Search

In this study, we demonstrate the presence of immunoreactive structures containing calcitonin gene-related peptide in the alpaca brainstem. This is the first time that a detailed mapping of the cell bodies and fibers containing this neuropeptide in the alpaca brainstem has been carried out using an immunocytochemical technique. Immunoreactive cell bodies and fibers were widely distributed throughout the alpaca brainstem. A high density of calcitonin gene-related peptide-immunoreactive perikarya was found in the superior colliculus, the dorsal nucleus of the raphe, the trochlear nucleus, the lateral division of the marginal nucleus of the brachium conjunctivum, the motor trigeminal nucleus, the facial nucleus, the pons reticular formation, the retrofacial nucleus, the rostral hypoglossal nucleus, and in the motor dorsal nucleus of the vagus, whereas a high density of fibers containing calcitonin gene-related peptide was observed in the lateral division of the marginal nucleus of the brachium conjunctivum, the parvocellular division of the alaminar spinal trigeminal nucleus, the external cuneate nucleus, the nucleus of the solitary tract, the laminar spinal trigeminal nucleus, and in the area postrema. This widespread distribution indicates that the neuropeptide studied might be involved in multiple functions in the alpaca brainstem.

Using an indirect immunoperoxidase technique, the location of cell bodies and fibers containing substance P, neurokinin A and neurokinin B was studied in the cat spinal cord. The former two neuropeptides showed a widespread distribution throughout the whole spinal cord, whereas the distribution of neurokinin B was more restricted. Neurokinin A-immunoreactive structures showed a more widespread distribution and a higher density than the immunoreactive structures observed to contain substance P. In the cat spinal cord, we observed cell bodies containing neurokinin A, but no cell bodies containing neurokinin B or substance P were found. These cell bodies were located in laminae V (sacral 1 and 2 levels), VI (sacral 1 and 3), VII (lumbar 7, sacral 1 and 3, caudal 1) and X (sacral 1). Laminae I and II showed the highest density of immunoreactive fibers for each of the three tachykinins studied, being in general lamina IV who showed the lowest number of immunoreactive fibers containing substance P, neurokinin A or B. The anatomical distribution of the three tachykinins studied in the cat spinal cord indicates that the neuropeptides could be involved in the neurotransmission and/or in the neuromodulation of nociceptive information, as well as in autonomic and affective responses to pain. Moreover, the involvement of substance P, neurokinin A or B in other functions unrelated to the transmission of pain is also possible (autonomic and motor functions). The distribution of the neuropeptides studied in the cat is compared with the location of the same neuropeptides in the spinal cord of other species. The possible origin of the tachykinergic fibers in the cat spinal cord is also discussed.

Using an indirect immunoperoxidase technique, the localization of somatostatin-28 (1-12)-like immunoreactive fibers and cell bodies in the auditory cortex of the cat (anterior, primary, secondary, temporal, ventral, ventroposterior, posterior and dorsoposterior auditory fields) was studied. In general, the distribution of SOM-ir structures is widespread in the auditory cortex of the feline. A high density of immunoreactive fibers as well as a low density of cell bodies containing somatostatin were observed in all the layers of the eight above-mentioned auditory fields. These data indicate that somatostatin-28 (1-12) could act as a neurotransmitter and/or a neuromodulator in the auditory cortex of the cat. The origin of the SOM-ir fibers in the auditory cortex of the cat, as well as the issue of whether the cell bodies containing somatostatin-28 (1-12) are local or projecting neurons is discussed.

Dopamine is one of the principal neurotransmitters in the basal ganglia, where it plays a critical role in motor control and cognitive function through its interactions with the specific dopamine receptors D1 to D5. Although the activities mediated by most dopamine receptor subtypes have already been determined, the role of the D5 receptor subtype in the basal ganglia has still not been established. Furthermore, it is often difficult to distinguish between dopamine D5 and D1 receptors as they are stimulated by the same ligands, and they have a similar molecular structure and pharmacology. In an effort to understand the differences between these two receptor subtypes, we have studied the distribution of neurons containing D5 receptors in the striatum, and their molecular phenotype. As a result, we show that the D5 receptor subtype is present in two different populations of striatal neurons, projection neurons and interneurons. Overall, the abundance of this receptor subtype in the striatum is low, particularly in striatal projection neurons of both the direct and indirect projection pathways. In contrast, the expression of D5 receptors in striatal interneurons (cholinergic, somatostatin- or parvalbumin-positive neurons) is high, while low to moderate expression was observed in calretinin-positive neurons. Our results demonstrate the presence of D5 receptors in all the striatal cell populations so far described, although at different intensities in each. The fact that a large number of striatal neurons express the D5 receptor subtype suggests that this receptor fulfils an important function in the process of integrating information in the striatum.

