GABA-containing Neurons Research Articles

Interaction between substance P-immunoreactive central terminals and γ-aminobutyric acid-immunoreactive elements in synaptic glomeruli in the lamina II of the chicken spinal cord

We investigated the interaction between γ-aminobutyric acid (GABA)-immunoreactive (IR) elements and substance P (SP)-IR central terminals in synaptic glomeruli in lamina II of the chicken spinal cord in order to ascertain how pain information is modulated in the spinal dorsal horn. We combined the peroxidase-antiperoxidase (PAP) technique and the protein A-gold (PAG) technique to observe the synaptic relationship between these two components. At the light microscopic level, we observed both GABA-IR and SP-IR elements in the lamina II. GABA-IR elements were also observed in the lamina III. At the electron microscopic level, the following three GABA-IR elements formed synapses with the SP-IR central terminals in synaptic glomeruli: (1) elements which appeared to be axon terminals containing tightly-packed pleomorphic clear vesicles; (2) elements which appeared to be vesicle-containing dendrites with loosely-packed clear and dense-cored vesicles (DCVs); and (3) dendrites without synaptic vesicles. The first type of element was always presynaptic to the SP-IR central terminal. The second type was postsynaptic, presynaptic or in some cases reciprocal to the SP-IR central terminals. The third type was postsynaptic to the SP-IR central terminal. These results suggest that the SP-containing primary afferents activate GABA-containing dendrites and that the SP-containing primary afferents are inhibited presynaptically by GABA-containing neurons through axo-axonic and dendro-axonic synapses.

The pattern of excitatory inputs to the nucleus tractus solitarii evoked on stimulation in the hypothalamic defence area in the cat.

1. In anaesthetized, paralysed and artificially ventilated cats, recordings have been made in the nucleus tractus solitarii (NTS) to assess further the role of this nucleus in mediating the cardiorespiratory responses that are elicited on stimulation within the hypothalamic defence area (HDA). 2. The responses of NTS neurones to stimulation in the hypothalamus were assessed, as were their patterns of evoked response to electrical stimulation of the sinus (SN), aortic (AN), superior laryngeal (SLN) and vagus (VN) nerves. 3. Stimulation in the HDA affected the activity of 110 NTS neurones (85 studied in intracellular and 25 studied in extracellular recordings). The present study focused on those sixty-eight neurones that were excited by such stimulation (51 intracellular recordings and 17 extracellular recordings). 4. Of the sixty-eight neurones that were excited by HDA stimulation, seven revealed no changes in membrane potential or evoked discharge (2 neurones) but the stimulus facilitated the excitatory effects of stimulating either (or both) the SN and SLN. An additional group of neurones showed powerful excitatory responses to HDA stimulation (15 studied with extracellular and 35 with intracellular recording). Evoked EPSPs had onset latencies in the range of 1-30 ms. Of those thirty-five neurones displaying EPSPs, twenty-six were shown to receive convergent inputs on nerve stimulation. In nine neurones the early EPSP in response to HDA stimulation was followed by an IPSP. 5. In a further group of neurones HDA stimulation elicited a long-lasting IPSP, but this was not analysed further because its features have been described in detail in earlier studies from this laboratory. 6. The patterns of response of several neurones excited by stimulation in the HDA are consistent with them forming a group of NTS interneurones that mediate the hypothalamically evoked cardiovascular responses, including modulation of reflex function, which is a major feature of cardiorespiratory control. This possibility is discussed in the light of the present physiological observations and descriptions of an intrinsic NTS group of GABA-containing neurones that have been suggested to fulfil such a role.

