Ultrastructural and optogenetic dissection of V1 corticotectal terminal synaptic properties.

The superior colliculus (SC) is a major site of sensorimotor integration in which sensory inputs are processed to initiate appropriate motor responses. Projections from the primary visual cortex (V1) to the SC have been shown to exert a substantial influence on visually induced behavior, including "freezing." However, it is unclear how V1 corticotectal terminals affect SC circuits to mediate these effects. To investigate this, we used anatomical and optogenetic techniques to examine the synaptic properties of V1 corticotectal terminals. Electron microscopy revealed that V1 corticotectal terminals labeled by anterograde transport primarily synapse (93%) on dendrites that do not contain gamma aminobutyric acid (GABA). This preference was confirmed using optogenetic techniques to photoactivate V1 corticotectal terminals in slices of the SC maintained in vitro. In a mouse line in which GABAergic SC interneurons express green fluorescent protein (GFP), few GFP-labeled cells (11%) responded to activation of corticotectal terminals. In contrast, 67% of non-GABAergic cells responded to activation of V1 corticotectal terminals. Biocytin-labeling of recorded neurons revealed that wide-field vertical (WFV) and non-WFV cells were activated by V1 corticotectal inputs. However, WFV cells were activated in the most uniform manner; 85% of these cells responded with excitatory postsynaptic potentials (EPSPs) that maintained stable amplitudes when activated with light trains at 1-20 Hz. In contrast, in the majority of non-WFV cells, the amplitude of evoked EPSPs varied across trials. Our results suggest that V1 corticotectal projections may initiate freezing behavior via uniform activation of the WFV cells, which project to the pulvinar nucleus.

Distributions of vesicular glutamate transporters 1 and 2 in the visual system of tree shrews (Tupaia belangeri).

Vesicular glutamate transporter (VGLUT) proteins regulate the storage and release of glutamate from synapses of excitatory neurons. Two isoforms, VGLUT1 and VGLUT2, are found in most glutamatergic projections across the mammalian visual system, and appear to differentially identify subsets of excitatory projections between visual structures. To expand current knowledge on the distribution of VGLUT isoforms in highly visual mammals, we examined the mRNA and protein expression patterns of VGLUT1 and VGLUT2 in the lateral geniculate nucleus (LGN), superior colliculus, pulvinar complex, and primary visual cortex (V1) in tree shrews (Tupaia belangeri), which are closely related to primates but classified as a separate order (Scandentia). We found that VGLUT1 was distributed in intrinsic and corticothalamic connections, whereas VGLUT2 was predominantly distributed in subcortical and thalamocortical connections. VGLUT1 and VGLUT2 were coexpressed in the LGN and in the pulvinar complex, as well as in restricted layers of V1, suggesting a greater heterogeneity in the range of efferent glutamatergic projections from these structures. These findings provide further evidence that VGLUT1 and VGLUT2 identify distinct populations of excitatory neurons in visual brain structures across mammals. Observed variations in individual projections may highlight the evolution of these connections through the mammalian lineage.

Distribution, morphology, and synaptic targets of corticothalamic terminals in the cat lateral posterior-pulvinar complex that originate from the posteromedial lateral suprasylvian cortex.

