Astrocytes are important for sprouting in the septohippocampal circuit

Damage to the fimbria-fornix, and separately to the perforant path, leads to distinct and dramatic time-dependent increases in glial fibrillary acidic protein immunoreactivity (GFAP-IR) in specific areas of the hippocampal formation. Specifically, fimbria-fornix lesions resulted in an increase in the GFAP-IR in the pyramidal and oriens area of the CA3 as well as the inner molecular layer of the dentate gyrus. In addition, in the septum ipsilateral to the lesion, there was a rapid and robust increase in GFAP-IR in the dorsal lateral quadrant of the septum, but not in the medial region. Only after 30 days did the GFAP-IR reach the medial septum. Following perforant path lesions, there was a selective increase in GFAP-IR in the outer molecular layer of the dentate gyrus. Most of these changes were transient and had disappeared by 30 days postlesion. We speculate that the increase in GFAP-IR in these target areas is a necessary requirement for the sprouting responses that are observed. This hypothesis is supported by the fact that astrocytes secrete NGF in vitro and that NGF activity increases in these target areas following these same lesions. A mechanism for the selective activation of the astrocytes through the initial activation of microglia and secretion of interleukin-1 is postulated.

Electric activity in the neocortex of freely moving young and aged rats

Electroencephalographic activity of the neocortex was evaluated in young (5-7 months) and aged (26-28 months) rats. All animals in the aged group showed behavioral impairment in a spatial task (water maze). A neocortical electroencephalogram was derived simultaneously from 16 different neocortical locations and was subjected to spectral analysis. The frequency of occurrence and duration of high-voltage spindles was determined in two sessions, each involving a total of 30 min alert immobility. Changes in spectral characteristics and high-voltage spindles in response to scopolamine administration were also evaluated. The power of high-frequency activity (8-20 Hz) was significantly reduced in the aged subjects. This was greatest in the temporo-occipital regions, while no significant changes were seen in the mediofrontal region. Scopolamine resulted in a large power increase in all frequency bands, but the increase in the higher-frequency range (8-20 Hz) was significantly less in the aged group. The incidence of high-voltage spindles was 6 times higher and their total duration was 9 times longer in aged rats, with virtually no overlap with the young group. In young rats, scopolamine increased the incidence and total duration of high-voltage spindles, while it decreased both parameters in the aged subjects. Cholinergic neurons in the nucleus basalis appeared shrunken in the aged animals. These findings demonstrate that reliable electroencephalographic changes are present in the neocortex of the aged rat, and that some of the physiological alterations may be due to the pathological changes in the cholinergic nucleus basalis.

Localization of choline acetyltransferase in perikarya and dendrites within the nuclei of the solitary tracts

Immunocytochemistry was used to establish the cellular localization of choline acetyltransferase [ChAT] throughout the rostrocaudal portions of the nuclei of the solitary tracts [NTS] in rat brain. By light microscopy, two distinct populations of ChAT-positive cells were identified. The first consisted of relatively few, medium-sized neurons located in the caudal one-half of the medial NTS just dorsal to the dorsal motor nucleus of the vagus. The second population of ChAT-labeled neurons was located more anteriorly and surrounded the medial and dorsal borders of the tractus solitarius. These cells were more abundant and smaller diameter than those located more caudally. Thick, non-varicose processes with the light microscopic characteristics of dendrites also were selectively labeled for ChAT. A few of these processes were located near or were continuous with the labeled perikarya of the NTS. However, the vast majority of the immunoreactive processes could be traced from ChAT-labeled perikarya in the ventrally adjacent dorsal motor nucleus of the vagus. These dorsally directed dendrites aborized extensively throughout the NTS, but they were densest in the rostral two-thirds of the nucleus. Caudally, the labeled dendrites coursed horizontally, forming a commissure-like structure between the two vagal motor nuclei. Electron microscopy confirmed the perikaryal and dendritic localization of ChAT in the NTS. The perikarya were characterized by dense peroxidase immunoreactivity throughout the cytoplasm, infolded nuclear membranes, and somatic synapses. The labeled dendritic profiles also were intensely immunoreactive and received synaptic input from unlabeled terminals. The unlabeled afferents to somata and dendrites contained large populations of small clear vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Complex spikes in Purkinje cells of the paravermal part of the anterior lobe of the cat cerebellum during locomotion

