Folic acid in the monkey brain: an immunocytochemical study

The present report describes the first visualization of folic acid-immunoreactive fibers in the mammalian central nervous system using a highly specific antiserum directed against this vitamin. The distribution of folic acid-immunoreactive structures was studied in the brainstem and thalamus of the monkey using an indirect immunoperoxidase technique. We observed fibers containing folic acid, but no folic acid-immunoreactive cell bodies were found. In the brainstem, no immunoreactive structures were visualized in the medulla oblongata, pons, or in the medial-caudal mesencephalon, since at this location immunoreactive fibers containing folic acid were only found at the rostral level in the dorsolateral mesencephalon (in the mesencephalic-diencephalic junction). In the thalamus, the distribution of folic acid-immunoreactive structures was more widespread. Thus, we found immunoreactive fibers in the midline, in nuclei close to the midline (dorsomedial nucleus, centrum medianum/parafascicular complex), in the ventral region of the thalamus (ventral posteroinferior nucleus, ventral posteromedial nucleus), in the ventrolateral thalamus (medial geniculate nucleus, lateral geniculate nucleus, inferior pulvinar nucleus) and in the dorsolateral thalamus (lateral posterior nucleus, pulvinar nucleus). The highest density of fibers containing folic acid was observed in the dorsolateral mesencephalon and in the pulvinar nucleus. The distribution of folic acid-immunoreactive structures in the monkey brain suggests that this vitamin could be involved in several mechanisms, such as visual, auditory, motor and somatosensorial functions.

Distribution of ACTH immunoreactivity in the diencephalon and the brainstem of the dog

The present work describes for the first time the anatomical distribution of adrenocorticotropic hormone (ACTH) in the diencephalon and the brainstem of the dog by means of the indirect immunoperoxidase technique. The distribution found in this species agrees well with the pattern found in other mammals and particularly confirms much of the findings reported in the cat. An exception to that concordance is the presence of ACTH perikarya in the nucleus of the solitary tract of the dog, a population that has been described in the rat but not in the cat, and in the ventral mesencephalon. This last population spread across the ventral tegmental area from the raphe to the cerebral peduncle and appeared to be a specific feature of the canine brain. On the other hand, we can not see ACTH fibers in the substantia nigra of the dog which could be a characteristic of the domestic carnivores, opposite to rodents, since these fibers appeared to be also lacking in the cat. Nevertheless, the widespread distribution of ACTH fibers in the brain of the dog included many other nuclei containing monoaminergic neurons which supported a possible role for ACTH in the regulation of these neurotransmitter systems.

Antitumoural action of L-733,060 on neuroblastoma and glioma cell lines

We have performed an in vitro study of the growth-inhibitory capacity of the potent and long-acting NK1 receptor antagonist L-733,060, at concentrations ranging from 2.5 microM to 20 microM, against the neuroblastoma cell line SKN-BE(2) and 10 microM to 25 microM for glioma cell line GAMG. Coulter counter was used to determine viable cell numbers, followed by application of the tetrazolium compound [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)2-(4-sulfophenyl)-2H-tetrazolium], inner salt colorimetric method to evaluate cell viability in this cytotoxicity assay. L-733,060 inhibited the growth of the two cell lines studied in a dose-dependent manner. The IC 50 values were 11.6 microM (30h) and 10.2 microM (72h) for SKN-BE(2); and 21.3 microM (48h) and 19.9 microM (96h) for GAMG. These findings indicate that the NK1 receptor antagonist L-733,060 acts as a broad-spectrum antitumoural agent. This new action, reported here for the first time, suggests that the NK1 receptor antagonist L-733,060 could be a promising therapeutic drug for the treatment of human neuroblastoma and human glioma.

Immunocytochemical distribution of Met-enkephalin-Arg6-Gly7-Leu8 (Met-8) in the auditory system of the rat

Methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) (Met(8)) is known to act as a neurotransmitter or neuromodulator and it has been implicated in pain, cardiovascular and motor mechanisms, but its role in audition is currently unknown. In the present study we have applied an immunocytochemical technique and describe the distribution of cell bodies and fibers containing Met(8) in the auditory pathway of the rat. The main finding is that we found either Met(8)-immunoreactive fibers or cell bodies or both in virtually all nuclei of the rat auditory system except for the medial superior olive and the ventral division of the medial geniculate body in which we did not find any immunoreactivity for Met(8). This suggests that the neuropeptide Met(8) is widely distributed throughout the auditory system of the rat. Our results suggest that Met(8) could play at least two roles in hearing. It seems to be involved in the processing of the descending auditory pathway, and it may be implicated in the multisensory integration of auditory information that takes place in the non-lemniscal auditory pathway.