The lateral posterior (LP) nucleus is a higher order thalamic nucleus that is believed to play a key role in the transmission of visual information between cortical areas. Two types of cortical terminals have been identified in higher order nuclei, large (type II) and smaller (type I), which have been proposed to drive and modulate, respectively, the response properties of thalamic cells (Sherman and Guillery [1998] Proc. Natl. Acad. Sci. U. S. A. 95:7121-7126). The aim of this study was to assess and compare the relative contribution of driver and modulator inputs to the LP nucleus that originate from the posteromedial part of the lateral suprasylvian cortex (PMLS) and area 17. To achieve this goal, the anterograde tracers biotinylated dextran amine (BDA) or Phaseolus vulgaris leucoagglutinin (PHAL) were injected into area 17 or PMLS. Results indicate that area 17 injections preferentially labelled large terminals, whereas PMLS injections preferentially labelled small terminals. A detailed analysis of PMLS terminal morphology revealed at least four categories of terminals: small type I terminals (57%), medium-sized to large singletons (30%), large terminals in arrangements of intermediate complexity (8%), and large terminals that form arrangements resembling rosettes (5%). Ultrastructural analysis and postembedding immunocytochemical staining for gamma-aminobutyric acid (GABA) distinguished two types of labelled PMLS terminals: small profiles with round vesicles (RS profiles) that contacted mostly non-GABAergic dendrites outside of glomeruli and large profiles with round vesicles (RL profiles) that contacted non-GABAergic dendrites (55%) and GABAergic dendritic terminals (45%) in glomeruli. RL profiles likely include singleton, intermediate, and rosette terminals, although future studies are needed to establish definitively the relationship between light microscopic morphology and ultrastructural features. All terminals types appeared to be involved in reciprocal corticothalamocortical connections as a result of an intermingling of terminals labelled by anterograde transport and cells labelled by retrograde transport. In conclusion, our results indicate that the origin of the driver inputs reaching the LP nucleus is not restricted to the primary visual cortex and that extrastriate visual areas might also contribute to the basic organization of visual receptive fields of neurons in this higher order nucleus.

Investigations of the cholinergic modulation of GABA release in rat thalamus slices.

The thalamus receives a dense cholinergic projection from the pedunculopontine tegmentum. A number of physiological studies have demonstrated that this projection causes a dramatic change in thalamic activity during the transition from sleep to wakefulness. Previous anatomical investigations have found that muscarinic type 2 receptors are densely distributed on the dendritic terminals of GABAergic interneurons, as well as the somata and proximal dendrites of GABAergic cells in the thalamic reticular nucleus. Since these structures are the synaptic targets of cholinergic terminals in the thalamus, it appears likely that thalamic pedunculopontine tegmentum terminals can activate muscarinic type 2 receptors on GABAergic cells. To test whether activation of muscarinic type 2 receptors affects the release of GABA in the thalamus, we have begun pharmacological studies using slices prepared from the rat thalamus. We have found that the application of the nonspecific muscarinic agonist, methacholine, and the muscarinic type 2-selective agonist, oxotremorine.sesquifumarate, diminished both the baseline, and K(+) triggered release of [(3)H]GABA from thalamic slices. This effect was calcium dependent, and blocked by the nonselective muscarinic antagonist atropine, the muscarinic type 2-selective antagonist, methoctramine, but not the muscarinic type 1 antagonist, pirenzepine. Thus, it appears that one function of the pedunculopontine tegmentum projection is to decrease the release of GABA through activation of muscarinic type 2 receptors. This decrease in inhibition may play an important role in regulating thalamic activity during changes in states of arousal.

Synaptic targets of thalamic reticular nucleus terminals in the visual thalamus of the cat.

A major inhibitory input to the dorsal thalamus arises from neurons in the thalamic reticular nucleus (TRN), which use gamma-aminobutyric acid (GABA) as a neurotransmitter. We examined the synaptic targets of TRN terminals in the visual thalamus, including the A lamina of the dorsal lateral geniculate nucleus (LGN), the medial interlaminar nucleus (MIN), the lateral posterior nucleus (LP), and the pulvinar nucleus (PUL). To identify TRN terminals, we injected biocytin into the visual sector of the TRN to label terminals by anterograde transport. We then used postembedding immunocytochemical staining for GABA to distinguish TRN terminals as biocytin-labeled GABA-positive terminals and to distinguish the postsynaptic targets of TRN terminals as GABA-negative thalamocortical cells or GABA-positive interneurons. We found that, in all nuclei, the TRN provides GABAergic input primarily to thalamocortical relay cells (93-100%). Most of this input seems targeted to peripheral dendrites outside of glomeruli. The TRN does not appear to be a significant source of GABAergic input to interneurons in the visual thalamus. We also examined the synaptic targets of the overall population of GABAergic axon terminals (F1 profiles) within these same regions of the visual thalamus and found that the TRN contacts cannot account for all F1 profiles. In addition to F1 contacts on the dendrites of thalamocortical cells, which presumably include TRN terminals, another population of F1 profiles, most likely interneuron axons, provides input to GABAergic interneuron dendrites. Our results suggest that the TRN terminals are ideally situated to modulate thalamocortical transmission by controlling the response mode of thalamocortical cells.