1. The temporal pattern of the discharge of complex spikes by Purkinje cells in the paravermal cortex of the cerebellar lobule V b/c has been examined during locomotion in awake cats. 2. The peripheral receptive fields of 138 Purkinje cells were examined using light tactile stimulation. In 91% of these cells, complex spikes were evoked by stimuli applied to the ipsilateral forelimb and of eighty-eight cells examined in most detail, 76% had receptive fields including the paw or wrist. Sixty-six per cent had receptive fields restricted to the paw and/or wrist. 3. Complex spikes were not discharged at rigidly fixed times during the step cycle in any of sixty-nine Purkinje cells which were recorded during locomotion on a moving belt. 4. When the discharges were averaged over many steps the probability of occurrence of complex spikes showed small fluctuations during the course of the step cycle, but these fluctuations were shown not to be statistically significantly different from those which could arise by chance. 5. These findings are inconsistent with previous suggestions (e.g. Armstrong, 1974; Rushmer, Roberts & Augter, 1976) that, during locomotion, the climbing fibres act to signal the occurrence of specific peripheral events, such as foot touch-down or lift-off.

Discharges of interpositus and Purkinje cells of the cat cerebellum during locomotion under different conditions

1. Extracellular microelectrodes were used in free-to-move cats to study the locomotor-related discharges of Purkinje cells in the intermediate part of lobule V of the cerebellar anterior lobe and of neurones in the underlying nucleus interpositus anterior. All cells studied discharged rhythmically during locomotion. 2. The discharges during walking at a speed of 0.5 m/s on a horizontal exercise belt were compared with those during (a) walking at 0.9 m/s (when the duration of the step cycle is shortened considerably and the amplitudes of the locomotor electromyograms (EMGs) recorded from flexor and extensor muscles of the limbs are markedly increased) and (b) during walking at 0.5 m/s with the belt tilted uphill by 30 deg (when step duration is little changed but locomotor EMGs are increased by 70-100%). 3. In each of thirty Purkinje cells the timing of the discharges relative to the forelimb step cycle showed no major difference between the two speeds of walking. Most cells discharged at slightly higher overall rates at the faster walking speed but the increase was usually modest, the average being only 5.6 impulses/s (i.e. an increase of 8%). Peak rates sometimes underwent larger increases but the average was only 11.9 impulses/s (+11%). Changes in minimum rate were generally small (an average increase of 0.3 impulses/s). 4. Among twenty-one interpositus neurones there was only one in which discharge timing relative to the step cycle was different between the two speeds. Like the Purkinje cells, most neurones discharged slightly faster at the higher speed but the average increase was only 5.5 impulses/s (+8.5%). Peak firing rates also usually showed a modest increase (averaging 6.2 impulses/s; +6.5%) while minimum rates were little changed. 5. Among nineteen Purkinje cells compared between walking uphill and on the flat only one showed any major difference in discharge phasing; overall firing rates were on average only 1.3 impulses/s (2%) higher for uphill locomotion. 6. Among twenty-one interpositus neurones discharge phasing differed markedly between walking uphill and on the flat in only two cells. Overall discharge rates were on average slightly higher uphill (by 3.5 impulses/s; 6.7%) and peak rates also usually increased slightly (on average, by 6 impulses/s; 7.7%). Minimum rates were higher, on average, by 1.6 impulses/s (+5%). 7. The findings are discussed in relation to current notions of how the intermediate part of the cerebellum may contribute to movement control and it is concluded that the neurones studies probably make little contribution to determining the vigour of the movements of steady walking.

Cholinergic neurons within the rat hippocampus: response to fimbria-fornix transection

