Immunocytochemical study of Met-enkephalin-like cell bodies in the cat hypothalamus

Distribution of met-enkephalin immunoreactivity in the diencephalon and the brainstem of the dog

The endogenous opioid system, in particular the enkephalins, has been implicated in a vast array of neurological functions. The dog could be a suitable model for the study of complex interactions between behavioral state and regulatory physiology in which the opioid system appeared to be implicated. Moreover, opiate derivatives are currently used in veterinary clinic and sometimes pharmacologically tested in the dog. However, there are no anatomical data regarding the organization of the opioid system in this species. The present work represents the first attempt to map the distribution of Met(5)-enkephalin-like-immunoreactive (Met-enk-li) cell bodies and fibers in the diencephalon and the brainstem of the dog. In the diencephalon, labeled cells were present in all the mid-line and intralaminar thalamic nuclei; the lateral posterior, pulvinar and suprageniculate nuclei; the ventral nucleus of the lateral geniculate body and the medial geniculate body. Additionally, Met-enk-li cells were seen in every hypothalamic nucleus except in the supraoptic. Variable densities of labeled fibers were also seen in all these nuclei except in the medial geniculate body and in most areas of the lateral posterior and pulvinar nuclei. In the mesencephalon, positive cells were found in the periaqueductal gray, the Edinger-Westphal and interpeduncular nuclei, delimited areas of the superior and inferior colliculi and the ventral tegmental area. In the rhombencephalon, labeled cells were seen in the majority of the nuclei in the latero-dorsal pontine tegmentum, the nuclei of the lateral lemniscus, the trapezoid, vestibular medial, vestibular inferior and cochlear nuclei, the prepositus hypoglossal, the nucleus of the solitary tract and the dorsal motor nucleus of the vagus, the infratrigeminal nucleus and the caudal part of the spinal trigeminal nucleus and in the rhombencephalic reticular formation. The distribution of fibers included additionally the substantia nigra, all the trigeminal nerve nuclei, the facial nucleus and a restricted portion of the inferior olive. These results are discussed with regard to previous reports on the distribution of Met-enk in other species.

An immunocytochemical mapping of beta-endorphin (1-27) in the cat diencephalon

The distribution of beta-endorphin (1-27) immunoreactive cell bodies and fibres was studied in the diencephalon of the cat using an indirect immunoperoxidase technique. In the thalamus, almost all the immunoreactive fibres were found in the midline region and in nuclei located near the midline, whereas in the hypothalamus fibres containing beta-endorphin (1-27) were visualized extending by the whole structure. The hypothalamus showed a higher density of beta-endorphin (1-27) immunoreactive fibres than the thalamus, as well as immunoreactive cell bodies, since in the thalamus no beta-endorphin (1-27) immunoreactive neuron was located. The densest network of immunoreactive fibres was observed in the epithalamus (nucleus periventricularis anterior) and in the hypothalamic nuclei arcuatus, hypothalami ventromedialis, suprachiasmaticus, periventricularis hypothalami, hypothalamus dorsomedialis, area hypothalamica dorsalis, hypothalamus anterior, filiformis, hypothalamus posterior and regio praeoptica. In the hypothalamus, a high density of perikarya containing beta-endorphin (1-27) was observed in the nucleus arcuatus and a low density in the nucleus hypothalami ventromedialis. The distribution of beta-endorphin (1-27) immunoreactive fibres and perikarya is compared with the location of other neuropeptides in the cat diencephalon. Our findings reveal that b-endorphin (1-27) immunoreactive structures are widely distributed in the cat diencephalon, suggesting that the peptide might be involved in several physiological functions.

