Neuropeptide Y-like immunoreactivity in the brain stem respiratory nuclei of the cat

The dorsal vagal complex of the ferret: anatomical and immunohistochemical studies

To further the understanding of gastrointestinal function in this species, and in particular to advance our own work concerning central emetic pathways, the cytoarchitecture and the distribution of eight neurochemicals were studied in the ferret dorsal vagal complex (DVC; area postrema, nucleus of the solitary tract [nTS] and dorsal motor nucleus of the vagus). The cytoarchitectural features of this region in the ferret were similar to those seen in other species; however, the ferret possesses a particularly large and distinct subnucleus gelatinosus of the nTS. Dense calcitonin gene-related peptide-immunoreactivity was found in the gelatinous, interstitial and commissural subnuclei of the nTS, with lesser amounts in other regions of the DVC. Enkephalin-immunoreactivity of varying densities was found throughout the DVC. Moderate to dense galanin-immunoreactivity was observed throughout the DVC, with the exception of the subnucleus gelatinosus of the nTS, from which it was virtually absent. Dense neuropeptide Y-immunoreactivity was observed in the subnucleus gelatinosus and interstitial subnucleus, with moderate staining in other regions of the DVC. Neurotensin immunoreactivity was very sparse or absent. Immunoreactivity for serotonin was sparsely distributed throughout the DVC. Moderate somatostatin-immunoreactivity was observed over a large portion of the DVC, but was virtually absent from the gelatinosus and interstitial subnuclei. Substance P immunoreactivity was observed throughout the DVC and was particularly dense in the dorsal/dorsolateral subnucleus and the dorsal aspects of the medial and commissural subnuclei. In terms of its cytoarchitecture the DVC of the ferret is more similar to the cat than the rat, especially with regard to the area postrema and the subnucleus gelatinosus of the nTS. The distribution of neuroactive substances was largely similar to other species; however, differences were present particularly in patterns of immunoreactivity for enkephalin, serotonin, neuropeptide Y and somatostatin.

Neuropeptide Y-like substances are released from the rostral brainstem of cats during the muscle pressor response

1. In this study, the release of immunoreactive neuropeptide Y (NPY)-like substances (irNPYs) was measured from the rostral brainstem in response to fatiguing isometric contractions of the hindlimb muscle of cats anaesthetized with alpha-chloralose. 2. The irNPYs were measured using a solid phase autoradiographic immunoassay. NPY antibody-coated glass microelectrodes were inserted stereotaxically into the rostral brainstem during rest and contractions. Control procedures such as passive leg flexing, stimulation of the central end of the cut tibial nerve, brief repeated carotid occlusions and carotid sinus nerve stimulations were performed to determine whether patterns of release of irNPYs were specific to the pathways activated during the muscle pressor response. 3. During isometric contractions, the mean arterial blood pressure (MABP) and heart rate (HR) increased by 60-70 mmHg and 15-20 beats min-1, respectively. Only the brief carotid occlusions caused a similar increase in MABP and HR. 4. During isometric contractions, less irNPYs were released from sites in the lateral reticular nucleus, lateral tegmental field and vestibular nuclei at a level in the brainstem 4.0-4.4 mm rostral to the obex. In contrast, irNPYs were released from sites near the lateral tegmental field and nucleus ambiguus at a more caudal level tested (1.3 mm anterior to the obex) in response to contractions. Brief carotid occlusions caused a release of irNPYs from the lateral reticular nucleus on the contralateral side of the brainstem (at 3.5 mm anterior to the obex). None of the other procedures resulted in a release of irNPYs from these sites in the brainstem. 5. These data indicate there are differences in the patterns of release of irNPYs in response to activation of reflex pathways which increase arterial pressure. Given the sites in the rostral brainstem where irNPYs were released, irNPYs may be involved with the central regulation of arterial pressure during the muscle pressor response.

Release of immunoreactive neuropeptide Y from brainstem sites in the cat during isometric contractions

Fatiguing isometric contractions of the left hind-limb muscles in cats anesthetized with alpha-chloralose caused mean arterial pressure to increase by 82 +/- 18 mmHg above resting and post-contraction levels and heart rates to increase by 15 +/- 5 beats/min. Contractions were performed by stimulating the tibial nerve via a microprocessor-controlled stimulator. Glass microprobes, coated with antibody specific for neuropeptide Y (NPY) were inserted bilaterally into the periaqueductal grey (P 0.5-1.0, LR 2.0 mm) or into the right ventrolateral medulla (3.0 mm rostral to obex; LR 3.5 mm) prior to, during and following fatiguing contractions to determine whether immunoreactive NPY was released. No release of immunoreactive NPY was detected from the site in the ventrolateral medulla. Immunoreactive NPY was released from the contralateral but not the ipsilateral periaqueductal grey during the isometric contractions, suggesting that NPY-like substances maybe involved with the integration of muscle afferent input into this area of the brainstem.

