Storage and release of endogenous and labelled GABA formed from [H]Glutamine and [C]Glucose in hippocampal slices: Effect of depolarization

To study the effect of depolarization on the synthesis, storage and release of GABA, hippocampal slices were incubated in 0.25 mM [³H]glutamine and 2.5 mM [¹⁴C]glucose in the presence of 3 or 50 mM K⁺. Total and labelled glutamine, glutamate and GABA contents were measured by high-performance liquid chromatography. Depolarization in the presence of Ca²⁺ led to a two-fold increase of labelled glutamate and a 3-fold increase of labelled GABA content originating from both labelled precursors. In the absence of Ca²⁺ and in the presence of 10 mM Mg²⁺, depolarization failed to increase labelled glutamate content and labelled GABA formation was increased by only 30%. Following superfusion with unlabelled 0.25 mM glutamine and 2.5 mM glucose a second depolarization with 50 mM K⁺ released twice as much labelled GABA from slices that had been incubated in the presence of 50 mM K⁺, than from those incubated in 3 mM K⁺. This difference remained unchanged in slices that were superfused with 1 mM aminooxyacetic acid, an inhibitor of GABA synthesis. The contribution of labelled GABA, especially of GABA derived from [³H]glutamine, to released GABA was significantly higher than to GABA stored in the slices. Results suggest that depolarization in the presence of Ca²⁺ results in increased glutamate and GABA synthesis from both glutamine and glucose and that part of GABA released by high K⁺ originates from preformed GABA stores.     

Short and long-term changes in cerebral [14C]-2-deoxyglucose uptake in the MPTP-treated marmoset: relationship to locomotor activity

Summary The short-term (0.7 ± 0.1 months post-MPTP) and long-term effects (36.7 ± 4.4 months) of MPTP treatment on motor behaviour and [¹⁴C]-2DG uptake were investigated in the common marmoset. The subcutaneous administration of MPTP greatly reduced locomotor activity (–94% with respect to controls) and induced motor disability in the short-term MPTP-treated marmoset group. In the long-term MPTP group, MPTP treatment did not significantly affect locomotor activity (–27% with respect to controls) and there was partial recovery of motor disability.In the short-term MPTP group, there were increases in [¹⁴C]-2DG uptake in the GP1 (+31 to +37%), SNc (+34 to +42%), VTA (+35%), LC (+23%), PPN (+19%) and in the VA (+19%), VL (+20%) and AM (+17%) thalamic nuclei. [¹⁴C]-2DG uptake was decreased in the STN (–15%). In the long-term MPTP group, [¹⁴C]-2DG uptake was increased in the GP1 (+18%), SNc (+27%), VTA (+25%), PPN (+19%), ventral caudate nucleus (+18 to +23%), NAc (+22%), F.Ctx (+18%) and in the VA (+34%), VL (+28%), AV (+33%) and AM (+24%) thalamic nuclei. [¹⁴C]-2DG uptake was unchanged in the STN.The increase in metabolic activity of the surviving DA neurones and/or the reactive gliosis may account for the initial increase in [¹⁴C]-2DG uptake in the SNc and VTA. On the other hand, in the long-term MPTP-treated animals the increase in [¹⁴C]-2DG uptake in the SNc (though less than in the short-term MPTP group), ventral caudate and NAc may reflect the regenerative changes in the dopaminergic system in these areas. Despite the behavioural recovery, [¹⁴C]-2DG uptake remained elevated in the target areas for medial paludal output (the thalamic nuclei and PPN). However, the attenuation of the changes in [¹⁴C]-2DG uptake in the GP1 and STN of longterm MPTP-treated marmosets suggest that the striato-GPl and GP1-STN outputs closely reflect motor function in this primate model of Parkinson's disease.Anatomical abbreviations AM anteromedial thalamus - AV anteroventral thalamus - CeM centromedian thalamus - d dorsal - F.Ctx frontal cortex - GP1 lateral segment of globus pallidus - GPm medial segment of globus pallidus - HBl lateral habenular - HBm medial habenular - IC inferior colliculus - l lateral - LC locus coeruleus - m medial - MD mediodorsal thalamus - NAc nucleus accumbens - OT olfactory tubercle - PPN pedunculopontine nucleus - Rt reticular thalamus - SNc substantia nigra pars compacta - SNr substantia nigra pars reticulata - STN subthalamic nucleus - v ventral - VA ventral anterior thalamus - VL ventral lateral thalamus - VTA ventral tegmental area Chemical abbreviations DA dopamine - GABA gamma aminobutyric acid - MPP⁺ 1-methyl-4-phenylpyridinium ion - MPTP 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine - [¹⁴C]-2DG [¹⁴C]-2-deoxyglucose     

