Serotonin-immunoreactive neurons in the median protocerebrum and suboesophageal ganglion of the sphinx moth Manduca sexta.

Serotonin-immunoreactive neurons in the median protocerebrum and suboesophageal ganglion of the sphinx moth Manduca sexta were individually reconstructed. Serotonin immunoreactivity was detected in 19-20 bilaterally symmetrical pairs of interneurons in the midbrain and 10 pairs in the suboesophageal ganglion. These neurons were also immunoreactive with antisera against DOPA decarboxylase. All major neuropil regions except the protocerebral bridge are innervated by these neurons. In addition, efferent cells are serotonin-immunoreactive in the frontal ganglion (5 neurons) and the suboesophageal ganglion (2 pairs of neurons). The latter cells probably give rise to an extensive network of immunoreactive terminals on the surface of the suboesophageal ganglion and suboesophageal nerves. Most of the serotonin-immunoreactive neurons show a gradient in the intensity of immunoreactive staining, suggesting low levels of serotonin in cell bodies and dendritic arbors and highest concentrations in axonal terminals. Serotonin-immunoreactive cells often occur in pairs with similar morphological features. With one exception, all serotonin-immunoreactive neurons have bilateral projections with at least some arborizations in identical neuropil areas in both hemispheres. The morphology of several neurons suggests that they are part of neuronal feedback circuits. The similarity in the arborization patterns of serotonin-immunoreactive neurons raises the possibility that their outgrowing neurites experienced similar forces during embryonic development. The morphological similarities further suggest that serotonin-immunoreactive interneurons in the midbrain and suboesophageal ganglion share physiological characteristics.

[Localization of efferent sympathetic neurons and afferent neurons in dorsal root ganglia innervating the heart]. / Localizatsiia éfferentnykh simpaticheskikh neironov i afferentnykh neironov v spinal'nykh gangliiakh. innerviruiushchikh serdtse.

The retrograde transport of horseradish peroxidase (HRP) has been used to study the localization and the number of neurons innervating the heart in the right stellate ganglion and accessory cervical ganglion, spinal cord and dorsal root ganglia of the cat. HRP was applied to the central cuts of anastomose of the stellate ganglion with the vagal nerve, of the vagosympathetic trunk caudal to anastomose and of the inferior cardiac nerve. HRP-labelled neurons were detected in the stellate ganglion in the regions which give off nerves, whereas in the accessory cervical ganglion labelled neurons were distributed throughout the whole ganglion. HRP-stained cells were found in the anastomose. In the spinal cord labelled neurons were detected in the lateral horn of T1-T5 segments. In the dorsal root ganglion the greatest number of neurons was observed in T2-T4 segments.

The efferent innervation of the genital chamber by an identified serotonergic neuron in the female cricket Acheta domestica.

The serotonergic innervation of the genital chamber of the female cricket, Acheta domestica, has been investigated applying anti-serotonin (5-HT) immunocytochemistry at both light- and electron-microscopic levels as well as using conventional electron microscopy. Whole mount and pre-embedding chopper techniques of immunocytochemistry reveal a dense 5-HT-immunoreactive network of varicose fibers in the musculature of the genital chamber. All of these immunoreactive fibers originate from the efferent serotonergic neuron projecting through the nerve 8v to the genital chamber (Hustert and Topel 1986; Elekes et al. 1987). At the electron-microscopic level, 5-HT-immunoreactive nerve terminals, which contain small (50-60 nm) and large (approximately 100 nm) agranular vesicles as well as granular vesicles (approximately 100 nm), contact the muscle fibers or the sarcoplasmic processes without establishing specialized neuromuscular connections. In addition to the 5-HT-immunoreactive axons, two types of immunonegative axons can also be found in the musculature. By use of conventional electron microscopy, three ultrastructurally distinct types of axon processes can be observed, one of which resembles 5-HT-immunoreactive axons. While the majority of the varicosities do not synapse on the muscle fibers, terminals containing small (50-60 nm) agranular vesicles occasionally form specialized neuromuscular contacts. It is suggested that the 5-HTergic innervation plays a non-synaptic modulatory role in the regulation circular musculature in the genital chamber of the cricket, while the musculature as a whole may be influenced by both synaptic and modulatory mechanisms.

