The distribution of calcium-binding proteins in the lateral geniculate nucleus and visual cortex of a New World monkey, the marmoset, Callithrix jacchus

Antibodies directed against the calcium-binding proteins, parvalbumin and calbindin, can be used to label distinct neuronal subgroups in the primate visual pathway. We analyzed parvalbumin immunoreactivity (P-IR) and calbindin immunoreactivity (C-IR) in the lateral geniculate nucleus (LGN) and visual cortex of the marmoset, Callithrix jacchus. We compared marmosets which were identified as having dichromatic or trichromatic color vision. Within the LGN, the density of P-IR neurones is highest in the parvocellular and magnocellular laminae, but C-IR neurones are found mainly in the koniocellular division of the LGN, that is, the interlaminar zones and S laminae. Not all interlaminar zone cells are C-IR. In the visual cortex, P-IR neurones are present in all laminae except lamina 1, in areas V1 and V2. Neurones which are strongly C-IR are mainly located in laminae 2 and 3 in V1 and V2. Lightly C-IR neurones are concentrated in lamina 4, and are more numerous in V1 than in V2. Quantitative analysis showed no differences in the density or distribution of IR neurones in either LGN or visual cortex when dichromat and trichromat animals were compared. We conclude that this functional difference is not associated with differences in the neurochemistry of calcium-binding proteins in the primary visual pathways.     

Chemoarchitectonic subdivisions of the visual pulvinar in monkeys and their connectional relations with the middle temporal and rostral dorsolateral visual areas, MT and DLr

The organization of the inferior pulvinar complex (PI) in squirrel monkeys was studied with histochemical localization of the calcium binding proteins calbindin-D28k and parvalbumin, and of cytochrome oxidase. With each of these markers, the inferior pulvinar complex can be subdivided into four distinct regions. Calbindin-D28k immunoreactivity is densely distributed in cells and neuropil within PI, except for a distinct centromedially located gap. This calbindin-poor zone, termed the medial division of the inferior pulvinar (PIM), corresponds precisely to a region that contains elevated cytochrome oxidase activity and parvalbumin immunostaining. The PIM extends slightly above and behind the classically defined limit of the inferior pulvinar, the corticotectal tract. Regions of inferior pulvinar with intense immunostaining for calbindin-D28k were the posterior division of the inferior pulvinar (PIP, medial to PIM) and the central division (PIC, lateral to PIM). A newly recognized lateral region, PIL, adjoins the lateral geniculate nucleus and stains more lightly for calbindin and parvalbumin immunoreactivity and for cytochrome oxidase. Staining patterns for calbindin, parvalbumin, and cytochrome oxidase in the pulvinar of rhesus monkeys closely resemble those shown in squirrel monkey inferior pulvinar, suggesting that a common organization exists in all primates. In order to examine cortical connection patterns of the histochemically defined compartments in the inferior pulvinar, injections of up to five neuroanatomical tracers (wheat germ agglutinin conjugated to horseradish peroxidase and fluorescent retrograde tracers) were placed in the same cerebral hemisphere. Single injection sites were in the middle temporal area (MT), and several separate injections were placed in a strip corresponding to the rostral subdivision of the dorsolateral area (DLr). Injections that involved only DLr and not MT labeled principally the PIC, and more sparsely PIP and PIL. DLr connections occupied a "shell" region dorsal to PIM that extended from PIC into the lateral and medial divisions of the pulvinar, PL and PM. Injection sites that included MT or were largely restricted to MT produced dense label in PIM and moderate label in PIC and PIL. The retinotopic organization within the inferior pulvinar was inferred from patterns of connections. Connections with cortex related most closely to central vision were found posteriorly in PIM and in adjacent portions of PIC as it wraps around the caudal pole of PIM. Cortex related to more peripheral locations in the lower visual field connected with more rostral PIM and PIC. Patterns of label within the portions of PL and PM that were immediately adjacent to PIM roughly paralleled those in PIM and PIC.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparative analysis of calcium-binding protein-immunoreactive neuronal populations in the auditory and visual systems of the bottlenose dolphin (Tursiops truncatus) and the macaque monkey (Macaca fascicularis)