The present study investigated the neurotensin (NT) receptor subtype (NTR) involved in the antagonistic neurotensin modulation of striatal dopamine D2 receptors observed in vitro and in vivo. The NT induced increase of the IC50 values of dopamine (DA) competition for [125I]iodosulpiride binding sites was counteracted by the NTR1-like antagonist SR48692 in rat striatal slices. Intrastriatal perfusion of pergolide induced in the awake rat an inhibition of striatal DA release that was antagonized by NT. This action of NT was counteracted by co-perfusion with the NTR1 like antagonist SR48692. These data indicate that there exists in the striatum at the prejunctional level an intramembrane antagonistic NT receptor/DA D2 receptor-receptor interaction where NTR1 like receptor activation reduces the DA D2 autoreceptor function.

The effect of an acute administration of the vigilance-promoting drug modafinil ((+/-)(diphenyl-methyl)-sulfinyl-2 acetamide; Modiodal) on the nigrostriatal dopamine system was studied after damage induced by MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) by means of immunohistochemistry for tyrosine hydroxylase (TH) and a stereological method. MPTP (40 mg/kg) reduced from 24,380 +/- 902 to 13,501 +/- 522 and from 37,868 +/- 3300 to 20,568 +/- 1270, respectively, the number of TH immunoreactive (IR) and non-TH IR nigral neurons. Co-administration of Modafinil restored to normal the number of these neuronal populations. MPTP treatment induced also a reduction in the volume of TH IR neurons, which was counteracted by Modafinil administration. The data provide morphological evidence, based on unbiased stereological analysis, for a potential neuroprotective role of Modafinil, not only in dopaminergic neurons, but also with a similar magnitude in the non-DA nerve cell population of the substantia nigra after MPTP lesion. These results suggest that Modafinil has a neuroprotective role in the substantia nigra via a still undefined mechanism in which a crucial role of DA uptake blockade should be excluded. Modafinil may therefore have a therapeutic potential in neurodegenerative processes such as those occurring in Parkinson's disease.

Neuronal c-Fos protein-like immunoreactivity (c-Fos IR) in parts of the nucleus tractus solitarii (NTS)-dorsal motor nucleus of the vagus nerve (dmnX) complex of the anaesthetized rat was studied 90 min after NTS microinjections of neuropeptide Y (NPY) and/or adrenergic receptor agonists in relevant cardiovascular doses. Microinjections of NPY and l-adrenaline alone into the NTS induced neuronal c-Fos IR in parts of the NTS-dmnX complex, while clonidine had no action. No double-labelled GFAP/c-Fos immunoreactive cells were found in the NTS-dmnX complex after the microinjection of NPY into the NTS. Coinjections of NPY and l-adrenaline or clonidine into the NTS reduced the NPY-induced increase in c-Fos IR. The results emphasize that during cardiovascular regulation NPY receptors can control neuronal gene expression in the NTS-dmnX complex via c-fos and that stimulation of alpha 2-adrenoceptors can attenuate NPY receptor transduction also in terms of induction of c-Fos IR in the NTS-dmnX complex via an antagonistic alpha 2/NPY receptor interaction.

Using an indirect immunoperoxidase technique, the location of gastrin-releasing/bombesin-like immunoreactive fibres and cell bodies in the cat brainstem was studied. A moderate or low density of immunoreactive cell bodies was observed in the nucleus of the brachium of the inferior colliculus, pericentral nucleus of the inferior colliculus, ventral nucleus of the lateral lemniscus and in the external division of the lateral reticular nucleus. The densest network of immunoreactive fibres was visualized in the interpeduncular nucleus, marginal nucleus of the brachium conjunctivum, alaminar and laminar spinal trigeminal nuclei and in the substantia nigra. The periaqueductal gray, brachium of the inferior colliculus, nucleus of the brachium of the inferior colliculus, locus coeruleus, nucleus incertus, Kölliker-Fuse nucleus, facial nucleus, medial nucleus of the solitary tract and the area postrema contained a moderate density of immunoreactive fibres, whereas the pericentral nucleus of the inferior colliculus, nucleus sagulum, cuneiform nucleus, dorsal nucleus of the raphe, superior central nucleus, central, lateral and paralemniscal tegmental fields, ventral nucleus of the lateral lemniscus, dorsal tegmental nucleus, postpyramidal nucleus of the raphe, nucleus ambiguus, accessory dorsal tegmental nucleus, dorsal motor nucleus of the vagus and the inferior olive had the lowest density of immunoreactive fibres.