Y retinal terminals contact interneurons in the cat dorsal lateral geniculate nucleus.

One of the largest influences on dorsal lateral geniculate nucleus (dLGN) activity comes from interneurons, which use the neurotransmitter gamma-aminobutyric acid (GABA). It is well established that X retinogeniculate terminals contact interneurons and thalamocortical cells in complex synaptic arrangements known as glomeruli. However, there is little anatomical evidence for the involvement of dLGN interneurons in the Y pathway. To determine whether Y retinogeniculate axons contact interneurons, we injected the superior colliculus (SC) with biotinylated dextran amine (BDA) to backfill retinal axons, which also project to the SC. Within the A lamina of the dLGN, this BDA labeling allowed us to distinguish Y retinogeniculate axons from X retinogeniculate axons, which do not project to the SC. In BDA-labeled tissue prepared for electron microscopic analysis, we subsequently used postembedding immunocytochemical staining for GABA to distinguish interneurons from thalamocortical cells. We found that the majority of profiles postsynaptic to Y retinal axons were GABA-negative dendrites of thalamocortical cells (117/200 or 58.5%). The remainder (83/200 or 41.5%) were GABA-positive dendrites, many of which contained vesicles (59/200 or 29.5%). Thus, Y retinogeniculate axons do contact interneurons. However, these contacts differed from X retinogeniculate axons, in that triadic arrangements were rare. This indicates that the X and Y pathways participate in unique circuitries but that interneurons are involved in the modulation of both pathways.

A novel means of Y cell identification in the developing lateral geniculate nucleus of the cat.

We examined the postnatal development of putative Y cells in the dorsal lateral geniculate nucleus (dLGN) using the SMI-32 antibody, which has been demonstrated in the adult cat to stain cells with Y cell morphology. At birth, SMI-32 stained cells were concentrated in the interlaminar zones. During postnatal development, the SMI-32 staining gradually becomes more disperse and by P21 stained cells are found throughout the A and magnocellular C laminae. By the end of the first postnatal week, and in all later ages examined, the SMI-32 stained cells were significantly larger than the overall population of Nissl stained cells and interneurons (stained with an antibody against glutamic acid decarboxylase). Postnatal SMI-32 staining revealed a dramatic increase in soma sizes and the expansion of putative geniculate Y cell dendritic arbors that continued past the second postnatal month. In contrast, the growth of interneurons appeared to be complete by 3-4 postnatal weeks, at which time cell somas stained with SMI-32 have only reached a little over one half of their adult size. Similar to the adult cat, SMI-32 appears to selectively stain the Y cell population during development and may provide a useful morphological marker to examine the participation of Y cells in the developing postnatal circuitry of the dLGN. This further establishes the cat dLGN as a novel model system to study the normal function and pathological reorganization of neurofilaments.

Neurotransmitters contained in the subcortical extraretinal inputs to the monkey lateral geniculate nucleus.