Minireview: Cell protective role of melatonin in the brain

In recent years an increasing amount of data has been published involving melatonin in the control of brain function. The pineal gland exerts a depressive influence on CNS excitability. This activity is linked to melatonin, since pharmacological doses of the hormone prevent seizures in several animal models. In addition, melatonin also has analgesic properties in these species. However, the sites and mechanism of melatonin action are not known. A role for the pineal gland and its hormone melatonin as a homeostatic system controlling brain excitability has been proposed, and GABA-containing neurons may be involved in some central action of melatonin. There is evidence supporting a role of melatonin in the regulation of the GABA-benzodiazepine receptor complex, and it appears that melatonin potentiates this inhibitory neurotransmitter system in brain. Melatonin does not bind to GABA or benzodiazepine binding sites themselves, because in vitro binding data showed that melatonin is a weak competitor of benzodiazepine binding in brain membranes at concentrations greater than 10(-5) M. The effect of melatonin on brain activity also involves the participation of corticotropic and opioid peptides, and the existence of an opioid-antiopioid homeostatic system is proposed, with the GABA-benzodiazepine receptor complex as an effector. Moreover, the interaction of melatonin with corticotropic peptides and mitochondrial benzodiazepine receptors may result in a participation of neurosteroids in the control of GABA activity and function. The most recently available data from biochemical and electrophysiological studies support the possibility that the anticonvulsant and depressive effects of melatonin on neuron activity may depend on its antioxidant and antiexcitotoxic roles, acting as a free radical scavenger and regulating brain glutamate receptors. The full characterization of the nuclear melatonin receptor explains the genomic effects of melatonin, opening a new perspective regarding actions and roles of melatonin as a cellular protector.

GABA-containing neurons in the ventral tegmental area project to the nucleus accumbens in rat brain

The ventral tegmental area receives a gamma-aminobutyric acid (GABA) innervation from the nucleus accumbens and contains GABA immunoreactive neurons believed to be interneurons. We combined the immunocytochemical detection of retrogradely transported Fluoro-Gold (FG) from the nucleus accumbens (Acb) with the detection of GABA within the same section of tissue in the ventral tegmental area (VTA) of the rat brain to determine whether there might also be reciprocal GABAergic projections in the mesolimbic pathway. Immunoperoxidase labeling for FG and immunohold-silver labeling for GABA were most readily distinguished within perikarya and dendrites in sections examined by electron microscopy. Ultrastructural observations indicated that 36% (n = 110) of the FG-labeled perikarya and dendrites also contained GABA immunoreactivity. The present results provide the first evidence that GABA is contained in a subpopulation of neurons in the mesolimbic pathway from the VTA to the Acb. The reciprocity of this circuitry may provide an important feedback loop thus facilitating inhibition of motor activity.

Postnatal Development of GABA Neurons in the Rat Somatosensory Barrel Cortex: A Quantitative Study

As an estimate of the numerical importance of GABA-containing neurons during development, their quantitative distribution was analysed in the primary somatosensory cortex of rats between postnatal days (P) 5 and 60, using the dissector method and GABA postembedding immunocytochemistry. In relation to the overall number of neurons in the barrel field cortex, the proportion of GABA neurons showed an early significant decrease between P5 and P10 from 14 to 11%, most likely due to termination of transient expression of GABA by some cells. It then remained stable until P20, after which it started slowly but steadily to increase, reaching 14% of the total at P60. The absolute number of GABA neurons also increased by nearly 50% during that period, whereas the number of all neurons remained constant. These changes are seemingly due to a subpopulation of neurons, shown to be of small size, which express GABA late in development. Thus, anatomical adjustments of the cortical GABA system may be observed at least until the end of the second postnatal month, reflecting both delayed maturation and adaptation of this inhibitory circuitry. We suggest the existence of three subpopulations of cortical GABA neurons depending on the time of onset and the regulation of their GABA expression: (i) neurons which express GABA before completion of migration and thus provide for its neurotrophic influence, (ii) neurons which express GABA immediately after completion of migration and build up the cortical inhibitory circuitry, and (iii) neurons which express GABA later in development and represent a substrate of experience-dependent plasticity.

