Cholinergic neurons in the rat cerebral cortex demonstrated by immunohistochemical localization of choline acetyltransferase

The development of cholinergic neurons

Motoneuron precursors acquire some principles of their spatial organization early in their cell lineage, probably at the blastula stage. A predisposition to the cholinergic phenotype in motoneurons and some neural crest cells is detectable at the gastrula to neurula stages. Cholinergic expression is evident upon cessation of cell division. Cholinergic neurons can synthesize ACh during their migration and release ACh from their growth cones prior to target contact or synapse formation. Neurons of different cell lineages can express the cholinergic phenotype, suggesting the importance of secondary induction. Early cholinergic commitment can be modified or reversed until later in development when it is amplified during interaction with target. Motoneurons extend their axons and actively sort out in response to local environmental cues to make highly specific connections with appropriate muscles. The essential elements of the matching mechanism are not species-specific. A certain degree of topographic matching is present throughout the nervous system. In dissociated cell culture, most topographic specificity is lost due to disruption of local environmental cues. Functional cholinergic transmission occurs within minutes of contact between the growth cone and a receptive target. These early contacts contain a few clear vesicles but lack typical ultrastructural specializations and are physiologically immature. An initial stabilization of the nerve terminal with a postsynaptic AChR cluster is not prevented by blocking ACh synthesis, electrical activity, or ACh receptors, but AChR clusters are not induced by non-cholinergic neurons. After initial synaptic contact, there is increasing deposition of presynaptic active zones and synaptic vesicles, extracellular basal lamina and AChE, and postjunctional ridges over a period of days to weeks. There is a concomitant increase in m.e.p.p. frequency, mean quantal content, metabolic stabilization of AChRs, and maturation of single channel properties. At the onset of synaptic transmission, cell death begins to reduce the innervating population of neurons by about half over a period of several days. If target tissue is removed, almost all neurons die. If competing neurons are removed or additional target is provided, cell death is reduced in the remaining population. Pre- or postsynaptic blockade of neuromuscular transmission postpones cell death until function returns.(ABSTRACT TRUNCATED AT 400 WORDS)

Cingulate cell discharge patterns related to hippocampal EEG and their modulation by muscarinic and nicotinic agents

Surface to depth recordings of slow wave theta activity were made through the posterior cingulate cortex (area 29). In other experiments the discharge patterns of neurons located throughout this region were recorded during the occurrence of large amplitude irregular activity (LIA) and slow wave theta activity (type 2) in the hippocampal formation of the urethane-anesthetized rat. The response of these neurons to the systemic administration of the cholinergic agonists, eserine and nicotine, was also tested. The majority of cells (80%) related to hippocampal EEG states were classified as tonic theta-on cells (non-rhythmic). These cells increased their discharge rates significantly, when the slow wave activity in the hippocampus changed from LIA to theta. The administration of eserine and nicotine induced slow wave theta in the hippocampus accompanied by the increased discharge rate of tonic theta-on cingulate cells. The excitatory action of nicotine on the discharges of tonic theta-on cingulate cortical cells is in direct contrast to its inhibitory action on phasic and tonic hippocampal theta-on cell discharges. The observation that phase reversals did not occur in area 29, together with the low incidence of phasic (rhythmic) theta-on cells, suggests that the posterior cingulate cortex does not independently generate type 2 theta. Possible significance of these findings for the interactive functioning of the hippocampal formation and posterior cingulate cortex is discussed.

Cholinergic neurons in the brain of a teleost fish (Porichthys notatus) located with a monoclonal antibody to choline acetyltransferase

A monoclonal antibody (Ab8) to choline acetyltransferase (ChAT) was used to locate structures showing ChAT-like immunoreactivity (ChAT-IR) in the brain of a teleost fish, the midshipman (Porichthys notatus). ChAT is the synthetic enzyme for acetylcholine found in neurons using that neurotransmitter; thus ChAT-IR may be interpreted as indicating putative cholinergic activity. Robust staining is seen in all cranial nerve motor nuclei. In addition, the brainstem of Porichthys is distinguished by two other expansive ChAT-IR zones: a sonic motor nucleus, which innervates swimbladder "drum" muscles, and an octavolateralis efferent nucleus, which innervates acoustic, vestibular, and lateral line end organs. Scattered labeled cells are found in several cranial sensory nuclei--the vagal lobe, and the main and descending trigeminal nuclei. ChAT-IR cells form restricted subpopulations in other noncranial nerve nuclei, including the granule cell layer of the cerebellum; superior, medial, and inferior divisions of the reticular formation; the stratum periventriculare of the midbrain's optic tectum; and the nucleus isthmi in the midbrain tegmentum. In the telencephalon, a dense population of ChAT-IR cells is found in the ventral nucleus of area ventralis; terminals and fine fibers are found in the dorsal, medial, and central nuclei of area dorsalis. Together, the data represent the first complete report of ChAT-IR cell bodies in the brain of any nonmammal with the monoclonal antibody Ab8, which has already been extensively used on a variety of vertebrate brains. The results are thus discussed from a comparative viewpoint, considering reports of ChAT-IR in different taxa.

Acetylcholinesterase in the human frontal associative cortex during the period of cognitive development: early laminar shifts and late innervation of pyramidal neurons

Laminar preferences in fibrillar acetylcholinesterase (AChE) staining change dramatically in the human frontal cortex during the first postnatal year and perikaryal reactivity is found only in non-pyramidal neurons. The AChE reactivity of layer III pyramidal cell bodies and surrounding fibrillar network begins to develop after the first postnatal year, increases gradually and reaches its peak intensity in young adults, displaying a cluster-like arrangement. These data suggest that AChE-rich elements participate in the innervation of cortical associative neurons and layers during the cognitive development in man.