An immunocytochemical mapping of methionine-enkephalin-arg6-gly7-leu8 in the human brainstem

Using an indirect immunoperoxidase technique, we studied the distribution of immunoreactive fibers and cell bodies containing methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) in the adult human brainstem. Immunoreactive cell bodies were found in the reticular formation of the medulla oblongata (in which we observed the highest density of immunoreactive cell bodies) and the pons, the solitary nucleus, the hypoglossal nucleus, the medial and spinal vestibular nuclei, the lateral cuneate nucleus, the nucleus prepositus, the central gray of the pons and mesencephalon, the central and pericentral nuclei of the inferior colliculus, the superior colliculus, ventral to the superior olive and in the midline region of the pons and mesencephalon. The highest density of immunoreactive fibers containing methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) was found in the spinal trigeminal nucleus, the central gray and the reticular formation of the medulla oblongata, pons and mesencephalon, the solitary nucleus, the spinal vestibular nucleus, the dorsal accessory olivary nucleus, the raphe obscurus, the substantia nigra and in the interpeduncular nucleus. The widespread distribution of immunoreactive structures containing methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) in the human brainstem indicates that this neuropeptide might be involved in several physiological mechanisms, acting as a neurotransmitter and/or neuromodulator.

An immunocytochemical mapping of somatostatin in the cat auditory cortex

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.

Angiotensin II modulates the cardiovascular responses to microinjection of NPY Y1 and NPY Y2 receptor agonists into the nucleus tractus solitarii of the rat

The aim of this work was to investigate the modulation of the cardiovascular effects of neuropeptide Y (NPY) in the nucleus tractus solitarii (NTS) by angiotensin II (Ang II) and to determine the NPY receptor subtype involved in this modulation. Anesthesized Sprague-Dawley rats received microinjections in the NTS of Ang II (threshold and ED(50) doses) with NPY Y(1) agonist Leu(31)Pro(34)NPY and NPY Y(2) agonist NPY(13-36) (threshold and ED(50) doses). The changes in mean arterial pressure (MAP) and heart rate (HR) recorded in the femoral artery were analyzed during 60 min after the microinjections. The injection of threshold doses of Ang II, Y(1) agonist or Y(2) agonist alone did not produce any change in cardiovascular parameters. However, the co-injections into the NTS of threshold doses of both Ang II and the Y(1) agonist elicited significant increases of MAP and HR of about 12 and 10%, respectively. The co-administration of threshold doses of Ang II with the Y(2) agonist also induced a significant vasopressor response. The vasodepressor and bradycardiac effect of an ED(50) dose of the Y(1) agonist was significantly counteracted (P<0.01) by a threshold dose of Ang II. The vasopressor effect elicited by an ED(50) dose of the Y(2) agonist was significantly enhanced by a threshold dose of Ang II (P<0.01). No significant change of cardiovascular responses elicited by an ED(50) dose of Ang II was observed in the presence of threshold doses of the Y(1) agonist or of the Y(2) agonist. The present study gives functional evidences for a differential modulatory activity of Ang II on the cardiovascular responses mediated by Y(1) and Y(2) receptor subtypes, which may be of relevance for central cardiovascular regulation in the NTS.

An immunocytochemical mapping of methionine-enkephalin-Arg6-Gly7-Leu8 in the cat brainstem

The distribution of methionine-enkephalin-Arg6-Gly7-Leu8-immunoreactive cell bodies and fibres was studied in the brainstem of the cat using an indirect immunoperoxidase technique. In the mesencephalon, immunoreactive cell bodies were observed in the periaqueductal grey, the dorsal raphe nucleus, the central and pericentral nuclei of the inferior colliculus and the pericentral division of the dorsal tegmental nucleus. In the pons, immunoreactive cell bodies were observed in the dorsolateral division of the pontine nucleus; below the central division of the dorsal tegmental nucleus; above the dorsolateral division of the pontine nucleus, and close to the superior cerebellar peduncle. In the medulla oblongata, immunoreactive cell bodies were observed in the laminar spinal trigeminal nucleus and in the lateral tegmental field; the dorsal motor nucleus of the vagus; the prepositus hypoglossal nucleus; the medial nucleus of the solitary tract; the rostral division of the cuneate nucleus, and close to the parvocellular division of the alaminar spinal trigeminal nucleus. The highest (moderate) density of immunoreactive fibres was observed in the periaqueductal grey; the parvocellular and magnocellular divisions of the alaminar spinal trigeminal nucleus; the laminar spinal trigeminal nucleus; the rostral division of the cuneate nucleus; the dorsal motor nucleus of the vagus; the lateral nucleus of the solitary tract, and in the midline between the central divisions of the reticulotegmental pontine nucleus. The widespread distribution of methionine-enkephalin-Arg6-Gly7-Leu8 in the cat brainstem indicates that the peptide might be involved in several physiological functions.