The lateral geniculate nucleus (LGN) is the thalamic relay of retinal information to cortex. An extensive complement of nonretinal inputs to the LGN combine to modulate the responsiveness of relay cells to their retinal inputs, and thus control the transfer of visual information to cortex. These inputs have been studied in the most detail in the cat. The goal of the present study was to determine whether the neurotransmitters used by nonretinal afferents to the monkey LGN are similar to those identified in the cat. By combining the retrograde transport of tracers injected into the monkey LGN with immunocytochemical labeling for choline acetyl transferase, brain nitric oxide synthase, glutamic acid decarboxylase, tyrosine hydroxylase, or the histochemical nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reaction, we determined that the organization of neurotransmitter inputs to the monkey LGN is strikingly similar to the patterns occurring in the cat. In particular, we found that the monkey LGN receives a significant cholinergic/nitrergic projection from the pedunculopontine tegmentum, gamma-aminobutyric acid (GABA)ergic projections from the thalamic reticular nucleus and pretectum, and a cholinergic projection from the parabigeminal nucleus. The major difference between the innervation of the LGN in the cat and the monkey is the absence of a noradrenergic projection to the monkey LGN. The segregation of the noradrenergic cells and cholinergic cells in the monkey brainstem also differs from the intermingled arrangement found in the cat brainstem. Our findings suggest that studies of basic mechanisms underlying the control of visual information flow through the LGN of the cat may relate directly to similar issues in primates, and ultimately, humans.

NMDAR-1 staining in the lateral geniculate nucleus of normal and visually deprived cats.

In normal adult cats, a monoclonal antibody directed toward the NR-1 subunit of the N-methyl-D-aspartate (NMDA) receptor (Pharmingen, clone 54.1) produced dense cellular and neuropil labeling throughout all layers of the lateral geniculate nucleus (LGN) and adjacent thalamic nuclei, including the thalamic reticular, perigeniculate, medial intralaminar, and ventral lateral geniculate nuclei. Cellular staining revealed well-defined somata, and in some cases proximal dendrites. NMDAR-1 cell labeling was also evident in the LGN of early postnatal kittens, suggesting that developing LGN cells possess this receptor subunit at or before eye opening. Within the A-layers of the adult LGN, staining encompassed a wide range of soma sizes. Soma size comparisons of NMDAR-1 stained cells with those stained with an antibody directed toward a nonphosphorylated neurofilament protein (SMI-32), which selectively stains Y-relay cells (Bickford et al., 1998), or an antibody to glutamic acid decarboxylase (GAD), which stains for GABAergic interneurons, suggested that NMDA receptors are utilized by relay cells and interneurons. NMDAR-1 staining was also observed in the LGN of cats with early monocular lid suture. Although labeling was apparent in both deprived and nondeprived A-layers of LGN, the distribution of soma sizes was significantly different. In the deprived A-layers of LGN, staining was limited to small- and medium-sized cells. Cells with relatively large soma were lacking. However, cell density measurements as well as soma size comparisons with cells stained for Nissl substance suggested these differences were due to deprivation-induced cell shrinkage and not to a loss of NMDAR-1 staining in Y-cells. Taken together, these results suggest that NMDA receptors are utilized by both relay cells and interneurons in LGN and that alterations in early visual experience do not necessarily affect the expression of NMDA receptors in the LGN.

Development of the cholinergic, nitrergic, and GABAergic innervation of the cat dorsal lateral geniculate nucleus.