The distribution and morphologic characteristics of choline acetyltransferase (ChAT)-containing neurons were studied throughout the rostrocaudal extent of the rat hippocampus and in a midline area just dorsal to the dorsal hippocampus. Peroxidase reaction product was observed with the aid of immunohistochemical methods and a high-titer polyclonal antibody against ChAT, the acetylcholine biosynthetic enzyme. ChAT-positive cells in the hippocampus were characterized by small, round or oval perikarya with two or more proximal processes. They were located within the caudal and temporal hippocampal formation, predominantly within the subiculum, in the stratum lacunosum moleculare, at the border of the stratum lacunosum moleculare and the stratum radiatum, and in the molecular layer of the dentate gyrus. The cells resembled in morphology the small, bipolar and multipolar neocortical ChAT-immunoreactive cells. In addition to the hippocampus, ChAT-positive neurons were observed caudally in a region just above the dorsal hippocampal commissure and rostrally in the columns of the fornix. These cells were large with an oval perikarya and darkly labeled compared to neurons in the hippocampus. They more closely resembled the ChAT-positive neurons in the midline raphe of the medial septal nucleus. Examination of the rat hippocampus 2 and 8 weeks following unilateral lesioning of the fimbria-fornix and supracallosal striae revealed a sparse innervation of ChAT-positive fibers in the hippocampus ipsilateral to the lesion. ChAT-labeled neurons in the hippocampus did not appear to sprout in response to the lesion. In contrast, ChAT-positive cells in the midline did appear to sprout into the medial dorsal subiculum and dorsal medial hippocampus. We conclude that these two populations of cells are distinct with respect to their response to hippocampal denervation and, furthermore, that this distinction may be attributed to a differential response to nerve growth factor.

Three-dimensional pattern of enkephalin-like immunoreactivity in the caudate nucleus of the cat

Recent anatomical investigations of the mammalian neostriatum have uncovered discrete neurochemical zones characterized by low levels of AChE and high levels of enkephalin-like immunoreactivity (ELI) compared with the surrounding neostriatal tissue. These regions, termed striosomes, which appear as patches in individual sections, have been associated with specific afferent and efferent pathways that differ from those of the surrounding neostriatal tissue. In the present study, the 3-dimensional distribution of these enkephalin-rich compartments in the caudate nucleus of the adult cat was investigated using computer-assisted 3-dimensional reconstruction techniques. Series consisting of coronal, sagittal, and horizontal tissue sections were obtained. In individual sections, discrete patches of intense enkephalin-like immunoreactivity appeared against a lighter-staining background. Three-dimensional reconstructions revealed that these patches overlapped across sections to form a highly inter-connected structure within the head and body of the caudate nucleus. Several structural features were evident in these reconstructions that appeared to be similar across animals. One consistent pattern was the formation of enkephalin-labeled finger-like structures radiating from the ventricular edge diagonally across the width of the nucleus. Smaller crossbridges were seen connecting the fingers, which often resulted in the formation of claws or rings of enkephalin-like immunoreactivity. These elements appear to align across planes to form a lattice-like structure outlining continuous regions of matrix. This structure may provide a basis for the orderly interaction between the patch and matrix compartments.

Morphologic alterations of cholinergic processes in the neocortex of aged rats

In the present study we observed enlarged cholinergic processes in the neocortex of aged Fischer 344 rats. These swollen ChAT-positive profiles appeared either as a single axon enlargement or, in many instances, the bulbous processes coalesced to form grape-like clusters of immunoreactivity. The latter structures looked similar to the immunoreactive profiles observed in the cortex of patients with Alzheimer's disease and in the rat septum following fimbria-fornix transection. Together, these data provide evidence that morphologic changes occur within processes of cholinergic neurons in the aged rat. Moreover, the similarity in appearance between the axonal alterations in the aged rat and in patients with Alzheimer's disease suggests a common pathologic process.

Morphological response of axotomized septal neurons to nerve growth factor

Septal efferent fibers from the neurons in the medial septal nucleus are destroyed by fimbria-fornix aspirative lesion. In the present study we used quantitative morphometric techniques to evaluate the response of these axotomized septal neurons to a constant infusion of nerve growth factor (NGF). By 2 weeks following the lesion, approximately 75% of the cholinergic neurons had degenerated in the untreated rats. The remaining cholinergic neurons showed few signs of the effect of the lesion when stained for a polyclonal antibody to ChAT and examined in 40-micron-thick sections. In 1-micron-thick sections the remaining ChAT-immunoreactive (IR) neurons also appeared no different from the intact ChAT neurons. However, non-ChAT-IR neurons had a shrunken nucleus, while all other morphometric parameters appeared normal. NGF infusion protected most of the ChAT-IR neurons from degenerating. The saved neurons had the same parameters as the undamaged ChAT-IR neurons when examined in either 40-micron- or 1-micron-thick sections. In addition, the shrunken appearance of the non-ChAT-IR neurons' nuclei was avoided by the NGF infusions. Enlarged ChAT-IR processes were evident in the dorsolateral quadrant of the septum following damage to the fimbria-fornix. NGF-infusions prevented the formation of these processes. Instead, in the treated animals the dorsal lateral quadrant contained a dense plexus of fine ChAT-IR varicosities. Taken together these results demonstrate that NGF not only can protect the cholinergic neurons from axotomy-induced degeneration but can also cause the saved neurons to maintain the same morphometric appearance as intact ChAT-IR neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of choline acetyltransferase immunoreactive somata in the feline brainstem: implications for REM sleep generation

