Leslie J. Vogt

Cytology and functionally correlated circuits of human posterior cingulate areas.

Human posterior cingulate cortex (PCC) and retrosplenial cortex (RSC) form the posterior cingulate gyrus, however, monkey connection and human imaging studies suggest that PCC area 23 is not uniform and atlases mislocate RSC. We histologically assessed these regions in 6 postmortem cases, plotted a flat map, and characterized differences in dorsal (d) and ventral (v) area 23. Subsequently, functional connectivity of histologically guided regions of interest (ROI) were assessed in 163 [(18)F]fluorodeoxyglucose human cases with PET. Compared to area d23, area v23 had a higher density and larger pyramids in layers II, IIIc, and Vb and more intermediate neurofilament-expressing neurons in layer Va. Coregisrtration of each case to standard coordinates showed that the ventral branch of the splenial sulci coincided with the border between d/v PCC at -5.4 +/- 0.17 cm from the vertical plane and +1.97 +/- 0.08 cm from the bi-commissural line. Correlation analysis of glucose metabolism using histologically guided ROIs suggested important circuit differences including dorsal and ventral visual stream inputs, interactions between the vPCC and subgenual cingulate cortex, and preferential relations between dPCC and the cingulate motor region. The RSC, in contrast, had restricted correlated activity with pericallosal cortex and thalamus. Visual information may be processed with an orbitofrontal link for synthesis of signals to drive premotor activity through dPCC. Review of the literature in terms of a PCC duality suggests that interactions of dPCC, including area 23d, orient the body in space via the cingulate motor areas, while vPCC interacts with subgenual cortex to process self-relevant emotional and non-emotional information and objects and self-reflection.

Chronic ▵9-Tetrahydrocannabinol Treatment Produces a Time-Dependent Loss of Cannabinoid Receptors and Cannabinoid Receptor-Activated G Proteins in Rat Brain

Abstract : Chronic treatment of rats with ▵9‐tetrahydrocannabinol (▵9‐THC) results in tolerance to its acute behavioral effects. In a previous study, 21‐day ▵9‐THC treatment in rats decreased cannabinoid activation of G proteins in brain, as measured by in vitro autoradiography of guanosine‐5′‐O‐(3‐[35S]thiotriphosphate) ([35S]GTPγS) binding. The present study investigated the time course of changes in cannabinoid‐stimulated [35S]GTPγS binding and cannabinoid receptor binding in both brain sections and membranes, following daily ▵9‐THC treatments for 3, 7, 14, and 21 days. Autoradiographic results showed time‐dependent decreases in WIN 55212‐2‐stimulated [35S]GTPγS and [3H]WIN 55212‐2 binding in cerebellum, hippocampus, caudate‐putamen, and globus pallidus, with regional differences in the rate and magnitude of down‐regulation and desensitization. Membrane binding assays in these regions showed qualitatively similar decreases in WIn 55212‐2‐stimulated [35S]GTPγS binding and cannabinoid receptor binding (using [3H]SR141716A), and demonstrated that decreases in ligand binding were due to decreases in maximal binding values, and not ligand affinities. These results demonstrated that chronic exposure to ▵9‐THC produced time‐dependent and region‐specific down‐regulation and desensitization of brain cannabinoid receptors, which may represent underlying biochemical mechanisms of tolerance to cannabinoids.

Anterior Cingulate Cortex and the Medial Pain System

The processing of sensory afferents in the cerebral cortex involves divergent processing of components of each sensory space. In the visual system, for example, there are separate and sequential, corticocortical projections for the analysis of form, color, movement, and depth (DeYoe and Van Essen, 1988; Livingstone and Hubel, 1988; Zeki and Shipp, 1988). A divergence of functional processing of different features of noci-ceptor-evoked activity may also occur in the cerebral cortex. Thus, there is a long history for dividing the pain system into two theoretical components: one involved in localization and sensory discrimination and the other involved in affective responses to noxious stimuli (e.g., Melzack and Casey, 1968; Melzack, 1975; Kenshalo and Willis, 1991).