Anesthetic Implications in Stiff-Person Syndrome

A 46-yr-old female presented to the operating room for repair of an intrathecal baclofen pump. Her diagnosis of SPS was based on clinical presentation and the presence of an autoantibody against the central nervous system enzyme glutamic acid decarboxylase (GAD). The syndrome began as muscle stiffness in her lower extremities and insidiously progressed to a state of constant stiffness resulting in permanent contractures of her lower extremities and moderate rigidity of her upper extremities. The patient’s facial, cervical, and extraocular muscles were spared. When startled by a loud noise, the patient experienced a painful brisk spasm resulting in opisthotonic posturing. These acute exacerbations were treated with a 50-mg dose of diazepam administered intramuscular. Other pharmacologic therapies included intrathecal baclofen and 100 mg of diazepam orally per day. Past surgical history was significant for a 2-day history of prolonged postoperative weakness after the baclofen pump was inserted, and an overdose of baclofen was suggested as the cause. A review of the previous anesthetic record revealed that propofol and succinylcholine followed by desflurane was used for induction of anesthesia, tracheal intubation, and maintenance of anesthesia, respectively. Anesthesia was induced with sufentanil 10 pg, thiopental 375 mg (5.8 mg/kg), and vecuronium 8 mg (0.12 mg/kg) administered intravenously (IV). It was inferred from the slow and inadequate induction of anesthesia that the IV catheter had infiltrated subcutaneously although visual inspection was equivocal. A facial nerve train-of-four twitch monitor indicated an absence of all four twitches 10 min after induction of anesthesia. Inhalation anesthesia via a

Anesthetic Implications in Stiff-Person Syndrome

Anesthetic Implications in Stiff-Person Syndrome

Glutamate and GABAergic neurointeractions in the monkey hypothalamus: a quantitative immunomorphological study.

Glutamate (Glu) and gamma-aminobutyric acid (GABA) are the most abundant excitatory and inhibitory neurotransmitters in the mammalian hypothalamus. Glu and GABA-containing neurons have both been shown to synapse with gonadotropin-releasing hormone (GnRH) and other neuroendocrine systems in the hypothalamus of several species. Since their direct interactions could play a pivotal role in governing neuroendocrine function, we performed double-label immunostaining for Glu and for glutamic acid decarboxylase (GAD) as a marker for GABAergic neurons in hypothalamic sections from adult female cynomolgus monkeys. Ultrastructural analysis of 785 Glu-immunoreactive (-ir) and GAD-ir elements in the medial septum (MS), arcuate nucleus-ventral hypothalamic tract (VHT1), supraoptic nucleus (SON), paraventricular nucleus (PVN), and median eminence (ME) revealed that 63% were Glu-ir, 28% were GAD-ir, and 9% were Glu + GAD-ir. In addition, we observed surprisingly consistent labeling of 2-4% somata (SOM), 65-80% dendrites (DEN), and 15-30% axons and terminals (AXO) in all of these areas. Characterization of 177 interactions (36% synapses, 64% contacts) by pre/post-transmitter content indicated that 29% contained Glu/GAD, 15% Glu/Glu, and 15% Glu/Glu + GAD, while 16% were unlabeled/Glu, 9% were unlabeled/GAD, and 16% expressed other transmitter combinations. Regional analysis of these interactions showed that 43% occurred in the MS, 22% in VHT1, 14% in SON, 9% in PVN, and 12% in the ME. AXO/DEN interactions made up 51% of all labeled interactions characterized, and were comprised 29% of Glu/GAD, 22% of Glu/Glu, and 18% of the Glu/Glu, and 18% of the Glu/Glu + GAD type. AXO/DEN synapses were more prevalent than contacts in all areas except the PVN and of course the ME, where anatomical synapses do not occur. AXO/SOM interactions represented approximately 15% of all those identified, and were predominantly unlabeled/Glu (71%) and unlabeled/GAD (18%) synapses. Almost all (95%) AXO/SOM synapses and 75% of the contacts occurred in the MS. DEN/DEN interactions, 28% of the total, were composed 50% of Glu/GAD, 12% of Glu/Glu, and 18% of the Glu/Glu+GAD type. The relatively few DEN/DEN synapses all appeared in the MS, whereas much more abundant DEN/DEN contacts were more widely distributed. DEN/SOM interactions, 6% of the total, appeared only as contacts, with the majority (60%) again located in the MS. In addition, the MS contained 48% of all asymmetrical synapses (vs. 35% in VHT1 and 17% in SON), 62% of all symmetrical synapses (vs. 19% in VHT1 and 14% in SON), and 35% of all contacts (vs. 21% in VHT1 and 12% in SON) identified.(ABSTRACT TRUNCATED AT 400 WORDS)

