested to be responsible for the masking effects of halothane-anesthesia on the metabolic activations elicited by unilateral SN stimulation are the following: (1) absence of movements in anesthetized rats, (2) halothane-induced depression of polysynaptic pathways mostly mediated through the thalamus, and (3) the stimulatory effect of halothane-anesthesia itself on metabolic activity in both parts of the SN.

Increased local cerebral glucose utilization in the basal ganglia of the rolling mouse Nagoya

Rolling mouse Nagoya (rolling), an experimental mutant mouse, is characterized by a marked incoordination of the hind limbs and disturbance of gait. These motor disturbances have been attributed to cerebellar dysfunction, and rolling, therefore, has been regarded as an animal model of hereditary cerebellar ataxia. However, definite evidence for this possibility has not yet been provided. In the present study, local cerebral glucose utilization (LCGU) was observed by means of the [14C]deoxyglucose method in rolling (rol/rol), as well as in behaviorally normal heterozygotes (+/rol) and normal controls (+/+), in order to study functional activity of the brain in these mice. A definite increase in LCGU was found in the globus pallidus, entopeduncular nucleus, subthalamic nucleus, and substantia nigra of rolling, bilaterally. A minimal decrease in LCGU was also found in the vermis of the cerebellum. These findings reflect the markedly hyperactive state of the basal ganglia and the minimally hypoactive state in the vermis of the cerebellum in rolling. It is concluded that the dysfunction in the basal ganglia is the major cause of the motor disturbances of rolling, and that rolling may be regarded as an animal model of extrapyramidal motor disturbance.

Effects of reinforcement-blocking doses of pimozide on neural systems driven by rewarding stimulation of the MFB: a 14C-2-deoxyglucose analysis

An analysis by means of 14C-2-deoxyglucose autoradiography of the neural systems unilaterally activated by the reinforcing stimulation used in the two accompanying papers revealed strong and reliable effects in the nucleus of the diagonal band of Broca, in the medial forebrain bundle (MFB) and/or the fornix throughout the diencephalon, and in the part of the anterior ventral tegmentum where the dopaminergic projection to the lateral habenula originates. The terminal fields of the dopaminergic forebrain projections were not affected, but there was bilateral suppression of lateral habenular activity. A second experiment found that the same systems are still activated by (automatically administered) reinforcing stimulation in rats treated with reinforcement blocking doses of pimozide. The only clear effect of pimozide was to reverse the bilateral suppressive effect of the stimulation on lateral habenular activity. Animals treated with pimozide show greatly elevated activity in the lateral habenula, whether or not they receive reinforcing stimulation. The results suggest that pimozide's effect on reinforcement is mediated by the circuitry interconnecting the lateral habenula with the nucleus of the diagonal band of Broca and/or the anterior ventral tegmentum.

Effects of the putative GABAergic agonists, muscimol and THIP, upon local cerebral glucose utilisation