GABA-immunoreactive synaptic boutons in the rat basal forebrain: comparison of neurons that project to the neocortex with pallidosubthalamic neurons

Although the basal forebrain, including the globus pallidus, contains a high concentration of gamma-aminobutyric acid (GABA), it is not known whether all types of neuron in the globus pallidus receive GABAergic synaptic input. We have studied two types of neuron: typical pallidal neurons that project to the subthalamic nucleus and magnocellular neurons which are found in the medial and ventral borders of the globus and project to the sensorimotor cortex. The postembedding immunogold staining of endogenous GABA revealed many preterminal axons and synaptic boutons that contained GABA immunoreactivity. Neurons that projected to the neocortex were postsynaptic to some of the GABA-immunoreactive boutons, the majority of which formed symmetrical membrane specializations. From a series of random electron micrographs through the perikarya and proximal dendrites of such retrogradely labelled neurons the density of GABA-containing afferent synaptic boutons was estimated to be 0.58 GABA-containing boutons per 100 micron of neuronal membrane. The GABA-containing boutons accounted for 72% of the total afferent input in the proximal regions of the pallidocortical neurons examined. The pallidosubthalamic neurons received many more afferent boutons than did the cortically projecting neurons, a high proportion (80.4%) of which were immunoreactive for GABA. The density of GABA-containing boutons in contact with pallidosubthalamic neurons was 8.9 boutons per 100 micron. It is concluded that cortically projecting basal forebrain neurons, that are probably cholinergic, are innervated by GABA-containing afferent boutons. However, pallidosubthalamic neurons in the same part of the basal forebrain are much more densely innervated by GABA-containing boutons.

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)

Neuronal and endothelial sites of acetylcholine synthesis and release associated with microvessels in rat cerebral cortex: ultrastructural and neurochemical studies

We sought to establish what proportion of the cholinergic innervation of the cerebral cortex (CX) is associated with intraparenchymal blood vessels by using immunocytochemical and neurochemical techniques, and whether [3H]acetylcholine ([3H]ACh) is synthesized and released by elements associated with cortical microvessels (MV). MVs and, for comparison, tissue homogenates were prepared using sucrose gradient/differential ultracentrifugation methods. Efficacy of the separation technique was indicated by the activity of gamma-glutamyltranspeptidase (up to 29.2-fold enrichment), an endothelial cell marker enzyme, in the MV fraction and microscopy. The size of isolated microvessels ranged from 5 to 40 micron (o.d.) with 67.7% of the vessels less than 10 micron and 32.2% between 11 and 40 micron (690 vessels measured from 4 animals). By electron microscopy immunoreactive choline acetyltransferase (ChAT), the biosynthetic enzyme for ACh, was localized to: (a) axons and axon terminals opposed to the basal laminae of capillaries and small arterioles, and (b) capillary endothelial cells. ChAT-labeled elements associated with MVs were most prominent in layers I, III and V of the CX consistent with the local pattern of cholinergic innervation. The absolute amount of ACh synthesized (pmol Ach/100 mg wet wt.) by elements associated with cortical MVs was relatively small (2.3% total cortical homogenate activity). Inhibition of MV ChAT activity to 5% of control by the specific ChAT inhibitor, 4-naphthylvinylpyridine, and HPLC analysis of the product, indicated that authentic ACh was measured. Other tissues similarly synthesized small amounts of ACh relative to the CX, caudate nucleus (CN, 2.4%), cerebellum (CRB, 1.4%) and liver (LIV, 3.9%). Consistent with the known extent of the cholinergic innervation of the tissues examined, the rank order of ChAT associated for both MVs and homogenate were: CN greater than CX much greater than CRB greater than LIV. However, based on the specific activities of ChAT, cortical MVs have the remarkable capacity to synthesize ACh at rates 95% greater than cortical (S1 fraction) homogenate (59.0 +/- 3.5 nmol/mg protein/40 min; n = 7), which is enriched in nerve terminals. Except for LV (+11%), other tissues also had remarkably high ChAT activity in MV (% above corresponding homogenate; P less than 0.05, n = 5): CN (+269) and CRB (+313). Release of [3H]ACh from MVs and, for comparison, nerve terminals were graded to K+ depolarization stimulus (5-55 mM), maximal with 55 mM K+ and Ca2+ dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Visualisation of CGRP and ChAT-like immunoreactivity in identified trigeminal neurones by combined peroxidase and alkaline phosphatase enzymatic reactions

We report here a method that allows simultaneous visualisation of two antigens within single neurones. In essence this involves the combined use of horseradish peroxidase and alkaline phosphatase reactions to visualise two markers. Using this method we show that ChAT-and CGRP-like immunoreactivity can be co-localised within single neurones of the V to VII motor nuclei. In the case of the V motor nucleus, we show that each marker can be localised in motoneurones labelled with horseradish peroxidase.

Immunohistochemical conditions for staining choline acetyltransferase-containing axon terminals in the rat

Immunohistochemical conditions for staining cholinergic axon terminals using a commercially available anticholine acetyltransferase (anti-ChAT) monoclonal antibody were determined in the rat. A number of variations of procedures including fixative composition, fixation time, and incubation time and temperature in the anti-ChAT antibody solution were tested. Optimal procedures for minimizing the chance of negative staining of ChAT-containing axon terminals consisted of perfusion with a mixture of 4% paraformaldehyde and 0.2% glutaraldehyde for 3 min followed by a fixative containing only 4% paraformaldehyde for 10 min, and reaction with the anti-ChAT antibody for 2 days at 37 C. The distribution patterns of axon terminals stained in the cerebral cortex and the hippocampal formation were comparable to those reported by other investigators using different monoclonal antibodies.