Basic fibroblast growth factor increases the number of excitatory neurons containing glutamate in the cerebral cortex.

Stem cells isolated from the ventricular zone of embryonic day 12.5 rat telencephalon progressively proliferate and differentiate in vitro into three major classes of amino acid-containing neurons, glutamate, aspartate, and GABA. We quantitatively examined the effect of basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) on amino acid-containing neurons. bFGF caused a threefold increase in glutamate-containing neurons, while the number of GABA- and aspartate-containing neurons was not significantly changed. In contrast, NGF did not alter the number of amino acid-containing neurons. The ratio of glutamate- to GABA-containing neurons in untreated or NGF-treated cultures was 0.6:1. In the bFGF-treated cultures, this ratio was 1.4:1, which closely approximates the ratio in the cerebral cortex in vivo. Treatment with antisense oligonucleotides targeted to bFGF mRNA provoked a 50% decrease in the number of glutamate-containing neurons but had no significant effect on the GABA-containing neurons. Thus, diffusible factors such as bFGF may play an important role in determining the relative proportion of excitatory versus inhibitory neurons in the cerebral cortex by selectively regulating the proliferation of stem cells committed to different neurotransmitter phenotypes.

Immunocytochemical localization of GABAA receptors in rat somatosensory cortex and effects of tactile deprivation.

Immunocytochemical techniques were used to investigate the distribution of gamma-aminobutyric acidA (GABAA) receptors in the rat primary somatosensory cortex (SI). Monoclonal antibody 62-3G1 (de Blas et al., 1988; Victorica et al., 1988), which recognizes an epitope common to the beta 2 and beta 3 subunits of the GABAA receptor, produces staining of small punctate structures throughout the neuropil, and around somata and linear processes in all laminae of SI. Receptor immunostaining is relatively intense in upper lamina I and in lamina IV, where patches of intense receptor staining are interleaved with narrow zones of moderate immunoreactivity. Staining is lightest in lamina Vb, where stained puncta appear to be aligned with radially oriented processes, and moderate in the remaining laminae. Tangential sections through lamina IV reveal that each large cortical barrel encompasses several patches of intense receptor staining that are aligned with the corners or edges of individual barrels; interbarrel septa are moderately of intense cytochrome oxidase (CO) histochemical staining. A similar correspondence is apparent between a complex lattice of dense receptor clustering and a plexus of dark CO staining in the cortical trunk representation. Six to eight weeks of tactile deprivation produced by simple whisker trimming have no visible effect on GABAA receptor distribution. This is the case for rats whose whiskers were trimmed only during adulthood and for rats deprived from the day of birth until examination 6-8 weeks later. However, electrocautery ablation of whisker follicles leads to a marked decline in GABAA receptor immunoreactivity in cortical barrels associated with the ablated follicles. Our findings indicate that there is reasonable, though not perfect, correspondence between the distribution of GABAA receptors and the distribution of GABA-containing neurons and terminals in rat SI. These elements are associated with regions of intense oxidative metabolic activity revealed by CO staining. The density of GABAA receptors is reduced in lamina IV following complete loss of peripheral afferent input. However, less severe tactile deprivation, which is known to affect cortical neuron responsiveness, produces little or no change in receptor distribution.