This study compares the distribution of three calcium-binding protein-immunoreactive (CaBP-immunoreactive) neuronal populations (calretinin-, calbindin- and parvalbumin-immunoreactive) in the visual and auditory systems in two mammalian species which are fundamentally different in their evolutionary traits and ecology, the aquatic toothed whale Tursiops truncatus (bottlenose dolphin) and the terrestrial Old World primate, Macaca fascicularis (long-tailed macaque). Immunocytochemical analyses, combined with computerized morphometry revealed that in the visual and auditory systems of the bottlenose dolphin, calretinin and calbindin are the prevalent calcium-binding proteins, whereas parvalbumin is present in very few neurons. The prevalence of calretinin and calbindin-immunoreactive neurons is especially obvious in the auditory system of this species. In both auditory and visual systems of the macaque monkey, the parvalbumin-immunoreactive neurons are present in comparable or higher densities than the calretinin and calbindin-immunoreactive neurons. In some structures of the visual and auditory systems of the macaque monkey, the calretinin- and calbindin-immunoreactive neurons are nearly absent. The prevalence of parvalbumin-immunoreactive over calretinin- and calbindin-immunoreactive neurons is particularly prominent in the visual system of primates. Thus, the dominant sensory systems in both aquatic and terrestrial mammals are enriched in specific phenotypes of calcium-binding protein-immunoreactive neurons.     

The development of parvalbumin and calbindin-D28k immunoreactive interneurons in kitten visual cortical areas

Calbindin-D and parvalbumin are calcium binding proteins which are found in non-overlapping subpopulations of GABA-ergic interneurons in mammalian neocortex. We studied the development of these calcium-binding proteins in interneurons of cat striate and extrastriate cortical areas which have differing patterns of connectivity and follow different developmental timetables. We examined primary visual areas 17 and 18, secondary visual area 19, medial lateral suprasylvian and lateral suprasylvian areas (MLS and LLS) and association areas 7 and the splenial visual area from the day of birth (P0) through P101. Parvalbumin-immunoreactive (ir) interneurons followed the inside-out pattern of maturation of cortical laminae. They were located only in infragranular layers at the earliest ages and were not observed in the overlying cortical plate. At 3 weeks of age, when cortical lamination is mature, parvalbumin stained cells were found in all cortical layers except layer I. The number of stained secondary and tertiary dendrites in the parvalbumin-ir interneuronal population decreased with age. This change was associated with a shift in the molecular weight of parvalbumin detected on Western blots. During the first postnatal week, the area 17/18 border contained more parvalbumin-ir neurons than other visual areas. The developmental pattern of calbindin staining differed considerably from the parvalbumin staining pattern. Very few calbindin-ir interneurons were seen in area 17 during the first 2 weeks of life. In lateral cortical areas, calbindin-ir neurons were located in cortical plate, infragranular layers of cortex and white matter/subplate. Calbindin-ir neurons increased in supragranular layers of secondary cortical areas by P7 and in area 17 by P20. In the mature cortex, the calbindin staining pattern was bilaminar, with a dense band of calbindin-ir cells in layer II and a second band in layers V-VI. There was no difference in the distribution of calbindin-ir neurons among visual areas at maturity.     