Neurons in the rat medulla oblongata containing neuropeptide Y-, angiotensin II-, or galanin-like immunoreactivity project to the parabrachial nucleus

Projections from the medulla to the parabrachial complex of the rat were examined for their content of neuropeptide Y-, angiotensin II- or galanin-like immunoreactivity using combined retrograde tracing and immunohistochemical techniques. Rhodamine-labelled latex microspheres were stereotaxically injected into discrete nuclei of the parabrachial complex. After survival of two to five days, colchicine (100 micrograms in 10 microliters saline) was injected into the cisterna magna. One day later, rats were perfused and the brainstems were prepared for visualization of the retrograde tracer and immunoreactivity of one of the three peptides. Retrograde labelling verified that the area postrema, nucleus of the tractus solitarius, caudal spinal nucleus of the trigeminal nerve, parvocellular reticular nucleus, and ventrolateral medulla including the rostral ventrolateral medulla and nucleus paragigantocellularis project to the lateral parabrachial and Kölliker-Fuse nuclei. While most projections were primarily ipsilateral, a small proportion of the projections from the ventrolateral medulla was bilateral. Neurons containing neuropeptide Y-like immunoreactivity were found in the caudal and intermediate nucleus of the tractus solitarius, dorsal to the lateral reticular nucleus and in the nucleus paragigantocellularis. After bilateral microsphere injections into the lateral parabrachial and Kölliker-Fuse nuclei, double-labelled neurons were found dorsal to the lateral reticular nucleus of caudal and intermediate medullary levels, at the ventral surface of the medulla at intermediate levels and in the nucleus paragigantocellularis at rostral levels. Neurons with angiotensin II-like immunoreactivity were observed at the dorsomedial border of the caudal and intermediate nucleus of the tractus solitarius, in the area postrema and in the lateral reticular nucleus and nucleus paragigantocellularis. Of these neurons, small numbers in the nucleus of the tractus solitarius and ventrolateral medulla also projected to the lateral parabrachial and Kölliker-Fuse nuclei. Neurons containing galanin-like immunoreactivity were found in the caudal nucleus of the tractus solitarius, the area postrema, the spinal trigeminal nucleus, the raphe nuclei (pallidus and obscurus), the nucleus paragigantocellularis and dorsal to the lateral reticular nucleus. Of these cells, double-labelled neurons were found in the commissural and medial subdivisions of the caudal nucleus of the tractus solitarius and in the rostral ventrolateral medulla including the ventral surface and the nucleus paragigantocellularis. The results suggest that neuropeptide Y, angiotensin II and galanin may serve as neurochemical messengers in pathways from the medulla to the parabrachial complex. The location of double-labelled neurons suggests that the information relayed by these neurons is related to autonomic activity.

Immunohistochemical study on the distribution of neuropeptides within the pontine tegmentum--particularly the parabrachial nuclei and the locus coeruleus of the human brain

The topographical distribution of neuropeptide-containing cell bodies, fibers and terminals was studied in human parabrachial nuclei and the pontine tegmentum with immunohistochemical stainings. Brains of seven adult human subjects of 35-72 years were fixed within 2 h post mortem. Serial sections were immunostained by antisera of 14 different neuropeptides--oxytocin, vasopressin, thyrotropin-releasing hormone, angiotensin II, calcitonin gene-related peptide, beta-endorphin, dynorphin A, dynorphin B, leucine-enkephalin, alpha-melanocyte stimulating hormone, substance P, neuropeptide Y, cholecystokinin and galanin--alternately. All of these peptides were found to be present in nerve fibers and terminals, but only two, angiotensin II and dynorphin B, in cell bodies of the parabrachial nuclei. Calcitonin gene-related peptide-, neuropeptide Y-, cholecystokinin- and galanin-immunoreactive cells were present in other areas of the pontine tegmentum, like the motor trigeminal nucleus, locus coeruleus, periventricular gray matter but not in the parabrachial nuclei. Peptidergic fibers were distributed unevenly throughout the pontine tegmentum having unique, individual distribution patterns. In the parabrachial nuclei, substance P, neuropeptide Y, cholecystokinin and galanin showed the highest density of immunoreactive neuronal networks. Moderate to low concentrations of immunoreactive processes were detected by calcitonin gene-related peptide, alpha-melanocyte stimulating hormone, dynorphin B, thyrotropin releasing hormone, leucine-enkephalin, dynorphin A, angiotensin II, beta-endorphin, vasopressin and oxytocin antisera, respectively. Other pontine tegmental areas, like the locus coeruleus, dorsal tegmental, pontine raphe and motor trigeminal nuclei as well as the central gray of the tegmental region exhibited a varying assortment of neuropeptides with distinct, individual localization patterns. Their detailed topographical distributions are mapped and given in coronal sections.