The dose-dependent effects of two putative gamma-aminobutyric acid (GABA)-ergic agonists, muscimol and 4,5,6,7-tetrahydroisoxazolo(4,5-e)-pyridin-3-ol (THIP), upon local cerebral glucose utilisation in 60 discrete regions of the CNS have been examined in conscious rats using the [14C]2-deoxyglucose quantitative autoradiographic technique. The intravenous administration of muscimol (0.15-5 mg/kg) and THIP (1-10 mg/kg) resulted in a heterogeneous pattern of significantly reduced glucose utilisation throughout the CNS. The regional hierarchy of changes in glucose utilisation was similar for both muscimol and THIP in all regions (with the exception of the superior colliculus), with muscimol being approximately six times more potent in all regions investigated. The regions in which glucose utilisation was extremely sensitive to change, displaying reductions of approximately 40% following muscimol (1.5 mg/kg) or THIP (10 mg/kg) administration, included all layers of the neocortex (frontal, sensory motor, posterior parietal, primary auditory and visual cortices), the lateral portion of the caudate nucleus, and some thalamic nuclei (lateral geniculate body, mediodorsal and ventrolateral nuclei). Regions displaying more modest reductions in glucose utilisation, approximately 20% following muscimol (1.5 mg/kg) and THIP (10 mg/kg) administration, included most extrapyramidal regions (substantia nigra, pars compacta and reticulata, globus pallidus, subthalamic nucleus, medial portion of the caudate nucleus), a number of cortical and subcortical limbic areas (cingulate and olfactory cortices, hippocampus, nucleus accumbens, anterior thalamus), and medial raphe nucleus. In contrast, in a large number of regions (including cerebellum and related nuclei such as the inferior olivary, red and vestibular nuclei, white matter, pontine reticular formation, hypothalamus, lateral habenula and amygdala), there were only minimal (approximately 10%) reductions in glucose utilisation following muscimol (1.5 mg/kg) and THIP (10 mg/kg) administration. In no region of the CNS was a significant increase in glucose utilisation observed with any concentration of either muscimol or THIP. The regional distribution of alterations in glucose utilisation following muscimol and THIP administration, which does not correspond to the known topography of GABAergic neurones and receptors, provides a comprehensive description of the functional alterations, as reflected in rates of glucose utilisation, that occur in conscious rats after systemic administration of these two putative GABAergic agonists.

Distribution of effects of haloperidol on energy metabolism in the rat brain

The effects of the putative dopaminergic antagonist, haloperidol (0.01-10 mg/kg, i.v.), on cerebral glucose utilization in 43 anatomically discrete regions of the rat brain have been examined by the quantitative autoradiographic 2-deoxyglucose technique. Dose-dependent reductions in glucose utilization were observed in 10 regions of the CNS (e.g. hippocampus, ventral thalamus and almost the entire neocortex, with the notable exception of anterior cingulate cortex). Two regions of the CNS (nucleus accumbens and pars compacta of the substantia nigra) displayed dose-related increases in glucose utilization following haloperidol administration. In addition to these specific alterations, the largest doses of haloperidol produced widespread, moderate (about 25%) reductions in glucose utilization throughout the CNS. The prior administration of haloperidol (0.1 mg/kg) prevented the effects on glucose utilization of the administration of apomorphine (1.5 mg/kg) in all regions of the CNS examined. The distribution of alterations in glucose utilization following haloperidol administration are considered in relation to the overall functional consequences of dopaminergic receptor blockade.

The distribution of alterations in energy metabolism in the rat brain produced by apomorphine

The effects of the putative dopaminergic agonist, apomorphine (0.15-5 mg/kg, i.v.), on glucose utilization in 43 anatomically discrete regions of the rat brain have been examined by the quantitative autoradiographic 2-deoxyglucose technique. Apomorphine failed to alter the rates of glucose utilization in 25 of these regions (for example, primary auditory areas, regions of white matter, hippocampal areas, nucleus accumbens and caudal regions of the neocortex). Dose-dependent alterations in glucose utilization were observed following apomorphine administration in a number of regions known to contain dopaminergic receptors (viz: caudate nucleus, substantia nigra, amygdala, subthalamic nucleus and anterior cingulate cortex). Moreover, dose-dependent alterations in glucose utilization were produced by apomorphine in a number of regions thought to contain few specific dopaminergic receptors (e.g., cerebellar hemisphere and vermis, lamina VI of rostral neocortical areas, and ventral nucleus of the thalamus). The distribution of alterations in glucose utilization following apomorphine administration are considered to reflect the functional involvement of the region in the overall response to apomorphine, and not simply the topography of dopaminergic receptor mechanisms.