GABAergic and non-GABAergic neurons in the nucleus of the optic tract project to the superior colliculus: an ultrastructural retrograde tracer and immunocytochemical study in the rabbit.

Both the nucleus of the optic tract (NOT) and the superior colliculus (SC) are thought to play important roles in the regulation of eye movements. The superior colliculus contributes to visual orientation and saccades, and the nucleus of the optic tract contributes to the detection of slow movements of the visual surround. Recently, a GABAergic projection has been described between these two nuclei in the cat, a species with frontal vision. The present study aimed at determining whether a similar GABAergic pathway exists in the rabbit, a species with lateral vision. To study this pathway we used the retrograde tracer cholera-toxin (CTB) to identify NOT neurons projecting to the SC and GABA-antibody immunostaining to identify GABA-containing neurons and processes. CTB injections into the superficial laminae of the SC showed that GABAergic and non-GABAergic neurons in the NOT project to the SC. Both types of neurons have structural characteristics similar to other projection neurons in the NOT. In contrast to the NOT neurons projecting to the inferior olive (IO) which are mainly located in the rostral NOT, the GABAergic and non-GABAergic NOT-SC neurons are situated throughout the nucleus. The somata and principal dendrites of both neuron types receive numerous synaptic contacts from GABAergic terminals and only a few from retinals. The NOT projection neurons to the SC thus establish prominent excitatory and inhibitory links between the two structures, suggesting the existence of separate circuits that could interact through a GABAergic and non-GABAergic NOT-SC projection. It is further suggested that these circuits may be involved in the regulation of saccades in the SC during optokinetic nystagmus.

Localization of mRNAs encoding two forms of glutamic acid decarboxylase in the rat hippocampal formation

The mRNAs for two forms of glutamic acid decarboxylase (GAD65 and GAD67) were localized in the rat hippocampal formation by nonradioactive in situ hybridization methods with digoxigenin-labeled cRNA probes. Some neurons in all layers of the hippocampus and dentate gyrus were readily labeled for each GAD mRNA, and the patterns of labeling for GAD65 and GAD67 mRNAs were very similar. All major groups of previously described GAD- and GABA-containing neurons appeared to be labeled for each GAD mRNA. Such findings suggest that most GABA neurons in the hippocampal formation contain both GAD mRNAs. When the labeling of neurons in the hippocampal formation and cerebral cortex was compared in the same sections, the intensity of neuronal labeling for GAD67 mRNA was generally similar in the two regions. However, the intensity of labeling for GAD65 mRNA was generally stronger for many neurons in the hippocampal formation than for most neurons in the cerebral cortex. Neurons in the hilus of the dentate gyrus were particularly well labeled for GAD65. The nonradioactive labeling for the GAD mRNAs was confined to the cytoplasm of neuronal cell bodies, and this allowed a clear visualization of the relative number and location of labeled neurons. Several distinct patterns of GAD mRNA-containing neurons were observed among different regions of the hippocampal formation. In the hilus of the dentate gyrus, GAD mRNA-containing neurons were numerous in the regions deep to the granule cell layer as well as in more central parts of the hilus. Within CA3, the densities (quantities) of labeled neurons varied among the regions. In the inner or hilar segment of CA3, the density of labeled neurons was often lower than that in the outer part of CA3 where numerous labeled neurons were distributed throughout all layers. In CA1, GAD mRNA-labeled neurons were distributed in a relatively laminar pattern with the highest density in stratum pyramidale and moderate densities in stratum oriens and at the interface between strata radiatum and lacunosum-moleculare. Lower densities were found within the latter two layers. The prominent localization of the two GAD mRNAs in the hippocampal formation suggests that a dual system for GABA synthesis is necessary for normal GABAergic function in this brain region. Most putative GABA neurons contain relatively high levels of GAD67 mRNA as might be expected if this GAD form is responsible for the synthesis of GABA for metabolic and baseline synaptic function.(ABSTRACT TRUNCATED AT 400 WORDS)

Gamma-Aminobutyric acid in the nervous system of a planarian.