Proenkephalin gene regulation in the neuroendocrine hypothalamus: a model of gene regulation in the CNS

During the past decade, a great deal of progress has been made in studying the mechanisms by which transcription of neuropeptides is regulated by second messengers and neural activity. Such investigations, which have depended to a great extent on the use of transformed cell lines, are far from complete. Yet a major challenge for the coming decade is to understand the regulation of neuropeptide genes by physiologically and pharmacologically relevant stimuli in appropriate cell types in vivo. The proenkephalin gene, a member of the opioid gene family, has served as a model to study regulated transcription, not only in cell lines, but also in central (e.g., hypothalamic) and peripheral (e.g., adrenal) neuroendocrine tissues. Here we review regulation of proenkephalin gene expression in the hypothalamus. Several approaches, including in situ hybridization, use of transgenic mice, and the adaptation of electrophoretic mobility shift assays to complex tissues, have played critical roles in recent advances. A summary of possible future developments in this field of research is also presented.

Distribution of neurokinin A in the cat diencephalon: an immunocytochemical study

The distribution of neurokinin A-like immunoreactive cell bodies and fibers in the diencephalon of the cat was studied using an indirect immunoperoxidase technique. A high or moderate density of immunoreactive neurons was observed in the nuclei habenularis lateralis, medialis dorsalis, parafascicularis, hypothalamus posterior, area hypothalamica dorsalis, hypothalamus lateralis, periventricularis hypothalami, above the corpus mamillare, and in the perifornical area, whereas scarce immunoreactive perikarya were visualized in the nuclei reuniens, hypothalami ventromedialis, hypothalamus dorsomedialis, and mamillaris lateralis. The highest density of fibers containing neurokinin A was found in the nuclei periventricularis anterior, rhomboidens, centralis medialis, periventricularis hypothalami, and supraopticus. In the regio praeoptica, area hypothalamica dorsalis, hypothalamus posterior, and in the perifornical area a moderate density of immunoreactive fibers was observed, whereas the nuclei habenularis lateralis, medialis dorsalis, mamillaris lateralis, parataenialis, reuniens, habenularis medialis, filiformis, hypothalamus dorsomedialis, hypothalami ventromedialis, arcuatus, and suprachiasmaticus showed a low density of neurokinin A immunoreactive fibers.

Somatostatin-28 (1-12)-like immunoreactivity in the cat diencephalon

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.

Neurotensin-like immunoreactivity in the diencephalon of the adult male cat

Using an indirect immunoperoxidase technique, the location of neurotensin-like fibers and cell bodies was studied in the diencephalon of the cat. The findings showed that the hypothalamus is richer in neurotensin-like-immunoreactive structures than the thalamus, and that neurotensin-like-immunoreactive structures are more widely distributed in the hypothalamus than in the thalamus. A high density of immunoreactive fibers was observed in the hypothalamic regions, area hypothalamica dorsalis, hypothalamus posterior, nucleus (n.) filiformis and n. arcuatus, whereas a moderate density was found in the n. parafascicularis, n. paraventricularis anterior, hypothalamus lateralis, median eminence and n. paraventricularis hypothalami. Other diencephalic regions such as n. lateralis posterior, n. lateralis dorsalis, n. medialis dorsalis, n. habenularis lateralis, n. centrum medianum, n. rhomboidens, n. reuniens, hypothalamus anterior, n. supra chiasmaticus, hypothalamus ventromedialis, n. supraopticus and hypothalamus dorsomedialis had the lowest density of immunoreactive fibers. In addition, the densest clusters of neurotensin-like perikarya were found in the n. arcuatus, n. centralis medialis and hypothalamus posterior, whereas the n. medialis dorsalis, n. paraventricularis anterior, n. reuniens, hypothalamus lateralis and hypothalamus ventromedialis had the lowest density. In the n. lateralis dorsalis, n. supraopticus, area hypothalamica dorsalis and n. supra chiasmaticus the density of immunoreactive perikarya was moderate.

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.