Cholinergic projections from the brainstem have been shown to be important modulators of visual activity in the dorsal lateral geniculate nucleus (dLGN) of the adult, but little is known about the role of these modulatory inputs during development. We examined the postnatal development of the cholinergic innervation of the dLGN by using an monoclonal antibody against choline acetyl transferase (ChAT). We also investigated the development of GABAergic interneurons in the dLGN by using an antibody against glutamic acid decarboxylase (GAD), and the developmental expression of brain nitric oxide synthase (BNOS) by using an antibody against this enzyme. We found that brainstem cells surrounding the brachium conjunctivum express ChAT at birth, although axons in the dLGN do not express ChAT until the end of the first postnatal week. Cholinergic synaptic contacts were observed as early as the second postnatal week. The number of axons stained with the ChAT antibody increased slowly during the subsequent weeks in the dLGN and reached adult levels by the eighth postnatal week. GABAergic interneurons were present at birth and reached their adult soma size by the third postnatal week. GABAergic fibers are dense at birth but change during development from a diffuse pattern to clustered arrangements that can be recognized as distinct rings of GAD staining by P35. Cellular expression of BNOS was seen within all dLGN laminae during development. The BNOS-stained cells are tentatively identified as interneurons because their soma sizes were similar to those of GAD-stained cells. Although cellular BNOS staining remained robust in the C1-3 laminae through adulthood, cellular expression of BNOS in the A laminae declined during the first five postnatal weeks and remains sparse in the adult. As cellular BNOS staining declined, there was a steady increase in BNOS-stained fibers, which paralleled the increase of ChAT-stained fibers that are known to colocalize BNOS in the adult. Our results emphasize the continued transformations of intrinsic as well as extrinsic innervation patterns that occur during the development, of the dLGN.

The location of muscarinic type 2 receptors within the synaptic circuitry of the cat lateral posterior nucleus.

The ultrastructural distribution of the muscarinic type 2 acetylcholine receptor (M2) was examined in the lateral division of the lateral posterior (LP) nucleus of the cat thalamus, using immunocytochemistry. Postembedding immunocytochemical staining for gamma-aminobutyric acid (GABA) further characterized M2 stained profiles. M2 receptors were predominately found on small caliber (presumably distal) dendritic arbors of thalamocortical cells and interneurons in the lateral LP nucleus. While glomeruli were not abundant in the lateral LP nucleus, occasionally they contained dendritic terminals of interneurons (F2 profiles) stained for M2 receptors. Some GABAergic terminals throughout the neuropil also stained for M2 receptors. The location of M2 receptors correlates well with the cholinergic innervation of the lateral LP nucleus and suggests that muscarinic modulation of visual signals differs in the lateral LP nucleus as compared with the lateral geniculate and pulvinar nuclei.

Growth-associated protein 43 is located in type I corticothalamic terminals in the cat visual thalamus.

Growth-associated protein 43 (GAP 43) is a presynaptic protein that has been proposed to be involved in synaptic plasticity. To determine the location of GAP 43 within the synaptic circuitry of the thalamus, immunocytochemical staining for GAP 43 was examined in a relay nucleus, the dorsal lateral geniculate nucleus (dLGN), and two association nuclei, the pulvinar nucleus and the lateral subdivision of the lateral posterior (LP) nucleus. In the dLGN, moderate neuropil staining was seen in the A laminae, and denser staining was found in the interlaminar zones and the C laminae. Uniform dense staining of the neuropil was found in both the pulvinar and LP nuclei. At the ultrastructural level, the GAP 43 staining was restricted to small-diameter myelinated axons, thin unmyelinated fibers, and small terminals that contained densely packed round vesicles (RS profiles) and made asymmetric synaptic contacts with small-caliber dendrites in the extraglomerular neuropil. The distribution of immunocytochemical label within the visual thalamus suggests that GAP 43 is confined to type I corticothalamic terminals and axons that originate from extrastriate cortical areas. These results also suggest that in both relay and association nuclei GAP 43 may be used to augment the cortical control of thalamic activity. In addition, these results underscore the distinction between the small type I corticothalamic terminals, which appear to contain GAP 43 throughout the visual thalamus, and the large type II corticothalamic terminals that, like the type II retinal terminals in the dLGN, do not contain GAP 43.

Two types of interneurons in the cat visual thalamus are distinguished by morphology, synaptic connections, and nitric oxide synthase content.