The amino acid gamma-aminobutyric acid (GABA) is an important inhibitory neurotransmitter in both vertebrates and invertebrates. Despite this, no reports of GABA in flatworms have to date been published. We have studied the presence of GABA in the planarian Dugesia tigrina with immunocytochemical methods and high-pressure liquid chromatography. Fibers showing GABA-like immunoreactivity (GABA-IR) were present in abundance in the longitudinal nerve cords and lateral nerves. GABA-IR was revealed in fibers forming commissures in the brain. The ventral part of the subepidermal plexus showed GABA-IR. No cell somata containing GABA-IR could be identified with certainty. The chromatographic analysis showed that the average GABA concentration in D. tigrina is 533.6 pmol/mg protein. This is substantially higher than the concentrations of dopamine (62.87 pmol/mg) and serotonin (233.20 pmol/mg). An enzyme assay confirmed the capacity for GABA-synthesis in D. tigrina. The results indicate that GABA-containing neurons appeared earlier in evolution than was previously thought and that GABA may serve an important role already in the flatworms.

Evidence for the Colocalization of Parvalbumin and Glutamate, but Not GABA, in the Perforant Path of the Gerbil Hippocampal Formation: A Combined Immunocytochemical and Microquantitative Analysis

Gerbils (Meriones unguiculatus) are known for their seizure sensitivity, which is dependent on an intact perforant path from the entorhinal cortex to the hippocampus. In contrast with other species, the perforant path in gerbils contains parvalbumin, a cytosolic high-affinity calcium-binding protein. Parvalbumin is known to be present in a subpopulation of GABA-containing neurons and is thought to be responsible for their physiological characteristics of fast spiking activity and lack of spike adaptation. Therefore, the question arose of whether this projection in gerbils is GABAergic or glutamatergic as in other species. In a first approach to this question, the effect of lesioning the origin of the perforant path, the entorhinal cortex, on levels of GABA and glutamate was determined by enzymatic-luminometric assay in single layers of the dentate gyrus of lyophilized brain sections. Parallel sections were cryofixed using an acidified acetone-formaldehyde mixture at -20 degrees C for 48 h, and subsequently stained for parvalbumin immunocytochemistry. Seven days after ablation of the entorhinal cortex, parvalbumin staining was undetectable in the termination zone of the perforant path, the outer two-thirds of the stratum moleculare. In parallel, glutamate content was reduced to 80% of controls (and of the unoperated contralateral side) but unchanged in the inner third of the stratum moleculare and in stratum granulare. GABA content was not significantly altered by the lesion. From these results, we conclude that in the gerbil as in other species, the perforant path contains glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of glutamate- and GABA-immunoreactive neurons projecting to the cardioacceleratory center of the intermediolateral nucleus of the thoracic cord of SHR and WKY rats: a double-labeling study

We aimed at (1) determining the distribution of glutamate (Glu)- and γ-aminobutyric acid (GABA)-containing neurons in the brainstem with projections to the cardioacceleratory sympathetic preganglionic neurons in the intermediolateral nucleus (IML) of the upper thoracic cord and (2) determining whether such afferent projections in spontaneously hypertensive rats (SHR) differ from those of control Wistar-Kyoto (WKY) rats. We used a combination of electrophysiological methods to determine the site of HRP injection in the spinal cord and double-labeling methods for plotting the distribution of Glu- and GABA-immunoreactive neurons with projections to this site. HRP/Glu-labeled neurons (possibly glutamatergic) and HRP/GABA-labeled neurons (possibly GABAergic) were detected in 27% and 7% of the total HRP-labeled neurons of the central autonomic nuclei of 3 SHR rats and 3 WKY rats. HRP/Glu-labeled neurons were distributed predominantly ipsilaterally in 20 nuclei of the medulla oblongata, pons and hypothalamus, while HRP/GABA-labeled neurons were distributed in 7 nuclei of the medulla oblongata. No significant differences were found between the average percentages of HRP/Glu-labeled and HRP/GABA-labeled neurons in SHR and WKY rats. These findings indicate that: (1) the Glu-containing neurons represent a greater proportion than the GABA-containing neurons, (2) the proportions of these neurons appear to be similar in WKY and SHR rats and (3) generation of inbred tachycardia and hypertension in SHR rats can not be attributed to the topological and quantitative differences in the distribution of the glutamatergic and GABAergic neurons in the central autonomic nuclei.