Mapping of neurokinin-like immunoreactivity in the human brainstem

BACKGROUND

Using an indirect immunoperoxidase technique, we have studied the distribution of immunoreactive fibers and cell bodies containing neurokinin in the adult human brainstem with no prior history of neurological or psychiatric disease.

RESULTS

Clusters of immunoreactive cell bodies and high densities of neurokinin-immunoreactive fibers were located in the periaqueductal gray, the dorsal motor nucleus of the vagus and in the reticular formation of the medulla, pons and mesencephalon. Moreover, immunoreactive cell bodies were found in the inferior colliculus, the raphe obscurus, the nucleus prepositus hypoglossi, and in the midline of the anterior medulla oblongata. In general, immunoreactive fibers containing neurokinin were observed throughout the whole brainstem. In addition to the nuclei mentioned above, the highest densities of such immunoreactive fibers were located in the spinal trigeminal nucleus, the lateral reticular nucleus, the nucleus of the solitary tract, the superior colliculus, the substantia nigra, the nucleus ambiguus, the gracile nucleus, the cuneate nucleus, the motor hypoglossal nucleus, the medial and superior vestibular nuclei, the nucleus prepositus hypoglossi and the interpeduncular nucleus.

CONCLUSION

The widespread distribution of immunoreactive structures containing neurokinin in the human brainstem indicates that neurokinin might be involved in several physiological mechanisms, acting as a neurotransmitter and/or neuromodulator.

Propranolol blocks the tachycardia induced by galanin (1-15) but not by galanin (1-29)

The efferent pathways involved in the tachycardia induced by intracisternal injections of the N-terminal galanin fragment (1-15) (GAL (1-15)) and galanin (GAL (1-29)) has been evaluated in rats pretreated with the cholinergic antagonist atropine or the beta-antagonist propranolol. The pretreatment with propranolol significantly blocked the tachycardic and vasopressor effect produced by intracisternal injection of GAL (1-15) (p<0.05), but the pretreatment with atropine did not modify these cardiovascular effects. However, the cardiovascular response elicited by GAL (1-29) is modified by the pretreatment with atropine (p<0.05) but not by propranolol. These findings demonstrate that the central cardiovascular action of GAL (1-15), but not GAL (1-29), is mediated by beta-receptor stimulation and this suggests the existence of a different pathway involved in the cardiovascular response produced by the N-terminal galanin fragment as compared with the parent molecule GAL (1-29).

[Implication of the neuropeptides methionine enkephalin, neurotensin and somatostatin of the caudal trigeminal nucleus in the experimental migraine]

INTRODUCTION

Primary peptidergic sensory neurons of the trigeminal ganglion that innervate the cerebral dura have been involved in the pathogenesis of headache, including the migraine. In addition, it is known that nociceptive central processes of the trigeminal neurons terminate in the caudal trigeminal nucleus. Moreover, the electrical stimulation of the trigeminal ganglion has been used as an experimental model in order to study the vascular headache, including the migraine.

AIM

To study whether there is or not a decrease of the immunoreactivity for methionine enkephalin, somatostatin and neurotensin in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion.

MATERIAL AND METHODS

The trigeminal ganglia of Wistar albino rats of both sexes were electrically stimulated (frequency, 5 Hz; duration, 5 ms; intensity, 0,8 1.4 mA) and unilaterally for five minutes. Sections of the medulla oblongata containing the caudal trigeminal nucleus were obtained and processed for immunocytochemistry, in which specific antibodies were used against methionine enkephalin, neurotensin and somatostatin 28.

RESULTS

In stimulated animals, we observed a decrease in the immunoreactivity for the three neuropeptides studied in the stimulated (ipsilateral) side, in comparison with the not stimulated side (contralateral). In control animals (not stimulated) the degree of the immunoreactivity was the same on both sides.