In the present study we examined the distribution of cholinergic and catecholaminergic neurons, in the feline brainstem, as defined by choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) immunohistochemistry. In the dorsal tegmentum, ChAT immunoreactive neurons were distributed in the parabrachial area [the pedunculopontine group (PPG)] and along the medial adjacent central gray [the lateral dorsal tegmental group (LDT)]. The cholinergic neurons in the LDT area were larger than those in the PPG. When adjacent tissue sections were labeled with TH we noted extensive overlap between catecholamine and cholinergic neurons in the PPG, suggesting that REM sleep may occur as a result of an interaction between these transmitters in this area rather than the medial pontine reticular formation where no cholinergic or catecholamine neurons were found. Cholinergic neurons were also found in the cranial nerve nuclei and the nucleus ambiguus. The presence of cholinergic neurons in the PPG and LDT suggest that these neurons may play an important role in the generation of some of the tonic and phasic components of REM sleep, such as cortical desynchronization, pontogeniculo occipital waves, and muscle atonia.

Development of cholinergic neurons in the septal/diagonal band complex of the rat

In the present study we employed immunohistochemical techniques using a polyclonal antibody against choline acetyltransferase (ChAT) to determine the distribution and cytological features of cholinergic neurons in the developing septal/diagonal band complex of the rat. ChAT-positive perikarya were first clearly detected in this region on embryonic day 17, although the neurons were faintly labeled and lacked the cytological details found in the adult. After birth we observed a dramatic increase in the intensity of the immunolabeling which continued until postnatal day 23. Thereafter, the ChAT-positive neurons assumed their adult-like characteristics.

Response of septal cholinergic neurons to axotomy

In the present study we employed quantitative morphometric techniques to assay the response of septal cholinergic neurons following unilateral transection of the fimbria/fornix and supracallosal stria. Analysis of 50-micron-thick tissue sections with a Quantimet 920 image analysis system demonstrated a reduction in ChAT immunoreactivity as early as 1 day following denervation. This decrease was associated with a drop in the number of labeled cells ipsilateral to the lesion and a decrease in the area of cholinergic perikarya on the lesioned and nonlesioned side of the septum. The response at 1 day, however, was transient, and at 4 days the number of labeled neurons was not significantly different from controls. By 8 days we observed a dramatic reduction in the number and size of ChAT-positive cells ipsilateral to the lesion and a reduction in the size of cholinergic perikarya on the contralateral (i.e., nonlesioned) side. These values persisted throughout the remainder of the study. To assess more completely the morphologic response of neurons to axotomy than can be determined in 50-micron-thick tissue sections, we embedded the adjacent immunolabeled tissue section in Epon and then serially sectioned it to a thickness of 0.75-1.0 micron. By using this method, we were able to measure the area, length, and width of the cell, the area of the nucleus and nucleolus, and the position of the nucleus (i.e., eccentricity). Measurements were performed on ChAT-labeled and nonlabeled cells. The results of our studies demonstrate that cholinergic and noncholinergic cells responded to axotomy in a characteristic yet different fashion from each other and that this response could be quantitatively assayed. In general, labeled and nonlabeled cells on the lesioned side of the septum shrink in response to denervation. This shrunken state was reflected in measurements of cellular area, length, width, and nuclear area. Moreover, other measurements of cellular morphology (i.e., area of the nucleolus, position of the nucleus) indicate that none of the neuronal populations examined in the present study displayed morphologic evidence of regeneration. Our results indicate a dramatic loss of cholinergic perikarya ipsilateral to the lesion. Moreover, although a few neurons do persist they do so in a shrunken state. These data provide an essential baseline for the second study in this series, which will evaluate the effect of nerve growth factor on the survival of denervated septal neurons.