Architecture and Neurocytology of Monkey Cingulate Gyrus

Human functional imaging and neurocytology have produced important revisions to the organization of the cingulate gyrus and demonstrate four structure/function regions: anterior, midcingulate (MCC), posterior (PCC), and retrosplenial. This study evaluates the brain of a rhesus and 11 cynomolgus monkeys with Nissl staining and immunohistochemistry for neuron‐specific nuclear binding protein, intermediate neurofilament proteins, and parvalbumin. The MCC region was identified along with its two subdivisions (a24′ and p24′). The transition between areas 24 and 23 does not involve a simple increase in the number of neurons in layer IV but includes an increase in neuron density in layer Va of p24′, a dysgranular layer IV in area 23d, granular area 23, with a neuron‐dense layer Va and area 31. Each area on the dorsal bank of the cingulate gyrus has an extension around the fundus of the cingulate sulcus (f 24c, f 24c′, f 24d, f 23c), whereas most cortex on the dorsal bank is composed of frontal motor areas. The PCC is composed of a dysgranular area 23d, area 23c in the caudal cingulate sulcus, a dorsal cingulate gyral area 23a/b, and a ventral area 23a/b. Finally, a dysgranular transition zone includes both area 23d and retrosplenial area 30. The distribution of areas was plotted onto flat maps to show the extent of each and their relationships to the vertical plane at the anterior commissure, corpus callosum, and cingulate sulcus. This major revision of the architectural organization of monkey cingulate cortex provides a new context for connection studies and for devising models of neuron diseases. J. Comp. Neurol. 485:218–239, 2005.

Chronic Heroin Self-Administration Desensitizes μ Opioid Receptor-Activated G-Proteins in Specific Regions of Rat Brain

In previous studies from our laboratory, chronic noncontingent morphine administration decreased μ opioid receptor-activated G-proteins in specific brainstem nuclei. In the present study, μ opioid receptor binding and receptor-activated G-proteins were examined after chronic heroin self-administration. Rats were trained to self-administer intravenous heroin for up to 39 d, achieving heroin intake up to 366 mg · kg−1 · d−1. μ opioid-stimulated [35S]GTPγS and [3H]naloxone autoradiography were performed in adjacent brain sections. Agonist-stimulated [35S]GTPγS autoradiography also examined other G-protein-coupled receptors, including δ opioid, ORL-1, GABAB, adenosine A1, cannabinoid, and 5-HT1A. In brains from heroin self-administering rats, decreased μ opioid-stimulated [35S]GTPγS binding was observed in periaqueductal gray, locus coeruleus, lateral parabrachial nucleus, and commissural nucleus tractus solitarius, as previously observed in chronic morphine-treated animals. In addition, decreased μ opioid-stimulated [35S]GTPγS binding was found in thalamus and amygdala after heroin self-administration. Despite this decrease in μ-activated G-proteins, [3H]naloxone binding demonstrated increased μ opioid receptor binding in several brain regions after heroin self-administration, and there was a significant decrease in μ receptor G-protein efficiency as expressed as a ratio between agonist-activated G-proteins and μ receptor binding. No effects on agonist-stimulated [35S]GTPγS binding were found for any other receptor examined. The effect of chronic heroin self-administration to decrease μ-stimulated [35S]GTPγS binding varied between regions and was highest in brainstem and lowest in the cortex and striatum. These results not only provide potential neuronal mechanisms that may contribute to opioid tolerance and dependence, but also may explain why various chronic effects of opioids develop to different degrees.

Cytology of Human Caudomedial Cingulate, Retrosplenial, and Caudal Parahippocampal Cortices