Neuropsychological Implications of Brain Changes in Schizophrenia: An Overview

Schizophrenia is associated with structural changes in the brain but it is not clear whether the changes are localized. Studies in Manchester and elsewhere have reported abnormalities in biochemical markers of glutamate- and GABA-containing neurones in post-mortem brains from schizophrenic patients. The abnormalities occur in the ventral frontal cortex and anterior temporal lobe. It is suggested that these regions of the brain specifically encode information about social communication-language, gesture and facial expression. Many of the symptoms of schizophrenia become neuropsychologically understandable when seen as disturbances of social communication. In this and the following papers, experimental tests of this hypothesis are described.

Dopamnine‐Immunoreactive axon varicosities form nonrandom contacts with GABA‐immunoreactive neurons of rat medial prefrontal cortex

Recent postmortem studies have suggested that reduced gamma-aminobutyric acid (GABA)ergic activity in limbic cortex may be one component to the pathophysiology of schizophrenia. This hypothesis has underscored the importance of knowing whether midbrain dopamine afferents interact extensively enough with inhibitory interneurons to suggest a direct functional relationship. Toward this end, a double immunofluorescence approach combined with confocal laser scanning microscopy has been used to localize dopamine and GABA simultaneously in rat medial prefrontal cortex. The results confirm studies from other laboratories showing a rich network of dopamine-immunoreactive fibers forming a gradient across the cortical laminae, with deeper layers having the highest density. When viewed with oil immersion optics, dopamine-immunoreactive fibers were frequently found to be in close apposition with GABA-immunoreactive cell bodies. The percentage of GABA-containing neurons showing such contacts was highest in layer VI (65%) and progressively decreased toward layer I (9%). Varicose regions of the dopamine fibers were typically present at the point of contact with a GABA-immunoreactive cell body. Using an immunoperoxidase technique to localize dopamine fibers and cresyl violet staining to visualize neurons simultaneously, two separate statistical analyses were performed to assess whether the frequency of contacts between dopamine fibers and cell bodies in general may be due to random effects. In layer VI, a high percentage of both pyramidal and nonpyramidal neurons were found to be in contact with dopamine varicosities (71% and 76%, respectively), but these were not significantly different from that observed for GABA-containing cells (65%) in double-immunofluorescence specimens. A Chi-square statistical test was used to compare the observed and predicted number of varicosities forming cell body contacts. This analysis indicated that the percentage of dopamine varicosities (30%) that form appositions with cell bodies is much greater than would be expected if these appositions were due to random effects (15%). Moreover, using an estimate of intensity for a stationary Poisson process, it was again found that random effects can not account for these interactions (P = 0.01). Taken together with earlier electron microscopic studies from other laboratories, the present findings support the idea that GABAergic interneurons have extensive interactions with dopamine varicosities. While these interactions are not unique to GABAergic cell bodies, they suggest that inhibitory interneurons can play a direct role in mediating the effects of midbrain dopamine afferents in rat medial prefrontal cortex.