An anatomical study of cholinergic innervation in rat cerebral cortex

The cholinergic innervation of rat cerebral cortex was studied by immunohistochemical localization of choline acetyltransferase. Stained bipolar cells, fibers and terminals were found in all areas of cortex. The density of cholinergic terminals was similar in all cortical areas with the exception of entorhinal and olfactory cortex, which showed a marked increase in the number of stained terminals. A laminar distribution of cholinergic terminals was found in many cortical areas. In motor and most sensory areas, terminal density was high in layer 1 and upper layer 5, and lowest in layer 4. Visual cortex, in contrast to other cortical areas, was characterized by a dense band of innervation in layer 4. It has been known that the majority of cortical cholinergic structures derive from a projection to cortex from large, multipolar neurons in the basal forebrain, which stain heavily for choline acetyltransferase. In this study, stained fibers were observed to take three different pathways from basal forebrain to cortex. The first, confined to medial aspects of forebrain and cortex, was observed to originate in the septal area, from where fibers formed a discrete bundle, swinging forward around the rostral end of the corpus callosum, then travelling caudally in the cingulate bundle. The second was found to consist of fibers fanning out laterally from the area of the globus pallidus, travelling through the caudate, then continuing for various distances in the corpus callosum before finally turning into the cortex. A third pathway appeared to innervate olfactory and entorhinal cortex. Ibotenic acid injections were made in the area of the globus pallidus to study the effect of lesioning the lateral pathway on the cholinergic innervation in cortex. A major loss of choline acetyltransferase positive terminals was observed in neocortex, but retrosplenial, cingulate, entorhinal and olfactory cortex showed a normal density of cholinergic innervation. The borders separating areas with lesioned cholinergic input from non-lesioned areas were precise. The distribution of stained terminals remaining in cortical areas with lesioned basal forebrain innervation suggests that the basal forebrain projection to cerebral cortex, and not the intrinsic cortical cholinergic neurons, give rise to the laminar distribution of cholinergic terminals observed in normal cortex. To compare the relative densities of different cholinergic cortical systems, the distribution of choline acetyltransferase staining was compared with that of vasoactive intestinal polypeptide and substance P, which are co-localized in some choline acetyltransferase-positive neurons innervating cortex.

A comparison of the localization of choline acetyltransferase and glutamate decarboxylase immunoreactivity in rat cerebral cortex

The neurotransmitter-synthesizing enzymes choline acetyltransferase and glutamate decarboxylase were localized immunocytochemically at the light microscopic level. Their respective laminar distributions were compared in 17 different cytoarchitectural areas, comprising limbic and neocortical regions of rat cerebral cortex. The immunoreactive intensities within these areas were measured with an image analysis system and dark-field optics. Choline acetyltransferase and glutamate decarboxylase immunoreactivity displayed distinctive distribution patterns throughout the cerebrum. In general, limbic cortex showed greater intensity of both choline acetyltransferase and glutamate decarboxylase immunoreactivity than neocortex. For example, choline acetyltransferase immunoreactivity in pyriform and retrosplenial cortex was 54% and 29% greater, respectively, than in neocortex, and glutamate decarboxylase immunoreactivity in the same cortical areas was 5% and 17% greater, respectively. In addition to these regional differences, the marked variations of choline acetyltransferase and glutamate decarboxylase immunostaining were characterized as either coincidental or complementary when comparing their laminar distributions. The laminar pattern and relative intensities of choline acetyltransferase and glutamate decarboxylase immunostaining were coincident in some layers of all cortical regions. For example, both choline acetyltransferase and glutamate decarboxylase immunoreactive intensities were high in cellular layers II and IV of the entorhinal cortex. In contrast, examples of complementary choline acetyltransferase and glutamate decarboxylase immunoreactive patterns were observed in retrosplenial cortex and neocortex. In neocortex, layers III and part of V were intensely glutamate decarboxylase-positive, whereas these same layers were less intensely choline acetyltransferase immunoreactive than the intervening layer IV and upper part of V. Quantitatively, choline acetyltransferase immunoreactivity in layers IV and upper V was 27-37% greater than adjacent layers II and deep V. The glutamate decarboxylase immunostaining pattern was complementary in that layer IV was 19-23% less intensely stained than adjacent layers III and V. Our results demonstrate that terminals immunoreactive for choline acetyltransferase and glutamate decarboxylase, and presumably the synaptic terminals that respectively use acetylcholine or gamma-aminobutyric acid as their neurotransmitters, are distributed in distinct laminar patterns that are strategically situated for modulating either afferent information in the case of cholinergic terminals or efferent transmission for GABAergic endings.(ABSTRACT TRUNCATED AT 400 WORDS)

Choline acetyltransferase immunopositive pyramidal neurons in the rat frontal cortex

The putative cholinergic neurons of the rat's frontal cortex (Krieg's area 10) were studied using monoclonal antibody to choline acetyltransferase (ChAT). This paper reports two novel findings which might be very important to reason the function of the frontal cortex. Firstly, the immunopositive cells were distributed in layers II, IV, V and VI around the rostral half, and layers IV, V and VI around the caudal half of Krieg's area 10. Secondly, the majority of immunopositive neurons in layer V was pyramidal cell.

Immunohistochemistry of choline acetyltransferase in the guinea pig brain

Choline acetyltransferase (ChAT) was localized immunohistochemically within the brain of the guinea pig using a monoclonal antibody. ChAT was found in the cytoplasm of cell bodies and primary dendrites of neurons located in striatum, basal forebrain, cranial nerve motor nuclei and scattered cells in the pons. The greatest numbers of immunoreactive neurons were located in the diagonal band of Broca, medial septum and striatum. Distinct immunoreactive fibers were not visible using this antibody, although a diffuse immunostaining was present in the same nuclear regions as well as in the nerve roots of cranial nerve nuclei and the interpeduncular nuclei. Results of the present study agree closely with other previous reports of acetylcholine distributions.

Observations on choline acetyltransferase containing structures in the CD-1 mouse brain

Central cholinergic structures within the CD-1 mouse were evaluated by immunohistochemical visualization of choline acetyltransferase (ChAT) using the monoclonal antibody AB8. Rostrally, cholinergic neurons were seen within the neostriatum, medial septal nucleus (Ch1), ventral (Ch2) and horizontal (Ch3) limb nuclei and nucleus basalis-substantia innominata complex (Ch4). Caudally, cholinergic neurons were seen in the cuneiformis-pedunculopontine nuclei (Ch5), lateral dorsal tegmental (Ch6) and parabigeminal (Ch8) nuclei as well as the medial habenular nucleus and cranial motor nuclei. Additional cholinergic perikarya were found in the hippocampus and cerebral cortex. ChAT stained fibers were observed in the cerebral cortex and in many fiber fascicles.