[C]2-Deoxyglucose demonstration of the organization of ocular dominance in areas 17 and 18 of the normal cat

The purpose of this study was to demonstrate the spatial organization of ocular dominance in the visual cortex of the cat. We administered [14C]2-deoxyglucose ([14C]2-DG) to 4 alert, monocularly stimulated cats; one eye had previously been removed from 3 of these cats, and the other cat had received a uniocular injection of tetrodotoxin (TTX). In areas 17 and 18, but not in area 19, we observed alternating regions of heavy and light label, which were clearest in layer IV. Near the representation of the area centralis, especially in the hemisphere ipsilateral to the stimulated eye, the labeled regions formed columns that extended from the pial surface to the white matter. In the representation of peripheral retina, especially in the hemisphere contralateral to the stimulated eye, the pattern was often (but not always) restricted to the middle layers. We conclude that this pattern of label reflects the organization of ocular dominance because: (1) we never observed this pattern in control cats in which both eyes were stimulated or neither eye was stimulated; (2) many characteristics of the pattern are consistent with physiological studies of ocular dominance, and (3) the width and spacing of the alternating label was consistent with the size of the patches of geniculocortical afferents representing the left and right eyes in layer IV of areas 17 and 18.     

The effect of auditory stimulus rate on [C]2-deoxyglucose uptake in rabbit inferior colliculus

The relationship between auditory stimulus rate and level of [¹⁴C]2-deoxyglucose (2-DG) uptake was examined using the 2-DG technique developed by Sokoloff³⁴ as an indication of glucose uptake and neural activity. Conscious restrained albino rabbits were given one monaural tone either once per second or once per minute for 45 min, or served as unstimulated controls. Autoradiographs of the inferior colliculi from these animals were compared densitometrically. It was found that the rabbits stimulated once per second had markedly elevated levels of 2-DG uptake compared to both other groups: the rabbits stimulated once per minute and to unstimulated control rabbits. In addition, the inferior colliculus autoradiographs of the rabbits stimulated with pure tones showed a distinctive banding pattern in central nucleus different from that seen in control rabbits.     

Imaging in vivo glutamate fluctuations with [11C]ABP688: a GLT-1 challenge with ceftriaxone

Molecular imaging offers unprecedented opportunities for investigating dynamic changes underlying neuropsychiatric conditions. Here, we evaluated whether [¹¹C]ABP688, a positron emission tomography (PET) ligand that binds to the allosteric site of the metabotropic glutamate receptor type 5 (mGluR5), is sensitive to glutamate fluctuations after a pharmacological challenge. For this, we used ceftriaxone (CEF) administration in rats, an activator of the GLT-1 transporter (EAAT2), which is known to decrease extracellular levels of glutamate. MicroPET [¹¹C]ABP688 dynamic acquisitions were conducted in rats after a venous injection of either saline (baseline) or CEF 200 mg/kg (challenge). Binding potentials (BP_ND) were obtained using the simplified reference tissue method. Between-condition statistical parametric maps indicating brain regions showing the highest CEF effects guided placement of microdialysis probes for subsequent assessment of extracellular levels of glutamate. The CEF administration increased [¹¹C]ABP688 BP_ND in the thalamic ventral anterior (VA) nucleus bilaterally. Subsequent microdialysis assessment revealed declines in extracellular glutamate concentrations in the VA. The present results support the concept that availability of mGluR5 allosteric binding sites is sensitive to extracellular concentrations of glutamate. This interesting property of mGluR5 allosteric binding sites has potential applications for assessing the role of glutamate in the pathogenesis of neuropsychiatric conditions.     