Neuronal Changes in the Cerebral Cortex of the Rat Following Alcohol Treatment and Thiamin Deficiency

The contribution of thiamin deficiency to the pathology of alcohol-related brain damage is still unclear. This study used a model of prolonged alcohol abuse in which animals were subjected to a brief period of mild thiamin deficiency. The episode of thiamin deficiency was early (after 4 weeks), in the middle (after 15 weeks) or late (after 26 weeks) in their 28 week alcohol treatment period. A control group of animals fed no alcohol and maintained on a thiamin-replete diet was used for comparison. The brains were removed and sectioned in the coronal plane at 50 microns intervals. Successive serial sections were stained with cresyl violet for Niss1 substance and immunohistochemically with antibodies to the calcium-binding proteins parvalbumin and calbindin. These calcium-binding proteins identify the majority of GABA-containing neurons in the cerebral cortex. The number of cells in the Fr1 region of the cerebral cortex was quantitated. A significant loss of Niss1-stained neurons was identified from the early group, while a loss of parvalbumin-immunoreactive neurons was seen in the early and middle groups. No loss of neurons was identified from the late group. In addition, no loss of calbindin-immunoreactive neurons was seen. This study represents the first report of cortical neuronal loss in an animal model of alcohol abuse and thiamin deficiency. Moreover, the results imply that thiamin deficiency is integrally involved in the pathogenesis of alcohol-related cortical neuronal loss.

Immunohistochemical localization of γ-aminobutyric acid- and aspartate-containing neurons in the guinea pig superior olivary complex

The immunohistochemical localization of γ-aminobutyric acid (GABA)- and aspartate-containing neurons was demonstrated in the guinea pig superior olivary complex, using purified antisera to GABA and aspartate, respectively. Medium-sized oval GABA-containing neurons were found in the lateral superior olive, and bipolar medium-sized GABA-containing neurons were observed in the dorsal hilus of the lateral superior olive. Medium-sized to large round GABA-containing neurons were observed in the ventral nucleus of the trapezoid body. GABA-containing terminals were found throughout the superior olivary complex with the highest density in the ventral nucleus of the trapezoid body. Aspartate-like immunoreactivity was observed in medium-sized round or oval neurons in the lateral superior olive, small fusiform neurons in the ventral nucleus of the trapezoid body, fusiform medium-sized neurons in the medial superior olive and oval medium-sized neurons in the superior paraolivary nucleus and round medium-sized neurons in the medial nucleus of the trapezoid body. Double staining method demonstrated that aspartate-containing neurons in the medial nucleus of the trapezoid body were surrounded by GABA-containing terminals. The present results suggested the possible origin of GABAergic and aspartatergic olivocochlear bundles.

Synaptic neurochemistry of human striatum during development: changes in sudden infant death syndrome.

There is evidence of abnormalities in the brain-stem monoamine-containing neurons in infants with sudden infant death syndrome (SIDS). By taking advantage of the rich innervation of the human basal ganglia by monoaminergic afferents from cell bodies in the brainstem, we studied the synaptic chemistry of catecholamine and associated neurons of the putamen obtained postmortem from 14 SIDS infants, eight age-matched control infants, and older control subjects of various ages. We found significantly lower concentrations of dopamine and higher homovanillic acid/DA ratios in samples from SIDS infants compared with age-matched control infants. Noradrenaline and 5-hydroxytryptamine were lower in SIDS compared with control subjects, but the difference did not reach statistical significance. There was no clear evidence that dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid were altered. Immunoblot analysis of striatal tissue showed that samples from infants with SIDS, which exhibited lower DA, also had lower tyrosine hydroxylase protein. Other transmitter-specific neuronal markers were also assessed, including enzymes associated with cholinergic and GABA-containing neurons. We found significantly decreased choline acetyltransferase activities. However, GABA, glutamate, or somatostatin concentrations or monoamine oxidase activities were unchanged in SIDS. We also noted age-dependent changes in brain weights and some synaptic markers by comparing the age-matched infants with older control subjects. Analysis of variance revealed that homovanillic acid, dihydroxyphenylacetic acid, and monoamine oxidase B activities were increased with age. DA and choline acetyltransferase were also found to be positively correlated in putamen. Our findings suggest developmental changes in some transmitter-specific neurons in SIDS that may result from apneic episodes or chronic hypoxia induced before death.