No effect of hyperketonemia on local cerebral glucose utilization in conscious rats

Local cerebral glucose utilization was measured by the [14C]2-deoxy-D-glucose method in conscious control and hyperketonemic rats. Hyperketonemia was induced by 3 days of starvation or by infusion of 3-hydroxybutyrate in fed rats. These treatments produced combined blood ketone body concentrations (acetoacetate + 3-hydroxybutyrate) of from 1.2 to 2.4 mM. Neither treatment significantly affected glucose utilization in any of the 15 brain regions studied. These observations indicate that hyperketonemia in resting, conscious rats does not interfere with brain uptake and phosphorylation of glucose.

Th central noradrenergic system in the rat: metabolic mapping with alpha-adrenergic blocking agents

Rates of cerebral glucose utilization were measured by means of the autoradiographic 2-deoxy-D-[14C]glucose technique in 73 normal, awake rats treated with different doses of the alpha-adrenergic blockers, phenoxybenzamine, phentolamine and yohimbine. Three types of responses were elicited by the administration of these drugs. The predominant effect observed after administration of all alpha-blockers was a widespread depression of glucose utilization, particularly within the neocortex. The effect was most pronounced with phenoxybenzamine. In a few structures (locus coeruleus, interstitial nucleus of the stria terminalis, medial forebrain bundle, periventricular nucleus and some medullary and hypothalamic nuclei associated with the regulation of blood pressure) marked increases in glucose utilization were observed. Administration of phentolamine resulted in increased glucose utilization in all the central components of the auditory system (cochlear n., superior olivary n., n. lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). Phenoxybenzamine and yohimbine tended to decrease glucose utilization in the auditory system. Alternating columns with higher and lower rates of local glucose consumption were observed in most of the neocortical areas and in the cerebellar vermis. The significance of these columns is not clear.

Simultaneous measurement of blood flow and glucose metabolism by autoradiographic techniques

A double tracer autoradiographic technique using 131I-iodo-antipyrine and 14C-deoxyglucose is presented for the simultaneous measurement of blood flow and cerebral glucose utilization in the same animal. 131I is a gamma emitting isotope with a half life of 8.06 days and can be detected with adequate resolution on standard autoradiographic films. Autoradiograms are made before and after decay of 131I; the time interval between the 2 exposures and the concentration of the 2 tracers is adjusted to avoid significant cross-contamination. In this way, 2 film exposures are obtained which can be processed quantitatively like single tracer autoradiograms. The validity of the method for the investigation of local coupling of flow and metabolism was tested under various physiological and pathophysiological conditions. Coupling was tight in barbiturate-anesthetized healthy animals, but not under halothane anesthesia where uncoupling occurred in various subcortical structures. Focal seizures induced by topical application of penicillin on the cortical surface led to a coupled increase of metabolism and flow in thalamic relay nuclei but not at the site of penicillin administration where increased glucose utilization was not accompanied by similar increase in blood flow. Both coupled and uncoupled increases in local glucose utilization were observed in spreading depression and in circumscribed areas of experimental brain tumors. The results obtained demonstrate that double tracer autoradiography allows allows the very precise local assessment of cerebral blood flow and glucose utilization, and, therefore, is particularly suited to the study of regional coupling processes under various experimental conditions.

The effects of chloral hydrate anesthesia on the metabolic response in the substantia nigra to apomorphine

The effects of apomorphine (1 mg/kg) upon glucose utilization in the substantia nigra (pars compacta) have been examined with 2-deoxyglucose autoradiography in conscious rats and rats anesthetized with chloral hydrate. In conscious rats, apomorphine increased glucose use by 23%, whereas in the anesthetized rats, apomorphine decreased glucose use by 24%. These divergent responses to apomorphine highlight the difficulties associated with the use of chloral hydrate anesthesia in the study of nigro-striatal systems.

Heterogeneous depression of glucose utilization in the caudate nucleus by GABA agonists

Local cerebral glucose utilization in the rat caudate nucleus has been examined following the intravenous administration of the GABA agonists muscimol and THIP. Although glucose utilization was reduced throughout the striatum following GABA agonists, the magnitude of the reductions in the lateral portion of the nucleus were markedly greater than in other portions of the caudate nucleus. This medial--lateral heterogeneity in response to GABA agonists contrasts with the known rostral--caudal heterogeneity in the distribution of biochemical markers for GABA.