Distribution of somatostatin-28 (1-12) in the cat brainstem: an immunocytochemical study

We studied the distribution of somatostatin-28 (1-12)-immunoreactive fibers and cell bodies in the cat brainstem. A moderate density of cell bodies containing the peptide was observed in the ventral nucleus of the lateral lemniscus, accessory dorsal tegmental nucleus, retrofacial nucleus and in the lateral reticular nucleus, whereas a low density of such perikarya was found in the interpeduncular nucleus, nucleus incertus, nucleus sagulum, gigantocellular tegmental field, nucleus of the trapezoid body, nucleus praepositus hypoglosii, lateral and magnocellular tegmental fields, nucleus of the solitary tract, nucleus ambiguous and in the nucleus intercalatus. Moreover, a moderate density of somatostatin-28 (1-12)-immunoreactive processes was found in the dorsal nucleus of the raphe, dorsal tegmental nucleus, accessory dorsal tegmental nucleus, periaqueductal gray and in the marginal nucleus of the brachium conjunctivum. Finally, few immunoreactive fibers were visualized in the interpeduncular nucleus, cuneiform nucleus, locus coeruleus, nucleus incertus, superior and inferior central nuclei, nucleus sagulum, ventral nucleus of the lateral lemniscus, nucleus praepositus hypoglosii, medial vestibular nucleus, Kölliker-Fuse area, nucleus ambiguous, retrofacial nucleus, postpyramidal nucleus of the raphe, nucleus of the solitary tract, dorsal motor nucleus of the vagus, lateral reticular nucleus and laminar and alaminar spinal trigeminal nuclei.

Neuropeptide Y/angiotensin II interactions in central cardiovascular regulation of the rat

Neuropeptide Y (NPY)/angiotensin II (ANG II) interactions have been studied in the central nervous system of the rat in view of their co-distribution and their opposing role in central cardiovascular control using quantitative receptor autoradiography and measurements of mean arterial blood pressure (MAP), heart rate and respiratory rate. The receptor autoradiographical experiments show that incubation with ANG II (10 nM) produces an increase in porcine (p) iodinated NPY-(1-36) [125I]pNPY-(1-36) binding within the dorsal strip (ds) of the nucleus tractus solitarius (nTS). Immunocytochemical analysis of intracisternally injected ANG II indicated that it could reach this area, in addition to the periventricular gray of the medulla oblongata, the pons and the periventricular part of the dorsal thalamus and dentate gyrus. Furthermore, a threshold dose of ANG II given intracisternally (3 nmol/rat) together with a dose (75 pmol/rat) of pNPY-(1-36) close to its ED50 value for reducing MAP, not only counteracts the vasodepressor action of pNPY-(1-36) but also leads to a marked increase of MAP. Also the bradycardic and bradypneic actions of pNPY-(1-36) are counteracted by this dose of ANG II. In contrast, a threshold dose of pNPY-(1-36) does not counteract the pressor action of an ED50 dose of ANG II (10 nmol/rat) but even enhances the peak pressor action of ANG II. These results may be explained on the basis that central ANG II receptor activation leads to an uncoupling of the NPY Y1 receptor, which mediate the vasodepressor action of pNPY-(1-36) and which is preferentially labeled by [125I]pNPY-(1-36).(ABSTRACT TRUNCATED AT 250 WORDS)

[The nucleus tractus solitarius: neuroanatomic, neurochemical and functional aspects]