Brodmann showed areas 26, 29, 30, 23, and 31 on the human posterior cingulate gyrus without marking sulcal areas. Histologic studies of retrosplenial areas 29 and 30 identify them on the ventral bank of the cingulate gyrus (CGv), whereas standardized atlases show area 30 on the surface of the caudomedial region. This study evaluates all areas on the CGv and caudomedial region with rigorous cytologic criteria in coronal and oblique sections Nissl stained or immunoreacted for neuron‐specific nuclear binding protein and nonphosphorylated neurofilament proteins (NFP‐ir). Ectosplenial area 26 has a granular layer with few large pyramidal neurons below. Lateral area 29 (29l) has a dense granular layer II‐IV and undifferentiated layers V and VI. Medial area 29 (29m) has a layer III of medium and NFP‐ir pyramids and a layer IV with some large, NFP‐ir pyramidal neurons that distinguish it from areas 29l, 30, and 27. Although area 29m is primarily on the CGv, a terminal branch can extend onto the caudomedial lobule. Area 30 is dysgranular with a variable thickness layer IV that is interrupted by large NFP‐ir neurons in layers IIIc and Va. Although area 30 does not appear on the surface of the caudomedial lobule, a terminal branch can form less that 1% of this gyrus. Area 23a is isocortex with a clear layer IV and large, NFP‐ir neurons in layers IIIc and Va. Area 23b is similar to area 23a but with a thicker layer IV, more large neurons in layer Va, and a higher density of NFP‐ir neurons in layer III. The caudomedial gyral surface is composed of areas 23a and 23b and a caudal extension of area 31. Although posterior area 27 and the parasubiculum are similar to rostral levels, posterior area 36′ differs from rostral area 36. Subregional flat maps show that retrosplenial cortex is on the CGv, most of the surface of caudomedial cortex is areas 23a, 23b, and 31, and the retrosplenial/parahippocampal border is at the ventral edge of the splenium. Thus, Brodmanns map understates the rostral extent of retrosplenial cortex, overstates its caudoventral extent, and abridges the caudomedial extent of area 23. J. Comp. Neurol. 438:353–376, 2001.

Multivariate Analysis of Laminar Patterns of Neurodegeneration in Posterior Cingulate Cortex in Alzheimer's Disease

Posterior cingulate cortex is the site of earliest reductions in glucose metabolism and qualitatively different laminar patterns of neurodegeneration in Alzheimers disease (AD). This study used multivariate analyses of area 23 in 72 cases of definite AD to assess relationships between laminar patterns of neurodegeneration, neurofibrillary tangle (NFT) and senile plaque (SP) densities, age of disease onset and duration, and apolipoprotein E (ApoE) genotype. No age-related changes in neurons occurred over four decades in 17 controls and regression analysis of all AD cases showed no relationships between neuron, SP, and tau-immunoreactive NFT densities. Principal components analysis of neurons in layers III-Va and eigenvector projections showed five subgroups. The subgroups were independent because each had a full range of disease durations and qualitatively different laminar patterns in degeneration suggested disease subtypes (ST). Cases with most severe neuron losses (STSevere) had an early onset, most SP, and highest proportion of ApoE epsilon4 homozygotes. Changes in the distribution of NFT were similar over disease course in two subtypes and NFT did not account for most neurodegeneration. In STII-V with moderate neuron loss in most layers, cases with no NFT had a disease duration of 3.5 +/- 0.9 years (mean +/- SEM), those with most in layers IIIc or Va had a duration of 7.3 +/- 1 years, and those with most in layers II-IIIab had a duration of 12.1 +/- 1 years. In STSevere, cases with highest NFT densities in layers II-IIIab also were late stage. Finally, epsilon4 homozygotes were most frequent in STSevere, but four statistical tests showed that this risk is not directly involved in neurodegeneration. In conclusion, multivariate pattern recognition shows that AD is composed of independent neuropathological subtypes and NFT in area 23 do not account for most neuron losses.

Distribution and Properties of Visceral Nociceptive Neurons in Rabbit Cingulate Cortex

&NA; Human imaging localizes most visceral nociceptive responses to anterior cingulate cortex (ACC), however, imaging in conscious subjects cannot completely control anticipatory and reflexive activity or resolve neuron activity. This study overcame these shortcomings by recording individual neuron responses in 12 anesthetized and paralyzed rabbits to define the visceronociceptive response pattern by region and layer. Balloon distension was applied to the colon at innocuous (15 mmHg) or noxious (60 mmHg) intensities, and innocuous and noxious mechanical, thermal and electrical stimuli were applied to the skin. Simultaneous recording from multiple regions assured differences were not due to anesthesia and neuron responses were resolved by spike sorting using principal components analysis. Of the total 346 neurons, 48% were nociceptive; responding to noxious levels of visceral or cutaneous stimulation, or both. Visceronociceptive neurons were most frequent in ACC (39%) and midcingulate cortex (MCC, 36%) and infrequent in retrosplenial cortex (RSC, 12%). In contrast, cutaneous nociceptive units were higher in MCC (MCC, 43%; ACC, 32%; RSC, 23%). Visceral‐specific neurons were proportionately more frequent in ACC (37%), while cutaneous‐specific units predominated in RSC (62.5%). Visceral nociceptive response durations were longer than those for cutaneous responses. Postmortem analysis of electrode tracks confirmed regional designations, and laminar analysis found inhibitory responses mainly in superficial layers and excitatory in deep layers. Thus, cingulate visceral nociception extends beyond ACC, this is the first report of nociceptive activity in RSC including nociceptive cutaneous responses, and these regional differences require a new model of cingulate nociceptive processing.