We have studied the distribution of neurokinin A-like immunoreactive cell bodies and fibers in the cat brainstem. The densest clusters of perikarya containing the peptide were observed in the periaqueductal gray, inferior colliculus, postpyramidal nucleus of the raphe, medial nucleus of the solitary tract and in the lateral reticular nucleus. By contrast, the interpeduncular nucleus, magnocellular part of the red nucleus, central tegmental field, cuneiform nucleus, dorsal tegmental nucleus, nucleus sagulum and the medial and inferior vestibular nuclei had the lowest density, whereas a moderate density of immunoreactive cell bodies was found in the superior colliculus, medial division of the dorsal nucleus of the raphe, nucleus incertus, locus coeruleus and in the Kölliker-Fuse area. The highest density of immunoreactive fibers was observed in the substantia nigra, periaqueductal gray, marginal nucleus of the brachium conjunctivum, medial vestibular nucleus, medial nucleus of the solitary tract, laminar spinal trigeminal nucleus, inferior colliculus, medial division of the dorsal nucleus of the raphe, locus coeruleus, dorsal tegmental nucleus and in the spinal trigeminal tract. A moderate density of immunoreactive fibers was found in the dorsal motor nucleus of the vagus and in the postpyramidal nucleus of the raphe and a low density in the cuneiform nucleus, Kölliker-Fuse area, nucleus sagulum, inferior and superior central nuclei, lateral reticular nucleus and in the lateral and magnocellular tegmental fields.

We have studied the induction of c-fos immunoreactivity (c-fos IR) in catecholaminergic and vasopressinergic immunoreactive neurons after repeated phosphate-buffered saline (PBS) loading or after repeated elicitation of the baroreceptor reflex via repeated infusion of the vasoconstrictor agent L-phenylephrine. About 75% and 30%, respectively, of the tyrosine-hydroxylase immunoreactive (IR) cell bodies of the ventral noradrenaline (NA) A1/adrenaline (A) C1 and dorsal NA A2/A C2 areas and 60% and 30%, respectively, of the phenylethanolamine N-methyltransferase IR nerve cells of the adrenaline C1 and C2 areas and 25% of the vasopressin (VP) IR neurons of the supraoptic (SO) nucleus developed nuclear c-fos IR after repeated PBS loading. This phenomenon remained unaltered by the repeated elicitation of the baroreceptor reflex. These results suggest that the activation of volume receptors promotes homeostatic responses via activation of early genes in subsets of central medullary noradrenaline and adrenaline neurons and SO VP neurons of the urethane-anaesthetized rat.

Using an indirect immunoperoxidase technique, the location of somatostatin-28 (1-12)-like immunoreactive fibres and cell bodies in the cat diencephalon was studied. The hypothalamus was richer in somatostatin-28 (1-12)-like immunoreactive structures than the thalamus. A high density of immunoreactive fibres was observed in the nuclei habenularis lateralis, paraventricularis anterior (its caudal part), filiformis, hypothalami ventromedialis, and regio praeoptica, whereas a moderate density was found in the nuclei paracentralis, supraopticus, supra chiasmaticus, hypothalamus posterior and area hypothalamica dorsalis. The nuclei lateralis dorsalis, lateralis posterior, medialis dorsalis, rhomboidens, centralis medialis, ventralis medialis, reuniens, anterior dorsalis, parataenialis, interanteromedialis, hypothalamus lateralis, hypothalamus dorsomedialis and arcuatus had the lowest density of immunoreactive fibres. In addition, a high or moderate density of somatostatin-28 (1-12)-like immunoreactive cell bodies was observed in the nuclei paraventricularis hypothalami, supraopticus, supra chiasmaticus, area hypothalamics dorsalis, subparafascicularis, hypothalamus posterior and hypothalamus anterior, whereas scarce immunoreactive perikarya were visualized in the nuclei lateralis dorsalis and parafascicularis. The distribution of somatostatin-28 (1-12)-like immunoreactive structures is compared with the location of other neuropeptides in the cat diencephalon.

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.