Viewpoint: the core and matrix of thalamic organization

The integration of the whole cerebral cortex and thalamus during forebrain activities that underlie different states of consciousness, requires pathways for the dispersion of thalamic activity across many cortical areas. Past theories have relied on the intralaminar nuclei as the sources of diffuse thalamocortical projections that could facilitate spread of activity across the cortex. A case is made for the presence of a matrix of superficially-projecting cells, not confined to the intralaminar nuclei but extending throughout the whole thalamus. These cells are distinguished by immunoreactivity for the calcium-binding protein, D28K calbindin, are found in all thalamic nuclei of primates and have increased numbers in some nuclei. They project to superficial layers of the cerebral cortex over relatively wide areas, unconstrained by architectonic boundaries. They generally receive subcortical inputs that lack the topographic order and physiological precision of the principal sensory pathways. Superimposed upon the matrix in certain nuclei only, is a core of cells distinguished by immunoreactivity for another calcium-binding protein, parvalbumin, These project in highly ordered fashion to middle layers of the cortex in an area-specific manner. They are innervated by subcortical inputs that are topographically precise and have readily identifiable physiological properties. The parvalbumin cells form the basis for sensory and other inputs that are to be used as a basis for perception. The calbindin cells, especially when recruited by corticothalamic connections, can form a basis for the engagement of multiple cortical areas and thalamic nuclei that is essential for the binding of multiple aspects of sensory experience into a single framework of consciousness.     

Measurement of dynamic wedge angles and beam profiles by means of MRI ferrous sulphate gel dosimetry

The present study investigates, by immunocytochemistry, the behavior of different neuronal subpopulations of the rat hippocampus in neurodegenerative processes induced by the neurotoxicant trimethyltin. The calcium-binding proteins calbindin and parvalbumin are used as selective markers of different neuronal subpopulations. The effects of the neurotoxicant were apparent 21 days after a single i.p. administration with severe neuronal loss, which was significant in CAI and CA3, as revealed by cell counts after cresyl violet staining. Immunolabeling with calbindin D28-k (CB) and parvalbumin (PV) indicated severe cell loss of CB-containing neurons, essentially reflecting the generalized neuronal loss, while PV-containing neurons appeared to be selectively spared by the neurotoxicant-induced degeneration.     

Intracellular distributions and putative functions of calcium-binding proteins in the bullfrog vestibular otolith organs

Hair cells in the bullfrog vestibular otolith organs were immunolabeled by monoclonal and polyclonal antisera against calbindin (CaB), calmodulin (CaM), calretinin (CaR), and parvalbumin (PA). S-100, previously shown to immunolabel striolar hair cells in fish vestibular organs, only weakly immunolabeled hair cells in the bullfrog vestibular otolith organs. Immunolabeling was not detected in supporting cells. With the exception of CaR, myelinated axons and unmyelinated nerve terminals were immunolabeled by all of the above antisera. Immunolabeling was seen in all saccular hair cells, although hair cells at the macular margins were immunolabeled more intensely for CaB, CaM, and PA than more centrally located hair cells. As the macula margins are known to be a growth zone, this labeling pattern suggests that marginal hair cells up-regulate their calcium-binding proteins during hair cell development. In the utriculus, immunolabeling for CaM and PA was generally restricted to striolar hair cells. CaR immunolabeling was restricted to the stereociliary array. Immunolabeling for other calcium-binding proteins was generally seen in both the cell body and hair bundles of hair cells, although this labeling was often localized to the stereociliary array and the apical portion of the cell body. CaM and PA immunolabeling in the stereociliary array in saccular and utricular striolar cells suggests a functional role for these proteins in mechanoelectric transduction and adaptation.     

Patchy and laminar terminations of medial geniculate axons in monkey auditory cortex

The object of this study was to identify the terminal distributions of thalamocortical axons arising in chemically characterized subdivisions of the medial geniculate complex. Large injections of wheat germ agglutinin-conjugated horseradish peroxidase or small injections of Phaseolus vulgaris leucoagglutinin were made in the medial geniculate complex of Macaca fuscata. The terminal distributions of labeled axons in the cortex were correlated with auditory cortical fields demonstrable by different intensities of immunoreactivity for parvalbumin. Fibers from the ventral nucleus terminated mainly in layer IV and deep portion of layer III (IIIB), with additional terminations in layers I-IIIA and in layer VI. In layers IIIB-IV, a major terminal plexus was formed by a small number of dense patches, 300-500 microns in diameter, surrounded by smaller satellite patches. The patches conformed to a similarly lobulated pattern of parvalbumin fiber immunoreactivity. Terminations of some individually labeled thalamocortical fibers were restricted to a single patch, whereas others innervated more than one patch by collateral branches. Fibers from the dorsal nuclei ending in areas of less dense parvalbumin immunoreactivity surrounding the primary auditory cortex formed much larger terminal patches centered largely in layer IIIB. Fibers from the magnocellular nucleus had relatively few terminal branches but innervated extremely wide areas by collaterals of single axons. Two types of axons arose from the magnocellular nucleus, one terminating preferentially in middle cortical layers and the other exclusively in layer I. These may arise respectively from parvalbumin- and calbindin-immunoreactive cell populations in the magnocellular nucleus.     