The nucleus tractus solitarii (NTS) has long been considered as the first central relay for gustatory and visceral afferent informations only. However, data obtained during the past ten years, with neuroanatomical, biochemical and electrophysiological techniques, clearly demonstrate that the NTS is a structure with a high degree of complexity, which plays, at the medullary level, a key role in several integrative processes. The NTS, located in the dorsomedial medulla, is a structure of small size containing a limited number of neurons scattered in a more or less dense fibrillar plexus. The distribution and the organization of both the cells and the fibrillar network are not homogeneous within the nucleus and the NTS has been divided cytoarchitectonically into various subnuclei, which are partly correlated with the areas of projection of peripheral afferent endings. At the ultrastructural level, the NTS shows several complex synaptic arrangements in form of glomeruli. These arrangements provide morphological substrates for complex mechanisms of intercellular communication within the NTS. The NTS is not only the site of vagal and glossopharyngeal afferent projections, it receives also endings from facial and trigeminal nerves as well as from some renal afferents. Gustatory and somatic afferents from the oropharyngeal region project with a crude somatotopy within the rostral part of the NTS and visceral afferents from cardiovascular, digestive, respiratory and renal systems terminate viscero-topically within its caudal part. Moreover the NTS is extensively connected with several central structures. It projects directly to multiple brain regions by means of short connections to bulbo-ponto-mesencephalic structures (parabrachial nucleus, motor nuclei of several cranial nerves, ventro-lateral reticular formation, raphe nuclei...) and long connections to the spinal cord and diencephalic and telencephalic structures, in particular the hypothalamus and some limbic structures. The NTS is also the recipient of several central afferent inputs. It is worth to note that most of the structures that receive a direct projection from the NTS project back to the nucleus. Direct projections from the cerebral cortex to the NTS have also been identified. These extensive connections indicate that the NTS is a key structure for autonomic and neuroendocrine functions as well as for integration of somatic and autonomic responses in certain behaviors. The NTS contains a great diversity of neuroactive substances. Indeed, most of the substances identified within the central nervous system have also been detected in the NTS and may act, at this level, as classical transmitters and/or neuromodulators.(ABSTRACT TRUNCATED AT 400 WORDS)

Coerulospinal cells containing neuropeptide Y in the cat

Spinally projecting neuropeptide Y (NPY)-immunoreactive cells were sought in the feline locus coeruleus (LC) nuclear complex after horseradish peroxidase (HRP) injection into the lumbar cord; HRP injection was followed by intracerebroventricular colchicine administration. Our results revealed that a significant number (approximately 20% of all descending cells from the LC complex) of spinally projecting NPY-immunoreactive neurons arise from the LC alpha, the subcoeruleus and the Kölliker-Fuse nuclei. Other nonspinally projecting NPY-containing cells were also evident in the laterodorsal tegmental nucleus and the LCd, in addition to those occurring in the aforementioned LC nuclear complex.

An intracellular study of respiratory neurons in the rostral ventrolateral medulla of the rat and their relationship to catecholamine-containing neurons

Intracellular recording and labelling with Lucifer yellow of respiratory neurons in the rostral ventrolateral medulla were carried out in urethane-anaesthetised rats. A combined immunofluorescence and immunoperoxidase technique enabled an assessment of the tyrosine hydroxylase immunoreactivity, as well as an examination of the morphology of inspiratory and expiratory neurons in this part of the medulla oblongata. The results demonstrate: a) that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine-containing neurons of the C1 cell group, but are not themselves catecholamine-containing; b) that many non-spinally projecting respiratory neurons have axonal arborisations within the ventrolateral medulla in the same region as the C1 cell group, other respiratory neurons, and neurons reported to have a cardiovascular function; and c) that the dendrites of respiratory neurons in this region radiate throughout the ventrolateral medulla and frequently approach the ventral surface.

Distribution of neuropeptide Y-like immunoreactive cell bodies and fibers in the brain stem of the cat

By using intratissue injections of colchicine and an indirect immunoperoxidase technique, we studied the distribution of cell bodies and fibers containing neuropeptide Y-like immunoreactivity in the brain stem of the cat. The densest clusters of immunoreactive perikarya were observed in the following nuclei: anteroventral cochlear, lateral reticular (internal and external divisions), dorsal tegmental, inferior colliculus and dorsal nucleus of the lateral lemniscus. By contrast, the nuclei abducens, the nucleus of the trapezoid body, preolivary, interpeduncularis, infratrigeminal, gigantocellular tegmental field, coeruleus and dorsal motor nucleus of the vagus had the lowest density. Finally, a moderate density of neuropeptide Y-like immunoreactive cell bodies was found in the nuclei: lateral tegmental field, laminar spinal trigeminal, praepositus hypoglossi, superior colliculus, lateral vestibular and motor trigeminal. In addition, a mapping of the neuropeptide Y-like immunoreactive fibers was carried out. Thus, the densest network of immunoreactive fibers was observed in the laminar spinal trigeminal nucleus. The nuclei periaqueductal gray, inferior central, praepositus hypoglossi, postpyramidal raphe, dorsal raphe, incertus and medial vestibular contained a moderate density of immunoreactive fibers, whereas the nuclei interpeduncularis, inferior colliculus, superior central, gracile, retrorubral, Kölliker-Fuse, dorsal tegmental, ambiguus and alaminar spinal trigeminal had the lowest density of neuropeptide Y-like immunoreactive fibers. The anatomical location of neuropeptide Y-like immunoreactivity suggests that the peptide could play an important role in several physiological functions, e.g., those involved in cardiovascular, auditory, motor, visual, nociceptive and somatosensory mechanisms.