Coexistence of GABA- and choline acetyltransferase (ChAT)-like immunoreactivity in the hypoglossal nucleus of the rat

Single and sequential double immunocytochemical techniques were applied to localize gamma-aminobutyric acid (GABA)- and choline acetyltransferase (ChAT)- like immunoreactivity (-LI) in the hypoglossal nucleus of the rat. After subsequential double staining a relatively high number of hypoglossal motor neurons showed the coexistence of both ChAT- and GABA-LI. Coexistence of both substances was also revealed in the axons of the hypoglossal nerve situated within the medulla oblongata. Cells showing only ChAT- or GABA-LI were also observed. Differences in immunostaining between the different cell groups of the hypoglossal nucleus were established. Following axotomy of the right hypoglossal nerve, a decrease or loss of the immunoreactivity for both ChAT and GABA in the motor neurons was established until the 3rd week after the operation. The results obtained do not give evidence on the origin of the GABA-like immunoreactive material and its functional significance in the cholinergic neurons. It can be only speculated that the GABA-like material is either taken up from the intercellular space or is synthesized by the ChAT-LI nerve cells. Functionally, the importance of GABA for the synthesis of gamma-hydroxybutyrate (a novel neurotransmitter candidate) and its postsynaptic transmitter action or presynaptic regulatory action (through autoreceptors in the membrane of the nerve endings) on the release of acetylcholine (ACh) should be taken into consideration.

Choline acetyltransferase-immunoreactive neurons in fetal monkey cerebral cortex

Two monoclonal antibodies to choline acetyltransferase (ChAT) were used to stain the cerebral cortex of fetal monkeys at 110-150 days post-conception. In addition to a small number of immunostained fibers, cells resembling typical non-pyramidal neurons were immunostained in developing layers V and VI and in the subjacent white matter of each area examined (sensory-motor and visual areas). ChAT-immunoreactive neurons have not been described in the cerebral cortex of adult primates, but the present observations indicate such neurons exist in the developing primate cortex.

Descending projections of the basal forebrain in the rat demonstrated by the anterograde neural tracer Phaseolus vulgaris leucoagglutinin (PHA-L)

Descending pathways from the mediobasal forebrain were studied in the rat by injecting anterograde axonal tracer Phaseolus vulgaris leucoagglutinin into the substantia innominata and diagonal band of Broca. From both areas, positive fibers which varied in density were observed in the mediodorsal and ventral parts of the ventroposterior and ventromedial thalamic nuclei, the lateral habenula, the stria medullaris, the lateral hypothalamus and the ventral tegmental area. This descending complex appeared predominantly course through the medial forebrain bundle from which positive fibers ramified into the fasciculus thalamicus to distribute in the thalamic nuclei. A minor descending pathway through the stria medullaris was also noted which terminated in the lateral habenula and the mediodorsal thalamic nucleus. An obvious difference in terminal distribution in the medial habenula, mediodorsal thalamic nucleus and pons could be observed following substantia innominata or diagonal band injection.

Source of cholinergic input to ferret visual cortex

The source of cholinergic input to ferret visual cortex was investigated with a combination of retrograde transport of horseradish peroxidase and choline acetyltransferase immunohistochemistry. Cholinergic projections to ferret visual cortex arise from basal forebrain cells in the septum, diagonal and nucleus basalis magnocellularis; the largest contribution comes from cells in the caudal part of the nucleus basalis magnocellularis. There is no discernible source in the brainstem.

Developmental changes of nerve growth factor and its mRNA in the rat hippocampus: comparison with choline acetyltransferase

Previous experiments have demonstrated that in the septo-hippocampal system choline acetyltransferase (ChAT) is induced by nerve growth factor (NGF) (Gnahn et al. (1983) Dev. Brain Res. 9, 45-52) and that hippocampal NGF and mRNANGF levels are correlated with the density of cholinergic innervation (Korsching et al. (1985) EMBO J. 4, 1389-1393). In the present investigation we have compared the developmental changes of ChAT, NGF, and mRNANGF levels in this system. During the postnatal development of the hippocampus the time courses of NGF and ChAT were well correlated including the most rapid increase between P12 and P14. This increase in hippocampal NGF was preceded by a corresponding increase in mRNANGF. The developmental changes in hippocampal NGF levels were also closely reflected by corresponding changes in the septum. This, together with previous observations (Korsching et al., 1985) that the adult septum, in spite of relatively high NGF levels, does not contain measurable quantities of mRNANGF, suggests that the NGF levels in the septum are determined by the quantity of NGF transported retrogradely from the field of innervation rather than by local synthesis. During the prenatal period hippocampal NGF levels were relatively high, whereas the mRNANGF was below the level of detection. Since the ingrowth of septal fibers, and with that also the removal of NGF by retrograde transport, begins around birth, the relatively high prenatal NGF levels probably result from an accumulation produced by a small copy number of mRNANGF prior to the removal of NGF by retrograde axonal transport. It is concluded that the correlation of the developmental changes in NGF and mRNANGF with the ChAT activity in the hippocampus further supports the concept of a physiological role of NGF in the central nervous system.

A search for choline acetyltransferase-like immunoreactivity in neurons of cat striate cortex

The goal of this study was to determine whether cat striate cortex contains neurons with choline acetyltransferase-like immunoreactivity. Two different monoclonal antibodies were applied with various fixation protocols. As controls served selected regions of the cat brain and the rat neocortex where cholinergic neurons had been demonstrated previously with independent methods. All experimental protocols labelled the presumptive cholinergic neurons in the central regions but revealed only a few weakly stained neurons in cat striate cortex. These had a non-pyramidal morphology and were scattered throughout all layers.