Coexistence of calcium-binding proteins in vagal and glossopharyngeal sensory neurons of the rat

The presence and coexistence of the calcium-binding proteins (CaBPs), calbindin D-28k, parvalbumin and S100 protein, were immunohistochemically examined in the glossopharyngeal and vagal sensory ganglia, the carotid body and taste buds. The CaBPs were found in each ganglion with the nodose ganglion containing the largest number of CaBP-immunoreactive (ir) cells (calbindin D-28k > or = S100 > parvalbumin). The coexistence of CaBPs was found in neurons of the nodose, petrosal, and jugular ganglia. Calbindin D-28k-ir neurons in the nodose and petrosal ganglia frequently colocalized S100-ir whereas calbindin D-28k-ir neurons in the jugular ganglion less frequently contained S100-ir. Only small percentages of calbindin D-28k-ir neurons in each ganglion colocalized parvalbumin. Similarly, S100-ir neurons in the nodose and petrosal ganglia frequently colocalized calbindin D-28k-ir whereas S100-ir neurons in the jugular ganglion less frequently contained calbindin D-28k-ir. Moderate to small percentages of S100-ir neurons in each ganglion colocalized parvalbumin. Parvalbumin-ir neurons nearly always colocalized S100-ir in the nodose, petrosal and jugular ganglia. Moderate to small percentages of parvalbumin-ir neurons in each ganglion colocalized calbindin D-28k. Whereas calbindin D-28k- and S100-ir were colocalized in nerve fibers and cells within taste buds of circumvallate papilla of the tongue, the coexistence of these CaBPs could not be determined in the carotid body. These findings suggest a co-operative role for CaBPs in the functions of subpopulations of nodose and petrosal ganglia neurons.     

Histopathological changes in Yucatan minipig skin following challenge with sulphur mustard. A sequential study of the first 24 hours following challenge

The importance of calcium in neuronal function has been amply demonstrated in recent years. The discovery of a class of proteins within neurons which bind calcium, therefore, has proven to be a catalyst for the generation of theories and hypotheses regarding mechanisms of neurotoxicity in the CNS. In addition, the distribution of certain calcium-binding proteins changes during neural development, suggesting that they may play a role in organization or pattern generation. We have examined the ontogeny of three related calcium-binding proteins, calbindin-D28, parvalbumin and calretinin, with respect to the ventral and dorsal compartments or tiers of the dopaminergic population in the ventral midbrain. Single and dual-label immunocytochemistry was employed to map the distributions of calcium-binding proteins and tyrosine hydroxylase from E18 through adulthood. The results show that each of the three proteins exhibits a unique developmental sequence and compartment preference, with calbindin D28 clearly related to the later-developing dorsal tier, and parvalbumin and calretinin to the ventral tier of the dopaminergic ventral mesencephalon.     