The distribution of the neuronal form of the nitric oxide-synthesizing enzyme, brain nitric oxide synthase (BNOS), was examined in the cat thalamus by using immunocytochemical techniques. BNOS was found in both cells and fibers throughout the visual thalamus. BNOS-stained cells were found consistently in the C laminae of the lateral geniculate nucleus (LGN), the pulvinar nucleus, and the lateral posterior nucleus (LP). In the A laminae of the LGN, variable numbers of BNOS-stained cells also could be detected. BNOS-stained cells were identified as a subset of interneurons because they all stained for glutamic acid decarboxylase (GAD), but not all GAD-stained cells contained BNOS. The average soma area of BNOS-stained cells was slightly greater than the average soma area of GAD-stained cells. BNOS-stained cells display a distinctive dendritic morphology, which is consistent with previous descriptions of class V neurons (Updyke [1979] J. Comp. Neurol. 186:603-619); they have widespread but fairly sparse arbors of thin, somewhat beaded dendrites. BNOS-stained cells participate in a distinct synaptic circuitry. Although many GAD-stained profiles are filled with vesicles and participate in complex synaptic arrangements, known as glomeruli, BNOS-stained dendrites contain small clusters of vesicles and form dendrodendritic contacts in the extraglomerular neuropil. Thus, there appear to be at least two types of gamma-aminobutyric acidergic interneurons in the visual thalamus of the cat. Interneurons that do not contain BNOS (class III morphology) may exert their effects primarily within synaptic glomeruli (Hamos et al. [1985] Nature 317:618-621), whereas interneurons that contain BNOS (class V morphology) contribute primarily to the extraglomerular neuropil.

Synaptic targets of cholinergic terminals in the cat lateral posterior nucleus.

We examined profiles in the neuropil of the lateral division of the lateral posterior (LP) nucleus of the cat stained with antibodies against choline acetyl transferase (ChAT) or gamma-aminobutyric acid (GABA), and several differences in the synaptic circuitry of the lateral LP nucleus compared with the pulvinar nucleus and lateral geniculate nucleus (LGN) were identified. In the lateral LP nucleus, there are fewer glomerular arrangements, fewer GABAergic terminals, and fewer cholinergic terminals. Correspondingly, the neuropil of the lateral LP nucleus appears to be composed of a higher percentage of small type I cortical terminals (RS profiles). Similar to the pulvinar nucleus and the LGN, the cholinergic terminals present in the lateral LP nucleus contact both GABA-negative profiles (thalamocortical cells; 74%) and GABA-positive profiles (interneurons; 26%). However, in contrast to the pulvinar nucleus and the LGN, the majority of cholinergic terminals in the lateral LP nucleus contact small-caliber dendritic shafts outside of glomeruli (60 of 82; 73%). Consequently, most cholinergic terminals are in close proximity to RS profiles. Therefore, whereas the cholinergic input to the LGN and pulvinar nucleus appears to be positioned to selectively influence the response of thalamocortical cells to terminals that innervate glomeruli (retinal terminals or large type II cortical terminals), the cholinergic input to the lateral LP nucleus may function primarily in the modulation of responses to terminals that innervate distal dendrites (small type I cortical terminals).

Location of muscarinic type 2 receptors within the synaptic circuitry of the cat visual thalamus.

A cholinergic projection from the parabrachial region (PBR) of the brainstem to the visual thalamus has been studied in great detail during the past 20 years. A number of physiological studies have demonstrated that this projection causes a dramatic change in thalamic activity during the transition from sleep to wakefulness. Additionally, the PBR may mediate more subtle changes in thalamic activity as attentional levels fluctuate during the waking state. The synaptic circuitry underlying these events has been identified in the cat thalamus. However, there is currently no anatomical information regarding the distribution of cholinergic receptors in relation to this circuitry. To begin to understand how the PBR projection modulates thalamic activity, we used immunocytochemical techniques to examine the distribution of muscarinic type 2 (M2) receptors in the visual thalamus of the cat. The distribution of M2 receptors correlates well with previous reports of the distribution of cholinergic terminals in the visual thalamus. At the light microscopic level, dense M2 staining was seen in the neuropil of the dorsal lateral geniculate nucleus (dLGN) and pulvinar nucleus and in somata and proximal dendrites of cells in the thalamic reticular nucleus (TRN). In the dLGN and pulvinar nucleus, we quantitatively analyzed the distribution of M2 receptors using electron microscopy. Postembedding immunocytochemistry for gamma aminobutyric acid (GABA) was used to determine whether M2 receptors are present on interneurons or thalamocortical cells. In particular, we examined the distribution of M2 receptors with respect to the known sites of PBR terminations. The dendrites of both thalamocortical cells and interneurons were stained for the M2 receptors in both the glomerular and extraglomerular neuropil. However, the densest staining was found in glomerular GABAergic profiles that displayed the morphology associated with interneuron dendritic terminals (F2 profiles). Our data suggest that M2 receptors play an important role both in blocking thalamic spindle oscillations and in increasing the efficacy of signal transmission during increased attentional states.