Distribution of cholinergic neurons and fibers in the hypothalamus of the rat using choline acetyltransferase as a marker

The distribution of choline-acetyltransferase-like immunoreactive structures in the rat hypothalamus and preoptic area was examined by using avidin-biotin immunocytochemistry. We found that the hypothalamus is richly innervated by the cholinergic neuron system. Sites containing cholinergic neurons of varying density were: medial and lateral preoptic areas, septohypothalamic nucleus, median preoptic area, lateral hypothalamus including the perifornical area, anterior hypothalamic nucleus, arcuate nucleus, dorsomedial hypothalamic nucleus, posterior hypothalamic nucleus, dorsal and ventral premammillary nuclei, neuropil mediodorsal to the anterior hypothalamic nucleus, neuropil ventral to the anterior hypothalamic nucleus and ventromedial hypothalamic nucleus, neuropil between lateral hypothalamus and ventromedial hypothalamus, and neuropil between dorsal premammillary nucleus and posterior hypothalamic nucleus. There were also many varicose and non-varicose fibers in the preoptic area and hypothalamus. Two kinds of varicose fibers, one with strong immunoreactivity and the other with weak immunoreactivity, were seen. Non-varicose fibers were also detected in the optic chiasma and habenulo-interpeduncular tract. These fibers were passing fibers.

The immunohistochemical localization of choline acetyltransferase in the cat brain

The distribution of neurons displaying choline acetyltransferase (ChAT) immunoreactivity was examined in the feline brain using a monoclonal antibody. Groups of ChAT-immunoreactive neurons were detected that have not been identified previously in the cat or in any other species. These included small, weakly stained cells found in the lateral hypothalamus, distinct from the magnocellular rostral column cholinergic neurons. Other small, lightly stained cells were also detected in the parabrachial nuclei, distinct from the caudal cholinergic column. Many small ChAT-positive cells were also found in the superficial layers of the superior colliculus. Other ChAT-immunoreactive neurons previously detected in rodent and primate, but not in cat, were observed in the present study. These included a dense cluster of cells in the medial habenula, together with outlying cells in the lateral habenula. Essentially all of the cells in the parabigeminal nucleus were found to be ChAT-positive. Additional ChAT-positive neurons were detected in the periolivary portion of the superior olivary complex, and scattered in the medullary reticular formation. In addition to these new observations, many of the cholinergic cell groups that have been previously identified in the cat as well as in rodent and primate brain such as motoneurons, striatal interneurons, the magnocellular rostral cholinergic column in the basal forebrain and the caudal cholinergic column in the midbrain and pontine tegmentum were confirmed. Together, these observations suggest that the feline central cholinergic system may be much more extensive than previous studies have indicated.

Cholinergic innervation of ferret visual system

The distribution of acetylcholinesterase and choline acetyltransferase in primary visual areas of adult pigmented ferret was determined with cholinesterase histochemistry and choline acetyltransferase immunohistochemistry. In all visual areas the distribution of acetylcholinesterase in the neuropil closely matches that of choline acetyltransferase. In the cerebral cortex acetylcholinesterase and choline acetyltransferase are associated with axons found in every cortical layer and in the white matter. Area 17, identified by Nissl architectonics and cytochrome oxidase histochemistry, is distinguished by having a relatively low density of choline acetyltransferase- and acetylcholinesterase-stained axons in layer IV. Certain cortical non-pyramidal cell types show moderate staining for acetylcholinesterase after relatively long incubations, but no choline acetyltransferase-positive cells are observed in the cortex. In the lateral geniculate nucleus and superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are considerably higher than in cerebral cortex, and choline acetyltransferase-stained axons there display prominent varicosities. The distribution of choline acetyltransferase and acetylcholinesterase in the neuropil of lateral geniculate nucleus and superior colliculus of ferret shows marked laminar variation. For instance, in the lateral geniculate nucleus, the levels of acetylcholinesterase and choline acetyltransferase in the "On" sublaminae of laminae A and A1 are higher than the "Off" sublaminae. In the superficial layers of the superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are highest in the stratum zonale and lowest in the stratum opticum; in the intermediate gray layer of the superior colliculus acetylcholinesterase- and choline acetyltransferase-stained fibres are distributed into dense patches. As in cortex, choline acetyltransferase-positive cell bodies are not found in the lateral geniculate nucleus or superior colliculus, and acetylcholinesterase-stained cell bodies are visible only after long incubations. Cell bodies staining positively for choline acetyltransferase are found in a satellite of the superior colliculus, the parabigeminal nucleus.

Behavioural, biochemical and histochemical effects of different neurotoxic amino acids injected into nucleus basalis magnocellularis of rats

Lesions of the nucleus basalis magnocellularis in rats have been used to investigate functions of the extrinsic cortical cholinergic system which originates from these neurons. These lesions also produce extensive non-specific subcortical damage and associated regulatory and neurological impairments, causing doubt about the specificity of consequent functional impairments. Here, nucleus basalis magnocellularis lesions made with four different neurotoxic amino acids (kainic acid, ibotenic acid, N-methyl-D-aspartate, and quisqualic acid) have been compared. Quisqualic acid produced less subcortical damage and lesser neurological and regulatory impairments than the other toxins at doses that produced comparable cholinergic deafferentation of the neocortex, as assessed both histologically and biochemically. This suggests that these impairments are non-specific rather than specific consequences of cholinergic cell loss. The effects on learning a spatial navigation task were more ambiguous, suggesting the involvement of both cholinergic and non-cholinergic systems. Impairment of a passive shock avoidance task was as great following quisqualic acid as the other neurotoxins, which may suggest a more direct relationship specifically with the decline in cortical cholinergic activity. It is concluded that in the absence of availability of a specific cholinergic neurotoxin, quisqualic acid produces less non-specific neuroanatomical and neurological side effects than the more widely used toxins N-methyl-D-aspartate, kainic acid or ibotenic acid.