CONCLUSIONS

1. The decrease of the immunoreactivity in the ipsilateral side (stimulated) suggests that methionine enkephalin, neurotensin and somatostatin 28 are released in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion; 2. Methionine enkephalin and somatostatin 28 could act in the caudal trigeminal nucleus as inhibitors (with antinociceptive action) of another released exciters neuropeptides (with nociceptive action); and 3. These data will allow in the future to try new therapeutic strategies (e.g., the inhibition of the receptors implicated.), in order to alleviate certain headaches.

Distribution of alpha-neoendorphin immunoreactivity in the diencephalon and the brainstem of the dog

Alpha-neoendorphin (alpha-NE) is an opiate decapeptide derived from the prodynorphin protein. Its anatomical distribution in the brain of mammals other than the rat, particularly in carnivores, is less well known than for other opiate peptides. In the present work, we have charted the distribution of alpha-NE immunoreactive fibers and perikarya in the diencephalon and the brainstem of the dog. The highest densities of labeled fibers were found in the substantia nigra and in patches within the nucleus of the solitary tract. Moderate densities appeared in the arcuate nucleus (Ar), median eminence, entopeduncular nucleus, ventral tegmental area, retrorubral area, periaqueductal central gray, interpeduncular nucleus and lateral parabrachial nucleus. Groups of numerous labeled perikarya were localized in the magnocellular hypothalamic nuclei, Ar and in the central superior and incertus nuclei in the metencephalon. Moreover, less densely packed fibers and cells appeared widely distributed throughout many nuclei in the region studied. These results are discussed with regard to the pattern described in other species. In addition, the present results were compared with the distribution of met-enkephalin immunoreactivity in the diencephalon and the brainstem of the dog that we have recently described. Although the distributions of these two peptides overlap in many areas, the existence of numerous differences suggest that they form separate opiate systems in the dog.

Central galanin and N-terminal galanin fragment induce c-Fos immunoreactivity in the medulla oblongata of the anesthetized rat

This immunohistochemical study analyzed the c-Fos expression (c-Fos-ir) induced by galanin injections. Galanin and N-terminal galanin fragment (1-15) induced a significant increase of c-Fos expression (c-ir) within the medulla oblongata 90 min and 6 h. after intracisternal injections. This expression has been studied mainly in the nucleus of the solitary tract and in the ventrolateral medulla showing different temporal profiles for both peptides. The presence of c-Fos-ir in TH-positive cells was analyzed in all the groups. These results may be relevant to understand the role of galanin in several functions including central cardiovascular control.

[Neuropeptides in the raphe nuclei: an immunocytochemical study]

INTRODUCTION

The raphe nuclei are involved in numerous mechanisms, included the antinociceptives. In the raphe nuclei of the cat, the distribution of neuropeptides is not very studied. Aim. To know the distribution of peptidergic fibers and cell bodies in the raphe nuclei of the cat. We studied a total of fifteen neuropeptides.

MATERIAL AND METHODS

We used four control cats (without colchicine) and six with colchicine (administered into the Sylvian aqueduct). We used an indirect immunocytochemical technique. The histologic controls carried out confirm the specificity of the primary and secondary antibodies used.

RESULTS

We observed in the fibers and/or the cell bodies located in the dorsal raphe nucleus a total of 14 neuropeptides, 12 in the raphe pallidus, 11 in the medial raphe, 10 in the raphe magnus, 8 in the raphe pontis and 7 in the raphe obscurus. We observed immunoreactive cell bodies in the raphe pallidus (with neurokinin A/leucine enkephalin), in the medial raphe (beta endorphin/alpha neo endorphin), in the raphe magnus (leucine enkephalin) and in the dorsal raphe (beta endorphin/alpha neo endorphin/methionine enkephalin Arg6 Gly7 Leu8/leucine enkephalin/neurokinin A/neurotensin).

CONCLUSIONS

1. There are differences on the distribution of the peptidergic fibers/cell bodies observed in the raphe nuclei of the rat, the cat and the man; 2. The raphe nuclei could receive peptidergic afferences containing dynorphin A, galanin, neuropeptide Y, somatostatin ; 3. The cell bodies located in the medial raphe and containing beta endorphin or alpha neo endorphin could be projecting neurons; 4. There is a great functional complexity in the raphe nuclei due to the great number of neuropeptides observed in them; 5. The neuropeptides could interact between them, and 6. The neuropeptides located in the raphe nuclei could be involved in the control of the nociceptive information.