Stimulus-dependent labeling of cultured ganglionic cell with [C]2-deoxyglucose

We prepared cultures of dissociated cells from the ciliary (CG) and dorsal root ganglion (DRG) of 10–12-day-old chick embryos, and applied [¹⁴C]2-deoxyglucose ([¹⁴C]2-DG) to the cultured cells to examine the effects of stimulation on the labeling with [¹⁴C]2-DG at the single cell level. Electrical current stimulation increased [¹⁴C]2-DG uptake in CG and DRG neurons. The increase depended on frequency of the stimulation. These effects were potentiated by the application of tetraethylammonium, but suppressed by tetrodotoxin. Externally applied potassium ions increased the [¹⁴C]2-DG uptake in the CG cell, depending logarithmically on the concentration of applied KC1. The concentration-dependent increase agreed with potassium effect on the equilibrium potential. For CG cells, acetylcholine (ACh), glutamate, γ-aminobutyric acid (GABA) and glycine induced remarkable increases of the [¹⁴C]2-DG uptake, while dopamine did not induce any change. For DRG cells, GABA and glycine facilitated the [¹⁴C]2-DG uptake, while ACh, glutamate and dopamine did not have any significant effects on it. These facilitatory actions of neurotransmitters on the [¹⁴C]2-DG uptake are mostly consistent with the excitatory effects of the substrates on both CG and DRG cells in culture. The results suggest that the [¹⁴C]2-DG uptake in single cells is intimately correlated with action potential generation and change in the resting potential.     

Imaging endogenous opioid peptide release with [11C]carfentanil and [3H]diprenorphine: influence of agonist-induced internalization

Understanding the cellular processes underpinning the changes in binding observed during positron emission tomography neurotransmitter release studies may aid translation of these methodologies to other neurotransmitter systems. We compared the sensitivities of opioid receptor radioligands, carfentanil, and diprenorphine, to amphetamine-induced endogenous opioid peptide (EOP) release and methadone administration in the rat. We also investigated whether agonist-induced internalization was involved in reductions in observed binding using subcellular fractionation and confocal microscopy. After radioligand administration, significant reductions in [¹¹C]carfentanil, but not [³H]diprenorphine, uptake were observed after methadone and amphetamine pretreatment. Subcellular fractionation and in vitro radioligand binding studies showed that amphetamine pretreatment only decreased total [¹¹C]carfentanil binding. In vitro saturation binding studies conducted in buffers representative of the internalization pathway suggested that μ-receptors are significantly less able to bind the radioligands in endosomal compared with extracellular compartments. Finally, a significant increase in μ-receptor-early endosome co-localization in the hypothalamus was observed after amphetamine and methadone treatment using double-labeling confocal microscopy, with no changes in δ- or κ-receptor co-localization. These data indicate carfentanil may be superior to diprenorphine when imaging EOP release in vivo, and that alterations in the ability to bind internalized receptors may be a predictor of ligand sensitivity to endogenous neurotransmitter release.     

Does intracellular release of Ca participate in the afterhyperpolarization of a sympathetic neurone?

The afterhyperpolarization (AHP) of an action potential in the bullfrog sympathetic ganglion cell was highly sensitive to anions (a factor affecting Ca²⁺ release¹⁶) filled in a recording electrode; it was slower for citrate ion than for Cl⁻. The AHP recorded with a ‘KCl-electrode’ was suppressed drastically by D-600 (Ca²⁺-antagonist⁶) and prolonged significantly by caffeine (promoting Ca²⁺ release^4,9), while the AHP recorded with a ‘K₃-citrate-electrode’ was affected only slightly by these agents. Thus, these results suggest that Ca²⁺ entry during an action potential is the main origin of Ca²⁺ for the AHP recorded with a ‘KCl-electrode’, and favour the idea that the intracellular release of Ca²⁺ by an action potential as well as the Ca²⁺ influx participates in the mechanism of the AHP recorded with a ‘K₃-citrate-electrode’.     

Recovery of function and basal ganglia [C]2-deoxyglucose uptake after nigrostriatal injury