Quantitative light microscopic autoradiographic localization of cholinergic muscarinic receptors in the human brain: forebrain

The distribution of muscarinic cholinergic receptors in the human forebrain and cerebellum was studied in detail by quantitative autoradiography using N-[3H]methylscopolamine as a ligand. Only postmortem tissue from patients free of neurological diseases was used in this study. The highest densities of muscarinic cholinergic receptors were found in the striatum, olfactory tubercle and tuberal nuclei of the hypothalamus. Intermediate to high densities were observed in the amygdala, hippocampal formation and cerebral cortex. In the thalamus muscarinic cholinergic receptors were heterogeneously distributed, with densities ranging from very low to intermediate or high. N-[3H]Methylscopolamine binding was low in the hypothalamus, globus pallidus and basal forebrain nuclei, and very low in the cerebellum and white matter tracts. The localization of the putative muscarinic cholinergic receptors subtypes M1 and M2 was analysed in parallel using carbachol and pirenzepine at a single concentration to partially inhibit N-[3H]methylscopolamine binding. Mixed populations of both subtypes were found in all regions. M1 sites were largely predominant in the basal ganglia, amygdala and hippocampus, and constituted the majority of muscarinic cholinergic receptors in the cerebral cortex. M2 sites were preferentially localized in the diencephalon, basal forebrain and cerebellum. In some areas such as the striatum and substantia innominata there was a tendency to lower densities of muscarinic cholinergic receptors with increasing age. In general, we observed a slight decrease in M2 sites in elderly cases. Muscarinic cholinergic receptor concentrations seemed to be reduced following longer postmortem periods. The distribution of acetylcholinesterase was also studied using histochemical methods, and compared with the localization of muscarinic cholinergic receptors and other cholinergic markers. The correlation between the presence of muscarinic cholinergic receptors and the involvement of cholinergic mechanisms in the function of specific brain areas is discussed. Their implication in neurological diseases is also reviewed.

Colocalization of gamma-aminobutyric acid and acetylcholinesterase in rodent cortical neurons

We have previously demonstrated that neurons of the rat cerebral cortex which stain positively for acetylcholinesterase are not likely to be cholinergic since they do not colocalize with choline acetyltransferase immunoreactivity [Levey, Rye, Wainer, Mufson and Mesulam (1984) Neuroscience 9, 9-22]. These noncholinergic acetylcholinesterase-positive cells were similar in morphology to cortical neurons which localize gamma-aminobutyric acid or glutamate decarboxylase immunoreactivity. In order to investigate the possibility that the two substances may be colocalized to the same cortical neurons, gamma-aminobutyric acid immunohistochemistry and acetylcholinesterase histochemistry were combined in single sections of rat cerebral cortex. We found that 18% of gamma-aminobutyric acid-immunoreactive cortical neurons are also acetylcholinesterase-positive, and about 36% of acetylcholinesterase-positive cells are gamma-aminobutyric acid-immunoreactive. Neurons which colocalized both substances were multipolar and bipolar neurons in cortical laminae II-VI and were observed in every cortical area examined. The possibility that gamma-aminobutyric acid-immunoreactive/acetylcholinesterase-positive cortical neurons may be postsynaptic targets of cholinergic afferents to the cerebral cortex is discussed.

Cholinergic neurons in the hippocampus. A combined light- and electron-microscopic immunocytochemical study in the rat

We report here on cholinergic neurons in the rat hippocampal formation that were identified by immunocytochemistry employing a monoclonal antibody against choline acetyltransferase (ChAT), the acetylcholine-synthesizing enzyme. In general, ChAT-immunoreactive cells were rare, but were observed in all layers of the hippocampus proper and fascia dentata with a preponderance in zones adjacent to the hippocampal fissure and in the part of CA1 bordering the subiculum. All immunoreactive cells found were non-pyramidal neurons. They were relatively small with round or ovoid perikarya, which gave rise to thin spine-free dendrites. These hippocampal neurons were very similar to ChAT-immunoreactive cells in the neocortex of the same animals but were quite different from cholinergic neurons in the basal forebrain, medial septal nucleus, and neostriatum, which were larger and more intensely immunostained. Electron-microscopic analysis of ChAT-immunoreactive cells in the hippocampus and fascia dentata revealed synaptic contacts, mainly of the asymmetric type, on cell bodies and smooth proximal dendrites. The nuclei of the immunoreactive cells exhibited deep indentations, which are characteristic for non-pyramidal neurons. Our results provide evidence for an intrinsic source of the hippocampal cholinergic innervation in addition to the well-established septo-hippocampal cholinergic projection.

Choline acetyltransferase immunohistochemical staining in the goldfish (Carassius auratus) brain: evidence that the Mauthner cell does not contain choline acetyltransferase

In the hatchetfish, the Mauthner cell (M-cell) is thought to be cholinergic based on electrophysiological studies using cholinergic agents and on the localization of acetylcholinesterase (AChE) and alpha-bungarotoxin to M-cell-giant fiber synapses. Immunocytochemical studies have shown that mammalian and non-mammalian cholinergic neurons stain positive for choline acetyltransferase (ChAT), the enzyme responsible for synthesizing acetylcholine. We processed tissue from the goldfish (Carassius auratus) for the immunohistochemical detection of ChAT using the monoclonal antibody AB8 and the peroxidase-antiperoxidase procedure. ChAT immunoreactivity was found in selected areas of the goldfish brain including the cranial nerve nuclei and the ventral horn motoneurons of the spinal cord. Interestingly, the M-cell soma which stains positive for AChE was ChAT negative. This immunohistochemical evidence does not support cholinergic functioning of the Mauthner cell.

[3H]ketanserin (serotonin type 2) binding increases in rat cortex following basal forebrain lesions with ibotenic acid

The response of the serotonergic system following injury to the basal forebrain cholinergic system was investigated in rats. The density of 5-hydroxytryptamine (serotonin) type 2 (S2) receptor sites in the frontal cortex and hippocampus was determined 1 week and 4 months after production of lesions by injections of ibotenic acid into the medial septum and nucleus basalis magnocellularis. One week later, the number of S2 receptor sites in the frontal neocortex, as defined by [3H]ketanserin binding, was unchanged. Four months later, the number of [3H]ketanserin binding sites (and Bmax) was increased and high-affinity [3H]serotonin uptake was decreased in the frontal neocortex, but not in the hippocampus, relative to unlesioned controls. Choline acetyltransferase (acetyl-CoA:choline O-acetyltransferase; EC 2.3.1.6) activity was decreased significantly in the frontal neocortex and hippocampus 1 week and 4 months after surgery. The change in frontal neocortical S2 receptor site density was inversely related to the level of choline acetyltransferase activity, was specific for cholinergic denervation associated with the cortex but not the hippocampus, and may represent a localized denervation supersensitivity due to degeneration of median raphe cortical afferents.