Depletion of substance P, neurokinin A and calcitonin gene-related peptide from the contralateral and ipsilateral caudal trigeminal nucleus following unilateral electrical stimulation of the trigeminal ganglion; a possible neurophysiological and neuroanatomical link to generalized head pain

Primary trigeminal neurons of the trigeminal ganglion (TG) innervate major parts of the face and head, including the dura. Electrical stimulation of the TG at specific parameters, can activate its nociceptive neurons and may serve as an experimental pain model. Markowitz [J. Neurosci. 7 (1987) 4129] reported that electrical stimulation of the trigeminal ganglion (TG) causes extravasation of plasma proteins from venules of the trigeminally innervated domain possibly due to the release of vasoactive substances. Neurogenic inflammation (vasodilatation, plasma protein extravasation, release of vasoactive peptides) in dura may serve as one of the possible pathomechanisms underlying vascular head pain [Moskowitz, Ann. Neurol. 16 (1984) 157]. We performed a unilateral electrical stimulation (7.5 Hz, 5 ms, 0.8-1.4 mA for 5 min) of the TG in rat, to induce a neurogenic inflammation in the peripheral trigeminal domain including the dura, looking for calcitonin gene related peptide (CGRP), substance P (SP) and neurokinin A (NKA) immunoreactivity (IR) in the caudal trigeminal nucleus (CTN) into which massive central trigeminal processes terminate. Here, we show patchy depletion(s) of CGRP-, SP- and NKA-IRs in the contralateral CTN of the rat in addition to their ipsilateral depletion. Such depletion is due to the release of these neuropeptides in the CTN leading to the activation of bilateral trigeminal nociceptive pathway. These data afford the possibility that under specific frequencies (which may roughly correlate to the intensity of the painful stimulus) and/or specific intensities (may correlate to specific areas of the peripheral trigeminal domain) of stimulation, activation of one side of the TG may activate bilateral trigeminal nociceptive pathway leading to the perception of an ill localized/generalized pain or headache rather than a unilateral one.

Distribution of somatostatin-28 (1-12) immunoreactivity in the diencephalon and the brainstem of the dog

The term somatostatin refers to a family of peptides, mainly somatostatin-14, somatostatin-28 and somatostatin-28 (1-12), which are the cleavage products of a single 116 amino acid-long preprosomatostain molecule. The production of antibodies to these peptides allows their localization in a number of neuronal populations throughout the entire neuroaxis in many mammals. The dog has been pointed out as an extremely useful animal model for studying age-related cognitive dysfunction and other neuronal changes associated with aging in which somatostatin appears to be involved. However, only very scanty information is available with regard to the distribution of somatostatin in the brain of the dog. In the present work we have determined the pattern of the distribution of somatostatin-28 (1-12) immunoreactivity in the diencephalon and the brainstem of the dog. High to moderate densities of labeled perikarya were found in the anterior periventricular and arcuate hypothalamic nuclei, the reticular thalamic nucleus, in delimited parts of the nucleus of the brachium inferior colliculus, the retrorubral area, the dorsal raphe nucleus, the myelencephalic reticular formation and the dorsal motor nucleus of the vagus. Less dense population of somatostatin cells were localized in other diencephalic and brainstem nuclei. The distribution of labeled fibers was even broader as in addition to those above mentioned there were a number of areas that appeared devoid of labeled perikarya. Many of the findings were similar to those reported in earlier works while others underlined the existence of inconsistencies in the distribution pattern of this peptide in the brain of mammals.

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.

The galanin receptor antagonist M40 blocks the central cardiovascular actions of the galanin N-terminal fragment (1-15)

It has been shown that galanin plays a role in central cardiovascular regulation. Galanin administered centrally induces an increase of heart rate and a weak vasodepressor response, whereas the N-terminal galanin fragment (1-15) elicits vasopressor effects and tachycardia. Furthermore, it has been shown that galanin-(1-15), but not galanin-(1-29), decreases the baroreceptor reflex sensitivity. Since these data demonstrate that both galanin and its N-terminal fragment (1-15) exert a different modulation on central cardiovascular control, the aim of this work has been to study if the specific galanin receptor antagonist Galanin-(1-12)-Pro-(Ala-Leu)(2)-Ala]-amide (M40) could modulate their cardiovascular actions. Urethane anaesthetized rats were injected intracisternally and the changes in mean arterial pressure and heart rate were monitored. Two doses of M40 alone have been tested for their cardiovascular effects. With the dose of 1.0 nmol, a significant tachycardia was observed (P<0.001), but 0.1 nmol was ineffective. This suggests a possible agonistic effect for the higher doses of M40. The galanin receptor antagonist M40 at the dose of 0.1 nmol failed to modify the weak vasodepressor effects and tachycardia induced by 3.0 nmol of galanin-(1-29). However, the same dose completely blocked the vasopressor and tachycardic responses elicited by 3.0 nmol of galanin-(1-15). These data show that M40 differentially counteracts the central cardiovascular responses of the galanin fragment and give a functional support for the existence of galanin receptor subtypes within the brainstem. Therefore, the present findings can be explained on the basis that the cardiovascular actions of galanin-(1-29) could be mediated by one type of galanin receptor, whereas a galanin receptor subtype that recognizes N-terminal fragments of galanin may mediate the actions of galanin-(1-15).