On the evolution and growth of lateralization

This is a welcome attempt to seek common biological principles underlying laterality in animals and humans. I do not think it is wholly convincing, but this is partly because many of the results from nonhuman species are not yet firmly established or understood. I suspect that the author's characterization of lateralization, with the left hemisphere supposedly specialized for communicative functions and the right for spatial and affective functions, will require modification. For instance, it now seems fairly clear that the left hemisphere in humans plays a general role in the production and perception of sequences not restricted to communicative acts (Craig 1980; Kimura 1979), and indeed some of the examples of left-hemispheric specialization listed in Table 2 are not obviously communicative. Even so, there are some fairly striking parallels between humans and nonhumans with respect to the pattern of lateralization, and one suspects that common principles are operating. At the same time, in the enthusiastic search for functional asymmetries, we should not overlook the striking degree of bilateral symmetry that characterizes the brains of all animals, including humans.

Cerebral predominance in the monkey?

The issues raised by Dr. Denenberg are complex, not least because the apparent communalities of hemispheric specialization among birds, rodents, monkeys, and human beings are also associated with negative instances (e.g., for parrots, Nottebohm 1976; for Macaco, other than fuscata, Petersen et al. 1978). To extend the available evidence I would like to refer to the preliminary findings of Garcha et al. (1980) on the monkey.

Hemispheric laterality and an evolutionary perspective

Denenberg rightly stresses the importance of studying ethologically meaningful species-specific behavior in animals, and makes the interesting distinction between lateralization at an individual and at a population level. However, in the case of man, I believe Denenberg is wrong in arguing that lateralization in the individual increases with maturation. The overall evidence nowadays tends very much to the contrary. Moreover, with respect to a population, why should it become lateralized? If there is indeed an advantage for the individual in hemispheric specialization, why should the direction of such specialization be so consistent across a majority of individuals, whether human or, as Denenberg points out, other members of the phylum? Is there an evolutionary advantage in most animals' sharing the same direction, or is it a necessary consequence of some other preexisting, more fundamental anatomical, biochemical, or physical property of the organism and its constituents? If the former, why are not all members of the species, rather than just a majority, lateralized in the same direction? (Or, to put it another way, what is the evolutionary advantage to the species or individual of dimorphism, of retaining a minority who polarize in the opposite direction?) If the latter - i.e., if lateralization is a necessary consequence of some prior state - then there should not be any dimorphism, exceptions, or minority members, unless they are somehow disadvantaged in consequence. Indeed, there is some evidence of a cognitive deficit in sinistrals, though it is disputed (see Bradshaw 1980 for review), and others have even suggested that the species as a whole may benefit in some way from such an uneven dimorphism (Levy 1974), but what evidence is there for such propositions with respect to rats, apes, monkeys, or chicks? This is an issue that should be addressed in any general model that includes laterality in animals. [See Corhallis & Morgan: “On the Biological Basis of Human Laterality” BBS 1(2) 1978.]

Dendritic release of dopamine in the substantia nigra

Dopamine can be released in the substantia nigra for the dendrites of nigrostriatal dopaminergic neurones, to be involved there in the self-regulation of the dopaminergic cells, to control the release of neurotransmitters from nigral afferent fibres and to influence the activity of nigral non-dopaminergic cells.

Effects of naftidrofuryl on local cerebral glucose utilization in the rat

The effects of naftidrofuryl on local cerebral glucose utilization have been examined in 21 lightly restrained, conscious rats by means of the quantitative autoradiographic 2-deoxyglucose technique. Naftidrofuryl (15, 30, and 45 mg/kg, i.p.) did not significantly alter the rate of glucose utilization in any of the 29 gray matter or 4 white matter areas that were examined.