Neuronal subpopulations of developing rat hippocampus containing different calcium-binding proteins behave distinctively in trimethyltin-induced neurodegeneration

The present study investigates, by immunocytochemistry, the behavior of different neuronal subpopulations of the developing rat hippocampus, selectively labeled by the calcium-binding proteins calbindin D28-k (CB), parvalbumin (PV), and calretinin (CR), in neurodegenerative processes induced by the neurotoxicant trimethyltin (TMT). Previous studies on adult rats indicated that CB-immunoreactive (IR) neurons were affected by TMT, while PV- and CR-IR neurons were selectively spared. The present findings show that only CR-IR neurons are spared in developing rats, and in addition the number of CR-IR neurons are significantly higher in the DG of treated animals. On the contrary, PV-IR neurons, spared in adult rats, were affected by TMT during development. CB-IR neurons were affected also in developing rats, as in adults. The different postnatal time-courses of calcium-binding protein expression in relationship to the time of TMT administration (presence of CR but absence of PV) could have a role in the different behavior of CR- and PV-IR cells in developing rats.     

A possible role of transient AChE expression in the medial geniculate of developing rats

Acetylcholinesterase (AChE) and calbindin D-28K (CaBP) are transiently expressed in the rat auditory nuclei during the early postnatal period. In the ventral division of the medial geniculate body (MGV), the transient AChE expression in the neuropil is replaced by CaBP expression in the neurones. The time correlation between the up- and down-regulations in these neuro-chemicals suggests some switching over mechanism. A lesion of the inferior colliculus (IC) decreases the AChE reactivity in terminal field of the IC-MGV projections. We here demonstrate that the IC lesion results in CaBP expressions in neurones of the MGV before its normal onset. It is thus possible that the transiently expressed AChE plays an important role in the intercellular signal transduction for neurochemical phenotype expressions.     

Transarterial embolization of the uterine arteries: patient reactions and effects on uterine vasculature

Corticotropin releasing hormone (CRH) has been localized to interneurons of the mammalian cerebral cortex, but these neurons have not been fully characterized. The present study determined the extent of co-localization of CRH with glutamate decarboxylase (GAD) and calcium-binding proteins in the infant rat neocortex using immunocytochemistry. CRH-immunoreactive (ir) neurons were classified into two major groups. The first group was larger and consisted of densely CRH-immunostained small bipolar cells, predominantly localized to layers II and III. The second group of CRH-ir cells was lightly labeled and included multipolar neurons mainly found in deep cortical layers. Co-localization studies indicated that the vast majority of CRH-ir neurons, including both bipolar and multipolar types, was co-immunolabeled for GAD-65 and GAD-67. Most multipolar, but only some bipolar, CRH-ir neurons also contained parvalbumin, while CRH-ir neurons rarely contained calbindin or calretinin. These results indicate that virtually all CRH-ir neurons in the rat cerebral cortex are GABAergic. Furthermore, since parvalbumin is expressed by cortical basket and chandelier cells, the co-localization of CRH and parvalbumin suggests that some cortical CRH-ir neurons may belong to these two cell types.     

Relative resistance of striatal neurons containing calbindin or parvalbumin to quinolinic acid-mediated excitotoxicity compared to other striatal neuron types

To evaluate the relative ability of those striatal neuron types containing calbindin or parvalbumin to withstand a Ca(2+)-mediated excitotoxic insult, we injected the NMDA receptor-specific excitotoxin quinolinic acid (QA) into the striatum in mature adult rats and 2 months later examined the relative survival of striatal interneurons rich in parvalbumin and striatal projection neurons rich in calbindin. To provide standardization to the survival of striatal neuron types thought to be poor in Ca2+ buffering proteins, the survival was compared to that of somatostatin-neuropeptide Y (SS/NPY)-containing interneurons and enkephalinergic projection neurons, which are devoid of or relatively poorer in such proteins. The various neuron types were identified by immunohistochemical labeling for these type-specific markers and their relative survival was compared at each of a series of increasing distances from the injection center. In brief, we found that parvalbuminergic, calbindinergic, and enkephalinergic neurons all showed a generally comparable gradient of neuronal loss, except just outside the lesion center, where calbindin-rich neurons showed significantly enhanced survival. In contrast, striatal SS/NPY interneurons were more vulnerable to QA than any of these three other types. These observed patterns of survival following intrastriatal QA injection suggest that calbindin and parvalbumin content does not by itself determine the vulnerability of striatal neurons to QA-mediated excitotoxicity in mature adult rats. For example, parvalbuminergic striatal interneurons were not impervious to QA, while cholinergic striatal interneurons are highly resistant and SS/NPY+ striatal interneurons are highly vulnerable. Both cholinergic and SS/NPY+ interneurons are devoid of any known calcium buffering protein. Similarly, calbindin does not prevent striatal projection neuron vulnerability to QA excitotoxicity. Nonetheless, our data do suggest that calbindin may offer striatal neurons some protection against moderate excitotoxic insults, and this may explain the reportedly slightly greater vulnerability of striatal neurons that are poor in calbindin to ischemia and Huntington's disease.     