Locus coeruleus neurons in the rat containing neuropeptide Y, tyrosine hydroxylase or galanin and their efferent projections to the spinal cord, cerebral cortex and hypothalamus.

The efferent projections of locus coeruleus neurons which contain neuropeptide Y-, tyrosine hydroxylase- or galanin-like immunoreactivity were investigated using the indirect immunofluorescence technique combined with the retrograde transport of the fluorescent substance Fast Blue. Four groups of rats received injections of Fast Blue: (1) bilaterally into the mid-thoracic spinal cord (T6-T7); (2) unilaterally into the low cervical spinal cord (C4-C5); (3) unilaterally into the paraventricular, periventricular and dorsomedial hypothalamic nuclei; and (4) unilaterally into five sites in the cerebral cortex (frontal, cingulate and striate cortex). Efferent projections to the spinal cord, hypothalamus and cerebral cortex from neuropeptide Y-, tyrosine hydroxylase- and galanin-containing locus coeruleus cells were observed. A higher percentage of the peptidergic locus coeruleus neurons projected to the hypothalamus than to the spinal cord or cerebral cortex. The distribution and morphology of the neuropeptide Y- and galanin-containing neurons in the locus coeruleus were also investigated. Neuropeptide Y-like immunoreactivity and galanin-like immunoreactivity were found in small, medium and large multipolar neurons, as well as in fusiform locus coeruleus cells. The neuropeptide Y- and galanin-immunoreactive neurons were found throughout the locus coeruleus. In the caudal locus coeruleus, they were primarily located in the dorsal portion. Neuropeptide Y-like immunoreactivity and galanin-like immunoreactivity were only seen in a few tyrosine hydroxylase-positive neurons of the subcoeruleus group. The data show that the peptide-containing locus coeruleus neurons have efferent projections to the spinal cord, hypothalamus and cerebral cortex. The locus coeruleus may be divided into functional subdivisions dependent on the region of the locus coeruleus, the neurotransmitter/neuropeptide(s) contained within the neurons and their efferent projections.

Light- and electron-microscopic study of gamma-aminobutyric-acid-like immunoreactivity in the guinea pig organ of Corti.

With light and electron microscopy, gamma-aminobutyric-acid (GABA)-like immunoreactivity was examined in the guinea pig organ of Corti. In whole-mount preparations, although GABA-like immunoreactivity was present within efferent components in all turns of the cochlea, it was more intense apically. At the ultrastructural level, GABA-like immunoreactivity was clearly restricted to the efferent system, appearing in axons of the inner and tunnel spiral bundles, in axons crossing the tunnel of Corti, and in terminals filled with numerous labeled vesicles synapsing on outer hair cells.

GABA-like immunoreactivity in the squirrel monkey vestibular endorgans.

The localization of gamma-aminobutyric acid (GABA)-like immunoreactivity in the squirrel monkey vestibular endorgans was investigated using an antiserum against GABA coupled with glutaraldehyde to bovine serum albumin. GABA-like immunoreactivity was found in nerve fibers and bouton-type terminals, both in the cristae ampullares and the maculae. The location of positive staining corresponded better with known efferent than afferent components of the vestibular periphery.

Vestibular and cochlear efferent neurons in the monkey identified by immunocytochemical methods.