Effect of thyrotropin-releasing hormone (TRH) on local cerebral glucose utilization, by the autoradiographic 2-deoxy[14C]glucose method, in conscious and pentobarbitalized rats

Effects of TRH and pentobarbital alone, and in combination, on local cerebral glucose utilization of rats were studied by the autoradiographic 2-deoxy[14C]glucose method. TRH (5 mg/kg i.v.) reduced the rate of cerebral glucose utilization slightly in the whole brain. Locally, significant depression was observed in the following structures: frontal and visual cortices, hippocampus Ammon's horn and dentate gyrus, medial and lateral geniculate bodies, nucleus accumbens, caudate-putamen, substantia nigra, pontine gray matter, superior colliculus, superior olivary nucleus, vestibular nucleus, lateral lemniscus and cerebellar cortex. Pentobarbital (30 mg/kg i.v.) produced a marked and diffuse reduction in the rate of glucose utilization throughout the brain. TRH given 15 min after the administration of pentobarbital markedly shortened the pentobarbital sleeping time and caused some reversal of the depression in local cerebral glucose utilization produced by pentobarbital. These effects were almost completely abolished by pretreatment with intracerebroventricular injection of atropine methyl bromide (20 microgram/rat). These results indicate that although TRH acts to cause a reduction in the rate of cerebral glucose utilization, it reverses the depression induced by pentobarbital, via a cholinergic mechanism, in a number of structures, some of which are related to monoaminergic systems and the reticulo-thalamo-cortical activating system.

The effect of unilateral basilar papilla removal upon nuclei laminaris and magnocellularis of the chick examined with [3H]2-deoxy-D-glucose autoradiography

The effect of unilateral basilar papilla removal on glucose uptake in the 2nd and 3rd order auditory nuclei in the chick's brain stem, nucleus magnocellularis and nucleus laminaris, respectively, was examined with [3H]2-deoxy-D-glucose (2-DG) autoradiography. The tissue was processed according to a thaw-mount technique, and the number of grains in the resulting autoradiographs was counted to assess changes in glucose uptake. It was observed that there is a greater density of grains over the neuropil regions of nucleus laminaris which receive input from the normal ear than over the corresponding regions which receive input from the operated ear. Similarly, differences in grain density are found between the normally innervated and deafferented magnocellular nuclei although these differences are not as great as those in nucleus laminaris. Differences in grain density were also apparent between the glial/fiber regions which bound the neuropil areas of nucleus laminaris; there is a greater density of grains overlying those glial/fiber regions through which fibers receiving input from the normal ear course than over those regions through which fibers which normally carry input from the operated ear travel. It is likely that this difference mainly reflects glucose uptake in the fibers although a possible contribution of glial tissue cannot be excluded. All these effects of basilar papilla removal are seen with survival times as short as 70 min and thus likely reflect the reduction of neural activity rather than the degeneration of pre- or postsynaptic elements. Finally, the same pattern of results as described above was found when using the more common [14C]2-DG procedure or when using [3H]2-DG but processing the tissue using the freeze-dried technique. The present results thus show the neuropil regions of nucleus laminaris and the adjacent glial/fiber areas to be areas of high glucose utilization. Unilateral basilar papilla removal results in the removal of an excitatory input to these regions, and this results in a reduction of glucose utilization that is specific to those neuropil regions and glial/fiber areas that receive input from the operated ear. These findings are contrasted with another study in which removal of a major excitatory input to the dentate gyrus of the rat results in a reduced glucose utilization which is not specific to the deafferented region and which largely reflects post- rather than presynatic events.