Rats with unilateral 6-hydroxydopamine injections along the mesotelencephalic dopaminergic projection showed a profound impairment in localizing somatosensory stimuli on the contralateral body surface at 3 days postoperatively. Approximately one-half of the affected animals recovered the ability to localize tactile stimuli during 6 weeks postoperatively, whereas the remainder did not. When it occurred, the recovery of sensorimotor function began between the third and fifth day postoperatively and plateaued between days 14 and 21.Unilateral damage to these dopaminergic neurons resulted in hemispheric asymmetries of [¹⁴C]2-deoxyglucose incorporation at 3 days postoperatively. For structures that normally receive a dopaminergic innervation (e.g., neostriatum, nucleus accumbens septi, olfactory tubercle) the autoradiographic density of the injured side was decreased relative to the intact hemisphere. For structures that receive striatal inputs (globus pallidus, entopeduncular nucleus, substantia nigra pars reticulata), the autoradiographic density was increased on the side of the injury.This pattern of altered [¹⁴C]2-deoxyglucose incorporation was still present at 6 weeks postoperatively in animals that showed no recovery of somatosensory localization during that time. In contrast, rats that did recover showed no hemispheric asymmetries within the anterior neostriatum, globus pallidus, or substantia nigra pars reticulata at 6 weeks postoperatively, and the time course of normalization of metabolic activity in these structures was similar to that for behavioral restoration.These results directly demonstrate the importance of the neostriatum and particular structures efferent to it in the recovery of sensorimotor functions after striatal dopamine depletion. The types of neuronal plasticity within this basal ganglia circuitry responsible for the normalization of [¹⁴C]2-deoxyglucose incorporation and behavior are discussed.     

PET imaging of serotoninergic neurotransmission with [11C]DASB and [18F]altanserin after focal cerebral ischemia in rats

The use of selective serotonin reuptake inhibitors has shown functional improvement after stroke. Despite this, the role of serotoninergic neurotransmission after cerebral ischemia evolution and its involvement in functional recovery processes are still largely unknown. For this purpose, we performed in parallel in vivo magnetic resonance imaging and positron emission tomography (PET) with [¹¹C]DASB and [¹⁸F]altanserin at 1, 3, 7, 14, 21, and 28 days after middle cerebral artery occlusion (MCAO) in rats. In the ischemic territory, PET with [¹¹C]DASB and [¹⁸F]altanserin showed a dramatic decline in serotonin transporter (SERT) and 5-HT_2A binding potential in the cortex and striatum after cerebral ischemia. Interestingly, a slight increase in [¹¹C]DASB binding was observed from days 7 to 21 followed by the uppermost binding at day 28 in the ipsilateral midbrain. In contrast, no changes were observed in the contralateral hemisphere by using both radiotracers. Likewise, both functional and behavior testing showed major impaired outcome at day 1 after ischemia onset followed by a recovery of the sensorimotor function and dexterity from day 21 to day 28 after cerebral ischemia. Taken together, these results might evidence that SERT changes in the midbrain could have a key role in the functional recovery process after cerebral ischemia.     

Lead increases tetrodotoxin-insensitive spontaneous release of glutamate and GABA from hippocampal neurons

This study was aimed at investigating the effects of the environmental pollutant lead (Pb2+) on the tetrodotoxin (TTX)-insensitive release of neurotransmitters from hippocampal neurons. Evidence is provided that Pb2+ (>/=100 nM) increases the frequency of gamma-aminobutyric acid (GABA)- and glutamate-mediated miniature postsynaptic currents (MPSCs) recorded by means of the patch-clamp technique from cultured hippocampal neurons. Because Pb2+ changed neither the amplitude nor the decay-time constant of the MPSCs, Pb2+-induced changes in MPSC frequency are exclusively due to a presynaptic action of this heavy metal. Increase by Pb2+ of the action potential-independent release of GABA and glutamate was concentration dependent and was only partially reversible upon washing of the neurons with nominally Pb2+-free external solution. This effect was also Ca2+ independent and began approximately after 1-2-min exposure of the neurons to Pb2+. The latency for the onset of the Pb2+'s effect on the MPSC frequency and the inability of the chelator ethylenediaminetetraacetic acid (100 microM) to reverse the effect that remained after washing of the neurons with external solution suggested that Pb2+ acted via an intracellular mechanism. Of interest also was the finding that Pb2+ simultaneously increased the release of GABA and glutamate, overriding the ability of these neurotransmitters to decrease the release of one another. Given that synaptic activity is a key mechanism for the establishment of stable synaptic connections early in the development, it is possible that, by interfering with spontaneous transmitter release, Pb2+ has lasting effects on neuronal maturation and plasticity.     

Activation of caudal brainstem cell groups during the exercise pressor reflex in the cat as elucidated by 2-[C]deoxyglucose

Cell groups of the caudal brainstem were labeled with 2-[14C]deoxyglucose during the pressor response evoked by contraction of hindlimb muscles (exercise pressor reflex). The nuclear groups which were labeled in excess of control levels included: the lateral reticular nucleus, the inferior olive (medial accessory olive), and the lateral tegmental field (adjacent to the lateral reticular nucleus).     