Tonotopic organization of auditory cortical fields delineated by parvalbumin immunoreactivity in macaque monkeys

Tonotopic maps, obtained from single and multi-unit recordings in the primary and surrounding areas of the auditory cortex, were related to chemoarchitecture of the supratemporal plane, as delineated by immunoreactivity for parvalbumin. Neurons in the central core were sharply tuned and formed two complete tonotopic representations corresponding to the primary auditory area (AI) and the rostral (R) area. High frequencies were represented posteriorly in AI and anteriorly in R, the representation reversing in the anterior part of the core. Neurons in regions of less dense immunostaining previously described as lateral (L) and posteromedial (P-m) fields, showed broader frequency tuning. Two tonotopic representations were found in L: in an anterolateral (AL) field, corresponding to a field previously reported by others, high frequencies were represented anteriorly and low frequencies posteriorly; in a posterolateral field (PL) the trend reversed. There was a further reversal on entering P-m from the high frequency representation in PL and progressively lower frequencies tended to be represented more medially in P-m, but P-m may contain two representations reported by others. Neurons in the previously described anteromedial (A-m) and medial (M) fields of weaker immunostaining, were even more broadly tuned. A tonotopic progression from low frequency representation posteriorly to high frequency representation anteriorly was observed in the medial field. Frequency representation in A-m remains uncertain. No tonotopic representation could be demonstrated with the stimuli used in the zones of very weak parvalbumin immunostaining outside AL, PL, P-m, A-m, and M. The properties of neurons in the core and surrounding zones are likely to reflect inputs from the ventral and dorsal medial geniculate nuclei, respectively. The fields outside the core seem to be the starting points for separate streams of auditory corticocortical connections passing into association cortex.     

The differential in vitro stimulation of 3',5'-cyclic nucleotide phosphodiesterase by calcium binding proteins

A heterogeneous class of proteins exhibit within their sequence a particular structure, named EF-hand, able to bind calcium with high affinity. These calcium binding proteins have been described in most cells and tissues and are suggested to work as calcium buffers, thereby participating in the regulation of calcium-dependent cellular activity. Recent circumstantial evidences suggest that calcium binding proteins may serve other functions as well, possibly as enzyme modulators. Since 3',5'-cyclic nucleotide phosphodiesterase is a well-known calmodulin-modulated enzyme, in this work we studied the effect in vitro of different purified calcium binding proteins on the activity of this enzyme. Among the proteins tested, calmodulin and recombinant rat brain parvalbumin could stimulate the 3',5'-cyclic nucleotide phosphodiesterase activity in vitro, whereas rabbit muscle parvalbumin, rat renal and brain calbindin D28K, and bovine brain S-100B were ineffective. Immunoprecipitation with the specific antiserum completely abolished either calmodulin or recombinant brain parvalbumin activation of 3',5'-cyclic nucleotide phosphodiesterase. Moreover, while the presence of calcium in the incubation mixture was critical in the calmodulin-mediated stimulation of the enzyme, it did not modify the effect of the recombinant brain parvalbumin. We suggest that, in addition to calmodulin, parvalbumin may be a regulator of 3',5'-cyclic nucleotide phosphodiesterase, and possibly of other yet to be identified enzymes in certain tissues.     