Cholinergic innervation of the cat striate cortex: a choline acetyltransferase immunocytochemical analysis

In area 17 of adult cats the morphology, distribution, and synaptology of cholinergic elements were examined by immunocytochemical methods with a monoclonal antibody against choline acetyltransferase (ChAT). ChAT(+) fibers are present throughout the entire depth of the cortex but are particularly dense in layer I. Typically these fibers are very thin and possess numerous irregularly spaced varicosities. Except in layer I and deep layer VI, where the fibers tend to run parallel to the pial surface, they appear to be randomly oriented. At the electron microscope level, immunolabeling was present in unmyelinated fibers of irregular contour and diameter. Most of the ChAT(+) varicose profiles contained mitochondria and round vesicles. Synaptic complexes were relatively infrequent and tended to be of the symmetrical type. They were located mostly on dendritic shafts and only rarely on cell bodies and dendritic spines. Both pyramidal and nonpyramidal cells were found to be innervated by cholinergic afferents. These anatomical data are consistent with the known physiology of acetylcholine in the visual cortex, which indicates that it acts as a modulator of cortical excitability.

Ultrastructural organization of choline-acetyltransferase-immunoreactive fibres innervating the neocortex from embryonic ventral forebrain grafts

Suspension grafts of foetal tissue rich in cholinergic neurones were transplanted into the frontoparietal cortex of rats that had previously undergone deafferentation of the extrinsic cholinergic innervation of the cortex by injection of ibotenic acid into the nucleus basalis magnocellularis. The cortical tissue containing the graft was processed for electron microscopic immunocytochemistry by using a monoclonal antibody to choline acetyltransferase (ChAT) in order to examine the contacts established between cholinergic fibres from the graft and the host neocortex. The density, distribution, and targets of this graft-host innervation were compared with those seen in the intact and deafferented cortex. ChAT-positive fibres in both grafted and control animals formed extensive synaptic connections with various cortical neural elements--those of graft origin being of similar morphology to those in the intact cortex. However, the distribution of postsynaptic cortical targets of the graft-derived ChAT-immunoreactive boutons was abnormal, such that a greater percentage of such terminals formed synaptic contacts with neuronal perikarya, especially layer V pyramidal neurones, than was seen in control brains. It is possible that the formation of new synaptic contacts between the embryonic graft and host frontoparietal cortex may, in part, be necessary for the restoration of functional activity that has been previously reported in these grafted animals.

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.

Cholinergic neurons and fibres in the rat visual cortex

Choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme, was localized immunocytochemically in neurons and fibres in the rat visual cortex using a monoclonal antibody. ChAT-labelled cells were non-pyramidal neurons, primarily of the bipolar form, distributed in layers II through VI but concentrated in layers II & III. Their perikarya contained a large nucleus and a small amount of perinuclear cytoplasm. The somata and dendrites of all labelled cells received Gray's type I and type II synapses. ChAT-stained axons formed a dense and diffuse network throughout the visual cortex and particularly in layer V. Electron microscopy revealed that the great majority formed type II synaptic contacts with dendrites of various sizes, unlabelled non-pyramidal somata and, on a few occasions, with ChAT-labelled cells. However, a very small number of terminals appeared to form type I synaptic contacts. This study describes the morphological organization of the cholinergic system in the visual cortex, the function of which has been under extensive investigation.

Basal forebrain neurons provide major cholinergic innervation of primate neocortex

In 3 monkeys, lesions were made in the basal forebrain by microinjections of ibotenic acid into the nucleus basalis. Bilateral samples of multiple neocortical gyri were assayed for the activity of choline acetyltransferase. Compared to control hemispheres, enzyme activity was reduced up to 69% in the neocortex ipsilateral to the lesion; in addition, acetylcholinesterase staining was decreased at the lesioned site and in the ipsilateral cortex. These results support the concept that the principal cholinergic innervation of the primate neocortex is derived from axons and nerve terminals of neurons whose perikarya are located in the basal forebrain, particularly the nucleus basalis.

Monoclonal antibodies to human hypoglossal nucleus which stain neurons and astrocytes in normal brains and brains from cases of Alzheimer-type dementia

Monoclonal antibodies were raised to membranes of hypoglossal nuclei from normal human post-mortem brain. Two of these clones were recloned to yield antibodies ES.18 and ES.19. Antibody ES.18 stained some, but not all, neuronal perikarya in the medulla oblongata and other brain areas. Neurons stained by this antibody did not have a common neurotransmitter or physiological function, although they tended to be large. Perikarya in the basal forebrain nucleus from a case of Alzheimer-type dementia were stained much more intensely by ES.18 than were these perikarya in a control brain. Antibody ES.19 did not stain neuronal perikarya but stained glial fibrillary acidic protein-positive processes below the pia, in the subependymal layer and in the molecular layer of the cerebellum of control and Alzheimer brains. This antibody also stained the numerous glial fibrillary acidic protein-positive astrocytes in Alzheimer cerebral cortex, but did not stain glial fibrillary acidic protein-positive astrocytes in the white matter of brains from controls or cases of Alzheimer-type dementia. The staining pattern of ES.19 suggests that fibrous astrocytes in Alzheimer cerebral cortex are antigenically different from fibrous astrocytes in white matter.

Prenatal development of nucleus basalis complex and related fiber systems in man: a histochemical study