Reference region automatic extraction in dynamic [11C]PIB

The positron emission tomography (PET) radiotracer [¹¹C]Pittsburgh Compound B (PIB) is a marker of amyloid plaque deposition in brain, and binding potential is usually quantified using the cerebellum as a reference where the specific binding is negligible. The use of the cerebellum as a reference, however, has been questioned by the reported cerebellar [¹¹C]PIB retention in familial Alzheimer''s disease (AD) subjects. In this work, we developed a supervised clustering procedure for the automatic extraction of a reference region in [¹¹C]PIB studies. Supervised clustering models each gray matter voxel as the linear combination of three predefined kinetic classes, normal and lesion gray matter, and blood pool, and extract reference voxels in which the contribution of the normal gray matter class is high. In the validation with idiopathic AD subjects, supervised clustering extracted reference voxels mostly in the cerebellum that indicated little specific [¹¹C]PIB binding, and total distribution volumes of the extracted region were lower than those of the cerebellum. Next, the methodology was applied to the familial AD cohort where the cerebellar amyloid load had been demonstrated previously, resulting in higher binding potential compared with that obtained with the cerebellar reference. The supervised clustering method is a useful tool for the accurate quantification of [¹¹C]PIB studies.     

Olfactory bulbectomy reduces cerebral glucose utilization: 2-[14C]deoxyglucose autoradiographic study

The olfactory bulbectomized (OBX) rat is an extensively investigated animal model of depression. In the present study the effects of olfactory bulbectomy in drug-naive adult male Sprague–Dawley rats (200–240 g) on global (gCGU) and regional cerebral glucose (rCGU) utilization was evaluated. Two weeks following surgery, the autoradiographic measurement of CGU using [¹⁴C]-2-deoxyglucose was employed. The levels of CGU in the OBX and sham-operated rats were compared in 40 brain regions. Statistical methods indicate significantly lower levels of global (overall) CGU in the OBX group than in the sham group. Discriminant analysis was done on the z-scores to remove animal to animal variability. The following thirteen regions were identified by the stepwise discriminant analysis of the z-scores as significantly contributing to the differences between the sham and OBX: amygdala, cingulate cortex, caudate putamen at the level of globus pallidus, caudate putamen-lateral part, dorsal subiculum, dorsal thalamus, hypothalamus, median raphe, somatosensory cortex, substantia nigra, ventral hippocampus, ventral tegmental area and the ventral thalamus. The pattern of changes in the rCGU following OBX does not completely correlate with the pattern of connectivity of the olfactory bulbs, however, many regions with direct connection to the olfactory bulbs (e.g., amygdala, hypothalamus, ventral hippocampus, and ventral tegmental area) were found to be important for differentiation. No left to right asymmetries in the rCGU were found. The data suggest that there are very important regional differences in glucose utilization between the OBX and sham operated rats, which points to the need to study antidepressants in an animal model of depression rather than in normal animals.     

Regional differences in binding of [H]LSD and [H]L-HT in calf hippocampal slices revealed by radioautography and rapid filtration studies

Previous radioautographic experiments demonstrated that binding sites labeled by [³H]5-HT and [³H]LSD in rat brain were seen in all layers of CA1, CA4 and the dentate gyrus but not in fields CA2 and CA3 of the hippocampus. In an attempt to confirm this observation we performed binding assays on homogenates from selected areas of calf hippocampus since the small size of the rat hippocampus precluded using preparations from this animal for this purpose. Studies on homogenates from calf hippocampal regions, were done after we determined that the binding to slices in vitro was similar in the calf and rat. Binding of both [³H]5-HT and [³H]LSD by homogenates of CA1 and dentate gyrus, but not of CA3, was saturable. These studies show that the qualitative differences in binding site distribution within the calf hippocampus seen by radioautography reflect quantitative differences in the densities of binding sites revealed by the homogenate studies.     