Immunocytochemical study of enkephalin-like cell bodies in the thalamus of the rat

The distribution of enkephalin-like cell bodies in the thalamus of the rat was studied by means of intratissular injections of colchicine and using an indirect immunoperoxidase technique. The densest clusters of immunoreactive perikarya were observed in the nuclei geniculatum lateralis ventralis, medialis dorsalis, centralis lateralis, centralis medialis and anterior ventralis. Whereas the nuclei praetectalis lateralis, lateralis posterior, habenularis lateralis, parataenialis (its caudal part), parafascicularis, centrum medianum, reuniens and ventralis medialis had the lowest density. In other thalamic nuclei geniculatum mediale, paraventricularis and parataenialis (its rostral part) the density of enkephalin-like cell bodies was intermediate. These results suggest that the intratissular injection of colchicine is the better way of administration of the drug in order to study the distribution of peptidergic cell bodies in the mammalian CNS. The similarities and differences found in the distribution of enkephalinergic cell populations in the thalamus of different mammals are discussed.

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

The distribution of fibres and cell bodies containing neuropeptide Y-like immunoreactivity in respiratory nuclei of the brain stem was studied using an indirect immunoperoxidase technique. In order to visualize immunoreactive perikarya, intraventricular or intratissue injections of colchicine were carried out. The richest cluster of immunoreactive perikarya was localized in the Bötzinger complex, whereas in the nuclei ambiguus, retroambiguus, parabrachialis medialis and Kölliker-Fuse area, a moderate density of cell bodies was observed. The ventrolateral subnucleus of the nucleus tractus solitarii had the lowest number of immunoreactive neurons. Neuropeptide Y-like immunoreactive fibres were abundant in the Kölliker-Fuse area, and scarce in the nuclei ambiguus, parabrachialis medialis and Kölliker-Fuse area. A moderate network of immunoreactive fibres was observed in the nuclei retroambiguus and the ventrolateral subnucleus of the nucleus tractus solitarii. The presence of neuropeptide Y-like immunoreactive areas suggests a role for this peptide in the control of respiratory mechanisms. Alternatively such a cluster of cell bodies and fibre networks might be also related with neighbouring cardiovascular control areas.

Immunocytochemical study of angiotensin-II fibres and cell bodies in the brainstem respiratory areas of the cat

The distribution of fibres and cell bodies containing angiotensin-II in brainstem respiratory nuclei was studied using an indirect immunoperoxidase technique. In order to visualize immunoreactive perikarya, intracerebral injections of colchicine were carried out. The richest cluster of immunoreactive perikarya was localized in the Bötzinger complex and Kölliker-Fuse areas, whereas in the nucleus ambiguus and nucleus retroambiguus a moderate density of cell bodies was observed. The nucleus tractus solitarius (ventrolateral portion) and the nucleus parabrachialis medialis had the lowest number of immunoreactive neurons. Angiotensin-II containing fibres were abundant in the nucleus parabrachialis medialis, Bötzinger complex and Kölliker-Fuse area, and scarce in the nuclei tractus solitarius (ventrolateral part), ambiguus and retroambiguus. Moreover, in the dorsal motor nucleus of the vagus a dense network of immunoreactive fibres and a large number of cell bodies were observed. The presence of angiotensin-II in respiratory areas suggests a role for this octapeptide in controlling respiration.

Immunocytochemical study of angiotensin II cell bodies in the rat thalamus

The distribution of angiotensin II cell bodies in the thalamus of the rat was studied by means of intratissue injections of colchicine and using an indirect immunoperoxidase technique. The densest clusters of immunoreactive perikarya were observed in the nuclei geniculatum laterale, medialis dorsalis, ventralis posterior, centralis lateralis, centralis medialis and anterior dorsalis, whereas the nuclei lateralis posterior, lateralis and geniculatum laterale dorsalis had the lowest density. In other thalamic nuclei, geniculatum mediale, lateralis anterior, paraventricularis and ventralis medialis, the density of angiotensin II cell bodies was intermediate. In all these thalamic nuclei, small, round immunoreactive cells with short processes were observed.