Neurofilament proteins in Y-cells of the cat lateral geniculate nucleus: normal expression and alteration with visual deprivation.

We examined neurofilament staining in the normal and visually deprived lateral geniculate nucleus (LGN), using the SMI-32 antibody. This antibody preferentially stains LGN cells that display the morphological characteristics of Y-cells. The soma sizes of SMI-32-stained cells were consistent with those of the overall population of Y-cells, and the Golgi-like staining of their dendrites revealed a radial distribution that often crossed laminar boundaries. Labeled cells were distributed within the A laminae (primarily near laminar borders), the magnocellular portion of the C laminae, and the medial intralaminar nucleus, but they were absent in the parvocellular C laminae. Electron microscopic examination of SMI-32-stained tissue revealed that staining was confined to somata, dendrites, and large myelinated axons. Retinal synapses on SMI-32-labeled dendrites were primarily simple axodendritic contacts; few triadic arrangements were observed. In the LGN of cats reared with monocular lid suture, SMI-32 staining was decreased significantly in the A laminae that received input from the deprived eye. Dephosphorylation of the tissue did not alter the cellular SMI-32 staining patterns. Analysis of staining patterns in the C laminae and monocular zone of the A laminae suggests that changes in the cytoskeleton after lid suture reflect cell class and not binocular competition. Taken together, the results from normal and lid-sutured animals suggest that the cat LGN offers a unique model system in which the cytoskeleton of one class of cells can be manipulated by altering neuronal activity.

Synaptic targets of cholinergic terminals in the pulvinar nucleus of the cat.

We compared the cholinergic innervation of the pulvinar nucleus, a thalamic association nucleus, to previous studies of the cholinergic innervation of the dorsal lateral geniculate nucleus (dLGN), a thalamic relay nucleus. Both nuclei receive a dense innervation from cholinergic cells of the brainstem parabrachial region (PBR). In the dLGN, PBR terminals are located in close proximity to retinal terminals. Our goal was to determine whether PBR terminals in the pulvinar nucleus are located in close proximity to corticothalamic terminals. We identified PBR terminals with a monoclonal antibody directed against choline acetyltransferase (ChAT). Cholinergic terminals contacted dendrites (142 of 160, or 89%) or vesicle-filled profiles (18 of 160, or 11%). A subset of 55 terminals was stained for gamma-aminobutyric acid (GABA) to determine whether profiles postsynaptic to cholinergic terminals originate from thalamocortical cells (GABA-) or interneurons (GABA+). The majority (44 of 55, or 80%) of postsynaptic profiles were GABA- dendrites. The minority (11 of 55, or 20%) were GABA+ dendrites with vesicles. This distribution of contacts is very similar to that seen in the dLGN. However, the most significant finding was that most cholinergic contacts (121 of 160, or 76%) were located within complex clusters identified as glomeruli. This is the primary site of contacts made by corticothalamic terminals originating from layer V cells. These results suggest that while the PBR enhances retinal signals in the dLGN, it may also enhance cortical signals in the pulvinar nucleus. Thus, activity in the PBR may stimulate both an increased flow of retinal information to visual cortex, as well as an increased flow of information between different visuomotor areas of cortex.