Attempts were made to identify vestibular (VEN) and cochlear (CEN) efferent neurons in the squirrel monkey using retrograde transport of horseradish peroxidase (HRP) and immunocytochemical methods. HRP implants in the ampulla of the lateral semicircular duct retrogradely labeled cells of VEN bilaterally and some cells of CEN. VEN located lateral to the rostral part of the abducens nucleus formed a compact collection of cells, all of which were immunoreactive only to antisera for choline acetyltransferase (ChAT). CEN, identified by immunoreactivity to ChAT were located at the hilus of the lateral superior olive (LSO), along the lateral border of the LSO and sparsely near lateral parts of the ventral trapezoid nucleus (VTN). A small number of cells and fibers near the border of the VTN and lateral to the LSO were immunoreactive for leucine enkephalin (L-ENK). Fibers immunoreactive for L-ENK also were identified in the hilus of the LSO. No cells of the superior olivary complex were immunoreactive for antisera to ChAT, L-ENK, substance P, gamma-aminobutyric acid or glutamic acid decarboxylase. Cells of VEN and CEN can be identified by their immunoreactivity to ChAT, and some cells and fibers of CEN also contain L-ENK.

Neurotransmitters in the cerebral cortex.

This article surveys the conventional neurotransmitters and modulatory neuropeptides that are found in the cerebral cortex and attempts to place them into the perspective of both intracortical circuitry and cortical disease. The distribution of these substances is related, where possible, to particular types of cortical neuron or to afferent or efferent fibers. Their physiological actions, where known, on cortical neurons are surveyed, and their potential roles in disease states such as the dementias, epilepsy, and stroke are assessed. Conventional transmitters that occur in afferent fibers to the cortex from brain-stem and basal forebrain sites are: serotonin, noradrenaline, dopamine, and acetylcholine. All of these except dopamine are distributed to all cortical areas: dopamine is distributed to frontal and cingulate areas only. The transmitter in thalamic afferent systems is unknown. Gamma aminobutyric acid (GABA) is the transmitter used by the majority of cortical interneurons and has a profound effect upon the shaping of receptive field properties. The vast majority of the known cortical peptides are found in GABAergic neurons, and the possibility exists that they may act as trophic substances for other neurons. Levels of certain neuropeptides decline in cases of dementia of cortical origin. Acetylcholine is the only other known transmitter of cortical neurons. It, too, is contained in neurons that also contain a neuropeptide. The transmitter(s) used by excitatory cortical interneurons and by the efferent pyramidal cells is unknown, but it may be glutamate or aspartate. It is possible that excitotoxins released in anoxic disease of the cortex may produce damage by acting on receptors for these or related transmitter agents.

The facial "motor" nerve of the rat: control of vibrissal movement and examination of motor and sensory components.

Rhythmical whisking of the mystacial vibrissae at about 7 Hz during exploration is one of the most conspicuous behavioral patterns in the rat. To identify the final common pathway for vibrissal movement, individual motor branches of the facial nerve, including the posterior auricular, temporal, zygomatic, buccal, marginal mandibular, cervical, stylohyoid, and posterior digastric branches, were cut, either singly or in various combinations. We found that vibrissal movement could be abolished only by transection involving the buccal branch and the upper division of the marginal mandibular branch. To trace back the central origins of the buccal and marginal mandibular, as well as the other branches of the facial nerve, all distal to the stylomastoid foramen, horseradish peroxidase (HRP) was applied to the cut proximal ends of these individual branches. The retrograde HRP labelling in the facial motor nucleus revealed topographical representation of these branches in which the buccal and marginal mandibular branches were represented laterally. The stylohyoid and posterior digastric branches originated from cells in the suprafacial nucleus. Consistent with earlier observations with intramuscular HRP injections, the motoneuronal population devoted to vibrissal movement did not seem to be substantially larger than that for other facial movements. An additional examination was made of the labelled afferent component of the facial motor nerve. We confirmed and extended previous findings that none of the above facial motor nerve branches, except the posterior auricular branch, contained a significant number of afferent fibers originating from the geniculate ganglion, the sensory ganglion of the seventh nerve. In addition, no labelling was seen in the mesencephalic trigeminal nucleus or trigeminal ganglion. These findings, in combination, suggest that, with the exception of the posterior auricular branch, all the facial motor nerve branches, including those involved in vibrissal movement, are almost entirely efferent.

Amino acid labeling patterns in the efferent innervation of the cochlea: an electron microscopic autoradiographic study.