Norepinephrinergic afferents and cytology of the macaque monkey midline, mediodorsal, and intralaminar thalamic nuclei

The midline and intralaminar thalamic nuclei (MITN), locus coeruleus (LC) and cingulate cortex contain nociceptive neurons. The MITN that project to cingulate cortex have a prominent innervation by norepinephrinergic axons primarily originating from the LC. The hypothesis explored in this study is that MITN neurons that project to cingulate cortex receive a disproportionately high LC input that may modulate nociceptive afferent flow into the forebrain. Ten cynomolgus monkeys were evaluated for dopamine-β hydroxylase (DBH) immunohistochemistry, and nuclei with moderate or high DBH activity were analyzed for intermediate neurofilament proteins, calbindin (CB), and calretinin (CR). Sections of all but DBH were thionin counterstained to assure precise localization in the mediodorsal and MITN, and cytoarchitecture was analyzed with neuron-specific nuclear binding protein. Moderate–high levels of DBH-immunoreactive (ir) axons were generally associated with high densities of CB-ir and CR-ir neurons and low levels of neurofilament proteins. The paraventricular, superior centrolateral, limitans and central nuclei had relatively high and evenly distributed DBH, the magnocellular mediodorsal and paracentral nuclei had moderate DBH-ir, and other nuclei had an even and low level of activity. Some nuclei also have heterogeneities in DBH-ir that raised questions of functional segregation. The anterior multiformis part of the mediodorsal nucleus but not middle and caudal levels had high DBH activity. The posterior parafascicular nucleus (Pf) was heterogeneous with the lateral part having little DBH activity, while its medial division had most DBH-ir axons and its multiformis part had only a small number. These findings suggest that the LC may regulate nociceptive processing in the thalamus. The well established role of cingulate cortex in premotor functions and the projections of Pf and other MITN to the limbic striatum suggests a specific role in mediating motor outflow for the LC-innervated nuclei of the MITN.

Muscarinic Receptor Binding Increases in Anterior Thalamus and Cingulate Cortex during Discriminative Avoidance Learning

Training-induced neuronal activity develops in the mammalian limbic system during discriminative avoidance conditioning. This study explores behaviorally relevant changes in muscarinic ACh receptor binding in 52 rabbits that were trained to one of five stages of conditioned response acquisition. Sixteen naive and 10 animals yoked to criterion performance served as control cases. Upon reaching a particular stage of training, the brains were removed and autoradiographically assayed for 3H-oxotremorine-M binding with 50 nM pirenzepine (OXO-M/PZ) or for 3H-pirenzepine binding in nine limbic thalamic nuclei and cingulate cortex. Specific OXO-M/PZ binding increased in the parvocellular division of the anterodorsal nucleus early in training when the animals were first exposed to pairing of the conditional and unconditional stimuli. Elevated binding in this nucleus was maintained throughout subsequent training. In the parvocellular division of the anteroventral nucleus (AVp), OXO-M/PZ binding progressively increased throughout training, reached a peak at the criterion stage of performance, and returned to control values during extinction sessions. Peak OXO-M/PZ binding in AVp was significantly elevated over that for cases yoked to criterion performance. In the magnocellular division of the anteroventral nucleus (AVm), OXO-M/PZ binding was elevated only during criterion performance of the task, and it was unaltered in any other limbic thalamic nuclei. Specific OXO-M/PZ binding was also elevated in most layers in rostral area 29c when subjects first performed a significant behavioral discrimination. Training-induced alterations in OXO-M/PZ binding in AVp and layer Ia of area 29c were similar and highly correlated.