Immunocytochemistry and distribution of parabrachial terminals in the lateral geniculate nucleus of the cat: a comparison with corticogeniculate terminals.

We used immunohistochemistry in cats to demonstrate the presence of brain nitric oxide synthase (BNOS) in cholinergic fibers within the A-laminae of the lateral geniculate nucleus. We used a double labeling procedure with electron microscopy and found that all terminals labeled for choline acetyltransferase (ChAT) in the geniculate A-laminae were double labeled for BNOS. Also, some interneuron dendrites, identified by labeling for gamma-aminobutyric acid (GABA), contained BNOS, but relay cell dendrites did not. We then compared parabrachial and corticogeniculate terminals, identifying the former by BNOS/ChAT labeling and the latter by orthograde transport of biocytin injected into cortical area 17, 18, or 19. All corticogeniculate terminals and most BNOS- or ChAT-positive brainstem terminals displayed RSD morphology, whereas some brainstem terminals exhibited RLD morphology. However, parabrachial terminals were larger, on average, than corticogeniculate terminals. We also found that parabrachial terminals were located both inside and outside of glomeruli, and they always contacted relay cell dendrites proximally among retinal terminals (the retinal recipient zone). In contrast, the cortical terminals were limited to peripheral dendrites (the cortical recipient zone). Thus, little if any overlap exists in the distribution of parabrachial and corticogeniculate terminals on the dendrites of relay cells.

Predicting aggressive and socially disruptive behavior in a maximum security forensic psychiatric hospital.

The predictive utility of Hare, Hart, and Cox's Psychopathy Checklist Screening Version (PCL:SV) was assessed utilizing a sample of forensic psychiatric patients from Vernon State Hospital in Vernon, Texas. A sample of 55 patients were interviewed and rated on the PCL:SV. During a six month follow up, occurrences of self-harm (suicide attempts and self mutilation), aggression (verbal abuse and threats, irritability, belligerence, and fighting) escape potential (threats and attempts), and treatment refusal (medication, tests, and physician's appointments) were rated. Separate stepwise multiple regression analyses were performed utilizing patient's age, type of charges, documented history of alcohol/drug abuse and the PCL:SV as predictor variables. Results indicate that the PCL:SV is predictive of aggression and treatment noncompliance.

Rearing with monocular lid suture induces abnormal NADPH-diaphorase staining in the lateral geniculate nucleus of cats.

We investigated the changes in NADPH-diaphorase staining that occur in the lateral geniculate nucleus of cats following rearing with monocular lid suture. This staining allows visualization of the synthesizing enzyme of nitric oxide, a neuromodulator associated with plasticity. In the lateral geniculate nucleus of normally reared cats, NADPH-diaphorase exclusively labels the axons and terminals of an input from the parabrachial region of the brainstem; no geniculate cells in the A-laminae are labeled. Early monocular lid suture has no obvious effect on the NADPH-diaphorase staining of parabrachial axons. However, this lid suture results in the abnormal appearance of NADPH-diaphorase staining for geniculate somata. These cells are located primarily in the nondeprived laminae. Double-labeling experiments indicate that these cells with abnormal NADPH-diaphorase reactivity are Y relay cells: NADPH-diaphorase staining is found in cells retrogradely labeled from visual cortex; it is found in cells labeled with a monoclonal antibody for CAT-301, which selectively targets Y cells; it is not found in cells labeled with an anti-GABA antibody, which targets interneurons. Also, NADPH-diaphorase labeled cells are among the largest cells in the nondeprived laminae, again suggesting that they are Y relay cells. We cannot suggest a specific mechanism for this induction of NADPH-diaphorase labeling, but it does not seem to be due to abnormal binocular competition induced by the monocular lid suture.