Intraperitoneal administration and other modifications of the 2-deoxy-D-glucose technique

Experiments were conducted to determine the optimal conditions necessary for implementing modifications of the 2-deoxyglucose (2-DDG) technique. Substitution of tritium-labeled 2-DDG with subsequent microdissection of selected brain regions and liquid scintillation counting produced results that were highly correlated with both [14C]radioautograms and glucose utilization values as obtained by Sokoloff et al. The route of administration of isotope was also varied. Whole brain uptake at maximal levels of incorporation was the same for both intravenously and intraperitoneally injected animals. Radioautograms from i.p. and i.v. injected animals were indistinguishable. Densitometric analyses of the i.p. radioautograms were highly correlated with glucose utilization values. Thus, relative indices of functional activity may be obtained when experimental circumstances preclude arteriovenous cannulations and restraint. The use of naive, unrestrained animals, therefore, makes the 2-DDG technique applicable to a broader range of studies.

Regional cerebral glucose utilization measured with the 2--[ 14C] deoxyglucose technique: its use in mapping functional activity in the nervous system

The results of studies with the [ 14C] deoxyglucose technique unequivocally establish that functional activity in specific components of the central nervous system is, as in other tissues, closely coupled to the local rate of energy metabolism. Stimulation of functional activity increases the local rate of glucose utilization; reduced functional activity depresses it. These changes are so profound that they can be visualized directly in autoradiographic representations of local tissue concentrations of [ 14C] deoxyglucose-6-phosphate. Indeed, the existence of such evoked metabolic responses to experimentally induced alterations in local functional activity, together with the ability to visualize them by the [ 14C] deoxyglucose method, has become the basis of a potent technique for the mapping of functional pathways in the central nervous system (Kennedy et al., 1975, 1976; Plum et al., 1976).

Influence of dopaminergic systems on the lateral habenular nucleus of the rat

The alterations in glucose utilization in the lateral habenular nucleus following the systemic administration of a putative dopaminergic agonist and antagonist have been examined in 48 rats by means of the autoradiographic 2-deoxyglucose technique. The administration of apomorphine (0.15--5 mg/kg) resulted in significant dose-dependent reductions (by 25 +/- 5% following 0.5 mg/kg) in glucose utilization in the lateral habenula. Haloperidol administration (0.01--10 mg/kg) was associated with increased (by 46 +/- 17% with 0.1 mg/kg) glucose utilization in the lateral habenula. The effects of apomorphine upon metabolic activity in the lateral habenula can be prevented by the prior administration of haloperidol (0.1 mg/kg). These observations provide evidence that metabolic activity in the lateral habenula, a nucleus occupying a strategic position between the forebrain and the mesencephalon, may be regulated by the activity in dopaminergic systems.

Effects of substantia nigra lesions on forebrain 2-deoxyglucose retention in the rat

A method was developed for the measurement of regional 2-deoxyglucose (2-DG) retention in rat brain by injecting tracer quantities of tritated 2-DG intravenously, dissecting out individual brain regions, making extracts of the tissue, and counting aliquots of the extracts. This technique permits the separation of unreacted 2-DG from 2-deoxyglucose-6-phosphate (2-DGP) by ion exchange chromatography as well as the performance of other biochemical measurements on the extracts. Using this method, the effect of unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra on 2-DG retention and 2-DGP formation by the striatum and the cerebral cortex was investigated. Animals were studied both 3 days and 2--4 weeks after lesioning. The location and efficacy of the lesions were verified histologically, behaviorally (by observing rotational behavior), and biochemically (by assay of striatal dopamine concentration or tyrosine hydroxylase activity). The lesions induced a mean asymmetry of less than 10% in 2-DG retention and in 2-DGP formation in striatum and cerebral cortex. This result was verified by [14C]2-DG autoradiography. Systemic administration of amphetamine (5 mg/kg) or apomorphine HBr (1.5 mg/kg) elicited rotational behavior, but did not induce a marked asymmetry of 2-DG retention in the regions studied. It is concluded that unilateral lesions of the nigrostriatal dopaminergic pathway have, at most, a modest effect on 2-DG retention by forebrain structures. We also conclude that vehicle injections may produce morphological and chemical evidence of brain injury, including small but reproducible changes in deoxyglucose retention.