The cerebellar corticonuclear projection from lobule Vb/c of the cat anterior lobe: a combined electrophysiological and autoradiographic study. II. Projections from the vermis

The present study is an investigation of the efferent pathways from Purkinje cells within particular sagittal zones of the vermal region of the cat cerebellar cortex. A combined electrophysiological/autoradiographic technique was used, in which a small volume (10-120 nl) of 3H-leucine was injected into the centre of a chosen cortical zone after the mediolateral extent of the zone had been delimited electrophysiologically on the basis of its climbing fibre input. Study of the uptake and orthograde transport of labelled material by the Purkinje cells showed that the smallest injections gave rise to injection sites which were restricted to a single zone and to terminal labelling which was very reproducible between cases. Larger injections usually resulted in spread of labelled material to neighbouring zones but the resultant distribution of terminal labelling was nevertheless consistent with that arising from smaller injections. The x zone, which receives climbing fibre input transmitted from the ipsilateral forelimb via a dorsal funiculus spino-olivo-cerebellar pathway (DF-SOCP), was found to project to the junctional region between nucleus fastigius and nucleus interpositus posterior (NIP). The b zone, which lies laterally in the vermis and receives climbing fibre input transmitted from both forelimbs (and both hindlimbs) via a slower conducting SOCP, was found to project, not to the cerebellar nuclei proper, but to the ipsilateral lateral vestibular nucleus. The projection of the third zone within the vermis, the a zone, was not examined but it is generally agreed that this zone projects mainly to nucleus fastigius.

A ladder paradigm for studying skilled and adaptive locomotion in the cat

A circular horizontal ladder is described which is suitable for studying skilled and adaptive locomotion in the cat. Four mechanisms built into the ladder require the animal to adapt its normal walking by making either corrective manoeuvres following an unpredictable disturbance, or anticipatory changes informed by vision. In addition to these features, the ladder incorporates a servo-controlled boom to ensure that the cat is almost completely free of any restraint or drag which might otherwise be imposed by leads carrying foot contact, electromyographic and neuronal signals from the animal to the recording equipment. The apparatus is proving in use to be reliable and easy to operate, and our preliminary results clearly implicate supraspinal motor centres in controlling the skilled and adaptive behaviour which the ladder requires.

The cerebellar corticonuclear projection from lobule Vb/c of the cat anterior lobe: a combined electrophysiological and autoradiographic study. I. Projections from the intermediate region

The present study examines the projection to the cerebellar nuclei of Purkinje cells in particular sagittal zones within the intermediate region of the cerebellar cortex. The boundaries between the zones were delimited electrophysiologically on the basis of their climbing fibre input so that a small volume (10-120 nl) of 3H-leucine could be injected into the centre of a chosen zone. The subsequent uptake and orthograde transport of labelled material by the Purkinje cells was studied autoradiographically. It was found that the smallest injections resulted in injection sites restricted to a single cortical zone and extremely reproducible results could be obtained using such a combined electrophysiological/autoradiographic technique. Larger injections sometimes spread to a neighbouring zone but the resultant terminal labelling within the deep nuclei was invariably consistent with the results obtained from smaller injections. The c1 and c3 olivocerebellar zones, which are known to receive climbing fibre input transmitted from the ipsilateral forelimb via a dorsal funiculus spino-olivo-cerebellar pathway (DF-SOCP), were found to project to partially overlapping regions within nucleus interpositus anterior (NIA). No projection to nucleus interpositus posterior (NIP) was demonstrated for either zone. No distinction could be seen between the terminal fields for the medial and lateral halves of the c1 zone which are, however, known to receive their climbing fibre input from quite separate regions within the inferior olive. The c2 zone, which was delimited on the basis of its climbing fibre input which is transmitted from both forelimbs via a lateral funiculus SOCP, was found to project exclusively to interpositus posterior. The hemispheral d1 zone was found to project to the transitional region where interpositus anterior and the dentate nucleus adjoin.