Light microscopic autoradiography and electron microscopic autoradiography were used to study the distribution of label in the cochlear efferents following in vivo incubation with tritiated amino acids. Two basic patterns of labeling were observed. These patterns correspond closely to the lateral and medial superior olivary complex (SOC) olivocochlear systems identified by Warr and Guinan ('79, Brain Res. 173:152-155). Our electron microscopic observations suggest that, at least in the gerbil, the complete separation of outer hair cell (OHC) versus inner hair cell (IHC) efferent innervation proposed by these investigators based upon light microscopic data does not occur. Rather, our data suggest that while the lateral SOC system supplies endings only to the region under the IHC, the medial SOC system may supply endings beneath both the IHCs and OHCs.

The connections of the hippocampal region. New observations on efferent connections in the guinea pig, and their functional implications.

This article deals with the efferent connections of the hippocampal region, and considers the functional implications of these projections. The hippocampus receives indirect sensory information from many structures in the brain. Most of these afferents terminate in the superficial layers (I-III) of the entorhinal area. From cells in layers II and III of entorhinal area projections arise which terminate in hippocampus and fascia dentata, the perforant paths. Internal hippocampal projections constitute a unidirectional system of connections which project back to the deep layers (IV-VI) of the entorhinal area. The efferents from these layers may be divided into cortically terminating efferents, which originate from layer IV, and subcortically terminating efferents, which originate from layers V and VI. The cortically terminating projections end in regions of association cortex, and in limbic cortex. The subcortical projections terminate in the caudate, the putamen, and the accumbens nucleus. A hippocampal influence on these subcortical structures may seem surprising, but is logical when one takes into consideration reports on the functional associations between the striatum and the hippocampus. The findings suggest that the role of the hippocampus may be to gather input from all sensory modalities, to assign priorities continuously between these inputs, and as a result, to modify behavior via its influence on subcortical motor centres.

Ultrastructural relation between cortical efferents and terminals containing enkephalin-like immunoreactivity in rat neostriatum.

The interrelationships between cortical efferents and terminals containing enkephalin-like immunoreactivity (ELI) were examined by combining anterograde degeneration with electron microscopic immunocytochemistry in the adult rat neostriatum. Two days following unilateral removal of the cerebral cortex, the brains were fixed by aortic arch perfusion, then sectioned and processed for the immunocytochemical localization of an antiserum directed against methionine (Met5)-enkephalin. The observed relationships between the degenerating cortical efferents and immunocytochemically labeled terminals were of two types. In the first, the degenerating and ELI containing terminals converged on the same unlabeled dendrite or dendritic spine. In the second, terminal and preterminal axons of the ELI containing neurons had one surface directly apposed to the plasma membrane of a degenerating axon terminal. These findings support the concept that neurons containing opioid peptides and cortical efferents modulate the output of common recipient neurons and may also directly interact with each other through presynaptic axonal mechanisms in the rat neostriatum.

Norepinephrine depletion in idiopathic orthostatic hypotension.

Five patients with idiopathic orthostatic hypotension and defective vasoconstrictor responses to the Valsalva maneuver and to application of ice to the forehead were found to have absent vasoconstriction in the forearm in response to intra-arterial administration of tyramine and enhanced vasoconstrictor responses in response to intra-arterial administration of norepinephrine. These findings strongly suggested norepinephrine depletion from the nerve endings and inability of the sympathetic nerve endings to take up norepinephrine. The depletion of norepinephrine from sympathetic nerve endings was confirmed in four patients by demonstrating histochemically the absence of catecholamine-specific fluorescence in sympathetic vasomotor nerves from deltoid muscle. It is suggested that depletion of norepinephrine from nerve endings was responsible for autonomic dysfunction and orthostatic hypotension in these patients.

Sex difference in the number of the sympathetic neurons in the spinal cord of the cat.

Counts of preganglionic sympathetic neurons in the spinal cords of four male and four female cats were obtained. The number of these neurons in males was significantly greater than that in females. These data suggest that the numbers of neurons in the mammalian central nervous system are different in the two sexes.