Recognition and management of childhood cardiac arrhythmias

Axonal connections between the amygdala and the hypothalamic paraventricular nucleus were examined by combined anterograde-retrograde tract tracing. Iontophoretic injections of the retrograde tracer Fluorogold were placed in the paraventricular nucleus, and the anterograde tracer PHA-L in the ipsilateral central or medial amygdaloid nuclei. Single and double-label immunohistochemistry were used to detect tracers. Single label anterograde and retrograde tracing suggest limited evidence for direct connections between the central or medial amygdala and the paraventricular nucleus. In general, scattered PHA-L-positive terminals were seen in autonomic subdivisions of the paraventricular nucleus (lateral parvocellular, dorsal parvocellular and ventral medial parvocellular subnuclei) following central or medial amygdaloid nucleus injection. Double-label studies indicate that central and medial amygdaloid nucleus efferents contact paraventricular nucleus-projecting cells in several forebrain nuclei. In the case of central nucleus injections, PHA-L positive fibers occasionally contacted Fluorogold-labeled neurons in the anteromedial, ventromedial and preoptic subnuclei of the bed nucleus of the stria terminalis. Overall, such contacts were quite rare, and did not occur in the bed nucleus of the stria terminalis regions showing greatest innervation by the central amygdaloid nucleus. In contrast, medial amygdala injections resulted in a significantly greater overlap of PHA-L labeling and Fluorogold-labeled neurons, with axosomatic appositions observed in medial divisions of the bed nucleus of the stria terminalis, anterior hypothalamic area and preoptic area. The results provide anatomical evidence that a substantial proportion of amygdaloid connections with hypophysiotrophic paraventricular nucleus neurons are likely multisynaptic, relaying in different subregions of the bed nucleus of the stria terminalis and hypothalamus.     

Medial auditory thalamic nuclei are necessary for eyeblink conditioning.

The auditory conditioned stimulus (CS) pathway that is necessary for delay eyeblink conditioning was investigated with induced lesions of the medial auditory thalamus contralateral to the trained eye in rats. Rats were given unilateral lesions of the medial auditory thalamus or a control surgery followed by twenty 100-trial sessions of delay eyeblink conditioning with a tone CS and then five sessions of delay conditioning with a light CS. Rats that had complete lesions of the contralateral medial auditory thalamic nuclei, including the medial division of the medial geniculate, suprageniculate, and posterior intralaminar nucleus, showed a severe deficit in conditioning with the tone CS. Rats with complete lesions also showed no cross-modal facilitation (savings) when switched to the light CS. The medial auditory thalamic nuclei may modulate activity in a short-latency auditory CS pathway or serve as part of a longer latency auditory CS pathway that is necessary for eyeblink conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A pilot study of the air quality in dental environments

Quantitative autoradiographic techniques were used to compare the distribution of GABAA, GABAB, and glycine receptors in the subcortical auditory pathway of the big brown bat, Eptesicus fuscus. For GABAA receptors, the ligand used was 35S-t-butylbicyclophosphorothionate (TBPS) for GABAB receptors, 3H-GABA was used as a ligand in the presence of isoguvacine to block binding to GABAA sites; for glycine, the ligand used was 3H-strychnine. In the subcortical auditory nuclei there appears to be at least a partial complementarity in the distribution of GABAA receptors labeled with 35S-TBPS and glycine receptors labeled with 3H-strychnine, GABAA receptors were concentrated mainly in the inferior colliculus (IC) and medial geniculate nucleus, whereas glycine receptors were concentrated mainly in nuclei below the level of the IC. Within the IC, there was a graded spatial distribution of 35S-TBPS binding; the most dense labeling was in the dorsomedial region, but very sparse labeling was observed in the ventrolateral region. There was also a graded spatial distribution of 3H-strychnine binding. The most dense labeling was in the ventral and lateral regions and the weakest labeling was in the dorsomedial region. Thus, in the IC, the distribution of 35S-TBPS was complementary to that of 3H-strychnine. GABAB receptors were distributed at a low level throughout the subcortical auditory nuclei, but were most prominent in the dorsomedial part of the IC.