Complex spikes in Purkinje cells in the lateral vermis (b zone) of the cat cerebellum during locomotion

1. Complex spikes (c.s.s) due to climbing fibre input were recorded from forty-one Purkinje cells in the lateral part of the vermis (i.e. the b zone) of lobule V of the cerebellum in cats walking on a moving belt or a horizontal ladder. Most cells were near the tips of the folia making up the lobule and some were shown by antidromic invasion to project to the ipsilateral lateral vestibular nucleus. In all cells c.s.s. could be evoked through mechanical stimuli delivered manually to the neck and/or trunk and/or the limb girdles and/or the proximal parts of the limbs. 2. During walking c.s.s. occurred at rates which ranged in different cells from 0.8 to 2.55/s (i.e. ca. 0.8 to 2/step). When activity was averaged across many successive steps the probability of c.s. occurrence was never completely constant throughout the step cycle, but no tendency was detected for c.s.s to recur at any precisely fixed time during the cycle. 3. When ladder locomotion was perturbed because a rung underwent an unexpected 2 cm descent when stepped on, some cells generated a c.s. at short latency in a proportion of trials. Such responses were well time-locked to the onset of rung movement but not to its cessation (which they often preceded). 4. For perturbations of either forelimb the earliest displacement-related c.s. occurred in different cells between 40 and 64 ms after the onset of rung movement. In different cells c.s.s occurred in from one out of five to three out of four perturbed steps (mean ca. two out of five steps). Eight out of seventeen cells responded to perturbation of the forelimb ipsilateral to the cell and five out of ten responded to contralateral perturbations. 5. Perturbation of the ipsilateral hind limb was accompanied by c.s.s in four out of nine cells and latency was usually longer (by ca. 30-40 ms). One cell showed a decrease in the probability of c.s. occurrence. Insufficient data were obtained for a systematic study of responsiveness to perturbation of the contralateral hind limb. 6. Cells showed different patterns of limb specificity, responding to perturbation of one, two or all of the three limbs studied. In total, c.s.s accompanied perturbation of at least one limb in thirteen out of twenty cells studied (65%).(ABSTRACT TRUNCATED AT 400 WORDS)

Relation of pontine choline acetyltransferase immunoreactive neurons with cells which increase discharge during REM sleep

The purpose of this study was to determine whether neurons in the medial pontine reticular formation with high discharge rates during REM sleep could be localized in regions of the brainstem having neurons displaying choline acetyltransferase immunoreactivity. Six cats were implanted with sleep recording electrodes and microwires to record extracellular potentials of neurons in the pontine reticular formation. Single-units with a S:N ratio greater than 2:1 were recorded for at least two REM sleep cycles. A total of 49 units was recorded from the pontine reticular formation at medial-lateral planes ranging from 0.8 to 3.7 mm. The greatest proportion of the units (28.6%) showed highest discharge during active waking and phasic REM sleep compared to quiet waking, non-REM sleep, transition into REM sleep or quiet REM sleep periods. A percentage (20.4%) of the cells had high discharge associated with phasic REM sleep periods while 8.2% of the cells showed a progressive increase in discharge from waking to REM sleep. Subsequent examination of the distribution of choline acetyltransferase immunoreactive cells in the PRF revealed that cells showing high discharge during REM sleep were not localized near presumed cholinergic neurons. Indeed, we did not find any ChAT immunoreactive somata in the medial PRF, an area which has traditionally been implicated in the generation of REM sleep. These results suggest that while increased discharge of PRF cells may be instrumental to REM sleep generation, these cells are not cholinergic.

An immunohistochemical quantification of fibrous astrocytes in the aging human cerebral cortex

In order to determine whether cortical fibrous astrocytes increase with age, we studied 25 patients ranging in age from 24 to 100 years with no clinical or pathological evidence of dementia or other cerebral disorder. Paraffin sections of mid-frontal cortex were obtained and stained with the avidin-biotin immunolabeling procedure for glial intermediate filament protein. The resulting immunolabeled fibrous astrocytes were then counted in the molecular and cellular (cortical laminae 2-6) layers. Populations of fibrous astrocytes in both layers varied widely among individuals, and in the molecular layer their numbers were not significantly correlated with advancing age. In the cellular layer, however, despite widely ranging cell counts among individuals within the same decades of life, there was a significant linear increase with age. Our data suggest that the increase occurs or accelerates significantly after age 70, but the case numbers preclude reaching such a conclusion with statistical confidence. However, when the patients are divided into those less than 70 and those older, fibrous astrocytes in the cellular layer are shown to be significantly increased in the latter group compared to the former.

Choline acetyltransferase immunoreactivity in neuritic plaques of Alzheimer brain

We have observed dystrophic choline acetyltransferase (ChAT)-positive processes surrounding the amyloid core of neuritic plaques in human neocortex, amygdala and hippocampus, using a polyclonal anti-human ChAT antiserum. These data, and those from studies of the aged monkey by other investigators, provide a morphologic counterpart for the biochemical abnormality of the cholinergic system in Alzheimer's disease and senile dementia of the Alzheimer type.