Reduced subcortical glutamate/glutamine in adults with autism spectrum disorders: a [1H]MRS study

Dysfunctional glutamatergic neurotransmission has been implicated in autism spectrum disorder (ASD). However, relatively few studies have directly measured brain glutamate in ASD adults, or related variation in glutamate to clinical phenotype. We therefore set out to investigate brain glutamate levels in adults with an ASD, comparing these to healthy controls and also comparing results between individuals at different points on the spectrum of symptom severity. We recruited 28 adults with ASD and 14 matched healthy controls. Of those with ASD, 15 fulfilled the ‘narrowly'' defined criteria for typical autism, whereas 13 met the ‘broader phenotype''. We measured the concentration of the combined glutamate and glutamine signal (Glx), and other important metabolites, using proton magnetic resonance spectroscopy in two brain regions implicated in ASD—the basal ganglia (including the head of caudate and the anterior putamen) and the dorsolateral prefrontal cortex—as well as in a parietal cortex ‘control'' region. Individuals with ASD had a significant decrease (P<0.001) in concentration of Glx in the basal ganglia, and this was true in both the ‘narrow'' and ‘broader'' phenotype. Also, within the ASD sample, reduced basal ganglia Glx was significantly correlated with increased impairment in social communication (P=0.013). In addition, there was a significant reduction in the concentration of other metabolites such as choline, creatine (Cr) and N-acetylaspartate (NAA) in the basal ganglia. In the dorsolateral prefrontal cortex, Cr and NAA were reduced (P<0.05), although Glx was not. There were no detectable differences in Glx, or any other metabolite, in the parietal lobe control region. There were no significant between-group differences in age, gender, IQ, voxel composition or data quality. In conclusion, individuals across the spectrum of ASD have regionally specific abnormalities in subcortical glutamatergic neurotransmission that are associated with variation in social development.     

A pharmacological model for studying the role of Na gradients in the modulation of synaptosomal free [Ca]i levels and energy metabolism

Lactate production (J_lac), oxygen consumption rate (Q_O2), plasma membrane potentials (E_m) and cytosolic free calcium levels [Ca²⁺]_i were studied on symaptosomes isolated from rat brains, incubated in presence of high doses of nicardipine (90 μM), diltiazem (0.5 mM) and verapamil (0.25 mM), and submitted to depolarizing stimulation or inhibition of mitochondrial respiration. Nicardipine was able to completely prevent the veratridine-induced stimulation ofJ_lac, Q_O2andE_m depolarization, whereas diltiazem and verapamil were less effective, although the concentrations used were 5 and 3 times higher, respectively, than nicardipine. Diltiazem, verapamil and nicardipine (9 μM) also prevented the veratridine-induced increase in [Ca²⁺]_i, this effect being much less pronounced if the drugs were added after veratridine. Monensin (20 μM) was also able to increase [Ca²⁺]_i but this effect was not affected by verapamil. Synaptosomes were also submitted to an inhibition of respiration of intrasynaptic mitochondria by incubation with rotenone (5 μM); in this condition of mimicked hypoxiaE_m was more positive of about 11 mV; none of the drugs utilized modified this situation. The rotenone-induced 3-fold increase inJ_lac was barely modified by diltiazem and verapamil but it was completely abolished by nicardipine. The possible mechanism of the counteracting action of the drugs towards veratridine stimulation and rotenone inhibition and the involvement of Na⁺/Ca²⁺ exchanger in affecting [Ca²⁺]_i are discussed.     

Metabolic mapping of the rat brain involved in thermoregulatory responses using the [C]2-deoxyglucose technique

The central nervous structures involved in thermoregulatory responses to thermal stimulation of the preoptic/anterior hypothalamic region were investigated in conscious, unrestrained rats by means of the 2-deoxy-d-[¹⁴C]glucose autoradiographic technique. Significant activation in metabolic activity was observed in the medial preoptic area, medial forebrain bundle, anterior part of ventromedial hypothalamus, anteroventral thalamus, dorsomedial thalamus, basal ganglia, pars compacta of substantia nigra, red nucleus and the reticular formation.     

Involvement of calmodulin-dependent protein kinases-I and -IV in long-term potentiation

Multifunctional Ca²⁺/calmodulin-dependent protein kinases (CaMKs) are thought to be involved in the induction of long-term potentiation (LTP). In the present study, LTP was induced by theta burst stimulation in the Schaffer collateral area of the stratum radiatum in the hippocampal CA1 region of the rat hippocampus. LTP-induced and control hippocampal slices were studied by Western blot and immunohistochemical analyses using CaMK-I, -II and -IV antibodies. Increased amounts of all three CaMKs were found in LTP-induced hippocampal slices as indicated by Western blot as well as by the density of their immunoreactivity. Our data clearly shows that not only CaMK-II but also CaMK-I and -IV contribute to synaptic plasticity formed in LTP.