To provide parameters for study of the "cholinergic" innervation of a human fetal cerebrum, we have analyzed the prenatal development of histochemical reactivity in the nucleus basalis complex (a magnocellular complex known to contain a high concentration of cholinergic perikarya). Brains from fetuses and premature infants ranging between 8 and 35 weeks of gestation were frozen cut and processed by the thiocholine method for the demonstration of acetylcholinesterase activity. Since no consistent results were obtained with inhibitors on the material younger than 15 weeks, the histochemical reactivity for early stages was expressed as the total cholinesterase reactivity. The first sign of histochemical differentiation of the basal telencephalon is the appearance of a dark cholinesterase reactive "spot" situated between the developing lenticular nucleus and basal telencephalon surface as early as 9 weeks of gestation. The first cholinesterase reactive bundle connects this reactive area (nucleus basalis complex anlage) with the strongly reactive fiber system situated along the dorsal side of the optic tract. During the next "stage" (10.5 weeks), there is a significant increase in the size of the nucleus basalis complex and strongly cholinesterase reactive neuropil occupies the sublenticular, diagonal and septal areas. At this stage we have seen two new cholinesterase-reactive bundles: one well developed cholinesterase reactive fiber stratum approaching (but not penetrating) the neocortical anlage through the external capsule and another minute bundle running towards the medial limbic cortex through the precommissural septum. The supraoptic fiber system can be traced now to the pregeniculate area and the tegmentum. At 15 weeks, the first acetylcholinesterase reactive perikarya appear and the nucleus basalis complex anlage becomes segregated into several strongly reactive territories, corresponding in position to the medial septal, diagonal and basal nuclei as defined on adjacent Nissl stained sections. At this stage, fibers from the nucleus basalis complex enter the "white" matter of frontal, temporal, parietal and occipital parts of the cerebral hemisphere via the external capsule. Between 15 and 18 weeks, acetylcholinesterase fibers spread throughout the "white" matter of the cerebral hemisphere. In the next "stage" (18-22 weeks), strongly reactive fibers can be followed from the nucleus basalis below the putamen and through the external capsule to the transient, synapse-rich subplate zone of frontal, temporal, parietal and occipital cortices.(ABSTRACT TRUNCATED AT 400 WORDS)

A correlated light and electron microscopic immunocytochemical study of cholinergic terminals and neurons in the rat amygdaloid body with special emphasis on the basolateral amygdaloid nucleus

The cholinergic innervation of the rat basolateral amygdaloid nucleus (BL) was determined by the immunocytochemical localization of the acetylcholine biosynthetic enzyme, choline acetyltransferase (ChAT). ChAT-immunoreactive (ChAT-IR) elements were observed throughout the BL in the form of fine puncta and varicose fibers. Electron microscopy revealed that the immunoreactive puncta represented small terminals (0.3-1.2 micron), most of which formed synaptic contacts with unlabeled dendritic shafts or spines. Less frequently, ChAT-IR terminals established synaptic contacts with large neuronal cell bodies, which had all the characteristics of projection neurons as defined on the basis of axonal projections to the ventral striatum. ChAT-IR terminals were sometimes seen to form synaptic contacts with small neuronal cell bodies, including those of ChAT-IR neurons. The ChAT-IR boutons contained pleomorphic clear vesicles of varying size, and the large majority of the synapses were of the symmetric type. Small ChAT-IR neurons were observed in all parts of the BL. Although the ChAT-IR cell bodies varied widely in shape from typical fusiform to round, most had a more or less oval shape with a major diameter of 10-14 micron. Most of the ChAT-IR neurons seemed to display a radial bipolar dendritic pattern, but multipolar cells were also observed. The ChAT-IR neurons contained an indented nucleus, which was often eccentrically located and surrounded by a thin or moderately thin rim of cytoplasm. The results obtained are discussed in relation to a quasi-cortical organization of the BL.

The localization of central cholinergic neurons

Over the past decade our understanding of the localization of central cholinergic neurons has greatly increased. Interest in these systems has also intensified due to the involvement of cholinergic mechanisms in Alzheimer's disease. The distribution of central cholinergic neurons is reviewed, focusing on recent work in experimental animals. The pharmacohistochemical procedure for acetylcholinesterase and the development of antibodies to choline acetyltransferase are two of the major technical advances that have shaped our knowledge of the distribution of central cholinergic neurons. The results, advantages and limitations of both techniques are discussed. A discussion of the phenomenon of coexistence of acetylcholine with neuroactive peptides in central neurons is also included.

Morphology of acetylcholinesterase-containing neurons in primary cultures of dissociated rat cerebral cortex

Acetylcholinesterase-containing neurons were investigated in primary cultures of cerebral cortex. Neuronal cholinesterase staining was essentially totally attributable to acetylcholinesterase based on its pattern of sensitivity to pharmacological inhibitors. The mean percentage of stained neurons in the cultures was 2.17. Stained neurons of all morphologies were detected: however, the majority of the cells possessed bipolar morphology. The stained bipolar neurons were not a homogeneous morphological population.

Functional and neurochemical cortical cholinergic impairment following neurotoxic lesions of the nucleus basalis magnocellularis in the rat

The effect of kainic and quinolinic acid on cortical cholinergic function was examined following injections of these agents into the nucleus basalis magnocellularis (nbm) or into the frontoparietal cortex. The release of cortical 3H-acetylcholine (3H-ACh), high affinity choline uptake (HACU) and acetylcholinesterase was measured 7 days following injections of saline (control), kainic acid (4.7 nmoles) and quinolinic acid (60, 150 and 300 nmoles) into the nbm. These cortical cholinergic parameters were also examined after injections of saline (control), kainic acid (9.4 nmoles) and quinolinic acid (300 nmoles) into the fronto-parietal cortex. The release of 3H-ACh, HACU and AChE was significantly reduced in animals injected with kainic or quinolinic acid into the nbm. Histological examination of stained sections showed a loss of cell bodies in the region of the nbm and the globus pallidus. The size of the lesion produced by quinolinic acid was proportional to the dose injected into the nbm. In animals injected with kainic acid or quinolinic acid into the cerebral cortex, the release of 3H-ACh, HACU and AChE was not significantly reduced when compared with control animals, although histological examination of stained cortical sections showed a marked loss of cortical neurons. The results show that quinolinic acid, an endogenous neuroexcitant, produces a deficit of cholinergic function similar to that described in the cortical tissue of patients with senile dementia of Alzheimer's type. The toxic effects of quinolinic acid on cortical cholinergic function are due to its action on cholinergic cell bodies in the nbm.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase and somatostatin-immunoreactivity coexist in human neocortex

Immunohistochemistry was combined with enzyme histochemistry to examine the localization of somatostatin (SOM) and acetylcholinesterase (AChE) in the human neocortex. Many of the SOM-immunoreactive cortical neurons were found to display specific AChE activity. Similar coexistence was seen in the rat cortex. In contrast, AChE and SOM appear to be present in distinct cell groups in the human caudate nucleus.