Professional behavior in collaborative practice

Cost containment, increased severity of illness, earlier patient discharge, and high staff turnover are causing nurse executives to implement new systems of health care delivery. One such delivery system, collaborative practice, strives to maximize efficient and effective use of staff, to improve nurse retention, and to enhance patient care. The authors present one approach to implementing collaborative practice and the empirical findings related to the system's impact on physician-nurse professionalism.

Ultrastructural characterization of choline acetyltransferase-containing neurons in the basal forebrain of rat: evidence for a cholinergic innervation of intracerebral blood vessels

The ultrastructural morphology and vascular associations of cholinergic neurons in the horizontal limb of the nucleus of the diagonal band of Broca (nDBBhl) and amygdala of rat were determined by the immunocytochemical localization of choline acetyltransferase (ChAT), the acetylcholine biosynthetic enzyme. Within the nDBBhl peroxidase reaction product was distributed throughout the cytoplasm of selectively labeled neuronal perikarya and dendrites. Labeled perikarya were characterized by an oval cell body (7-10 microns X 17-26 microns in diameter) in which was located a large nucleus and often a prominent nucleolus. Dendrites were by far the most numerous immuno-labeled profiles in the nDBBhl. The labeled dendrites had a cross-sectional diameter of 0.4-4.6 microns and contained numerous mitochondria and microtubules. Approximately 10% of all immunolabeled dendrites received synaptic contacts from unlabeled presynaptic boutons. In contrast to the relatively large number of ChAT-labeled dendrites within the nDBBhl, ChAT-positive axons were less frequently observed and immunolabeled axon terminals were never detected. The labeled axons had an outside diameter of 0.4-1.4 micron and were myelinated. The absence or relative paucity of immunolabeled terminals in the nDBBhl indicates that most if not all of the cholinergic perikarya within this nucleus are efferent projection neurons. The nDBB is known to have widespread projections to many areas of the neocortex, hippocampus, and amygdala. In the present study we examined the amygdala and observed many ChAT-labeled axon boutons. The immunolabeled varicosities contained numerous agranular vesicles and although ChAT-positive terminals were in direct contact with unlabeled neuronal elements within the amygdala, few if any synaptic densities were detected in a single plane of section. With respect to the vasculature, immunolabeled perikarya and dendrites within the nDBBhl and axon terminals in the amygdala were often in direct apposition to blood vessels. In many instances the labeled profile was observed lying directly on the basal lamina of a capillary endothelial cell. In no instance, however, were membrane densities observed. The presence of cholinergic neuronal elements contacting the vessel wall provides morphologic evidence suggesting that the neurogenic control of cerebral vasculature is in part mediated via a cholinergic mechanism.

The distribution of choline acetyltransferase in the rat amygdaloid complex and adjacent cortical areas, as determined by quantitative micro-assay and immunohistochemistry

The distribution of choline acetyltransferase (ChAT) within the amygdaloid complex has been studied to evaluate what should primarily represent the terminal field of the cholinergic projection from the basal forebrain. Two currently available methods have been combined for the comparison: immunohistochemistry with a monoclonal antibody against ChAT, by a double peroxidase-antiperoxidase procedure, and quantitative histochemistry involving micro-assay of the ChAT activity of contiguous microdissected samples. Both methods indicate prominent ChAT activity in the basolateral amygdaloid nucleus (especially rostrally), the nucleus of the lateral olfactory tract (especially layer II), and the amygdalohippocampal area. Regions of lower ChAT activity were not accurately represented by the immunohistochemistry, but could be discriminated by the quantitative assays. Lowest activity was found in the medial nucleus of the amygdala. Most other regions had activities at least as high as average brain or neocortex. Gradients of enzyme activity were found within several regions, including the basolateral and lateral amygdaloid nuclei and the nearby posterior piriform cortex. In the piriform cortex, a region of particularly high ChAT activity was found at its medial edge near the nucleus of the lateral olfactory tract. The immunohistochemical method shows a few intensely reactive somata in layer III within this zone. Comparison of the results seen with immunohistochemistry and quantitative histochemistry suggests an advantage in using them together, since their respective strengths and weaknesses tend to complement each other.