Mapping of alpha-melanocyte-stimulating hormone-like immunoreactivity in the cat brainstem

The distribution of alpha-melanocyte-stimulating hormone-like immunoreactive structures was studied in the brainstem of the cat using an indirect immunoperoxidase technique. Immunoreactivity was observed in several brainstem nuclei of the cat in which no immunoreactivity had been previously reported. Immunoreactive fibres were observed in the following; the inferior central nucleus; the pontine gray nuclei; the Kölliker-Fuse nucleus; the motor trigeminal nucleus, the anteroventral cochlear nucleus; the abducens nucleus; the retrofacial nucleus; the superior, lateral, inferior, and medial vestibular nuclei; the lateral nucleus of the superior olive; the external cuneate nucleus; the nucleus of the trapezoid body; the postpyramidal nucleus of the raphe; the medial accessory inferior olive; the dorsal accessory nucleus of the inferior olive; the nucleus ambiguus; the principal nucleus of the inferior olive; the preolivary nucleus; the nucleus ruber; the substantia nigra; and in the area postrema. Our results point to a more widespread distribution of alpha-melanocyte-stimulating hormone-like immunoreactive structures in the cat brainstem than that reported in previous studies carried out in the same region of the cat, rat and humans.

Distribution of luteinizing hormone-releasing hormone in the upper brainstem and diencephalon of the cat: an immunocytochemical study

The distribution of luteinizing hormone-releasing hormone (LH-RH)-immunostained cell bodies and fibres was studied in the brainstem and diencephalon of the cat using an indirect immunoperoxidase technique. The brainstem and the thalamus were devoid of immunostained cell bodies, whereas in the hypothalamus immunopositive perikarya were observed in the supraoptic nucleus, the anterior hypothalamus, the preoptic region and in the arcuate nucleus. Our findings also showed that the hypothalamus is richer in immunostained fibres, and that in this region such fibres are more widely distributed than in the thalamus and upper brainstem. No immunopositive fibres were observed in the lower brainstem. Our results point to a more widespread distribution of LH-RH-immunostained perikarya in the cat hypothalamus than that previously reported in the cat; a similar distribution to that found in the rat, and a more restricted distribution than in primates. Additionally, our study shows a more widespread distribution of immunostained fibres in the cat brainstem and diencephalon than that previously described for other mammals. In this context, our results describe for the first time in the mammals central nervous system fibres containing LH-RH located in the stria medullaris of the thalamus, the supramammillary decussation, the laterodorsal and lateroposterior thalamic nuclei, the nucleus reuniens, the supraoptic nucleus, and the optic chiasm. Thus, our findings reveal that LH-RH-immunostained structures are widely distributed in the upper brainstem and in the diencephalon of the cat, suggesting that the peptide may be involved in several physiological functions.

Simultaneous depletion of neurokinin A, substance P and calcitonin gene-related peptide from the caudal trigeminal nucleus of the rat during electrical stimulation of the trigeminal ganglion

The central terminals of the primary sensory trigeminal ganglion (TG) neurons projecting into the caudal trigeminal nucleus (CTN) of the rat exhibit neurokinin A (NKA)-, substance P (SP)-, and calcitonin gene-related peptide (CGRP)-immunoreactivities (IRs). We stimulated the TG in the rat to induce some of the alterations which might occur during migraine (neurogenic inflammation). Under a stereotaxic apparatus and by means of a bipolar electrode, one-side TG of the animals were electrically stimulated (7.5 Hz, 5 ms, 0.8-1. 4 mA) with square pulses for 5 min. Then, using immunohistochemical methods, the lower medulla of each rat was studied for NKA-, SP- and CGRP-IRs. Light microscopic examination of brain-stem sequencial sections revealed a simultaneous decrease in the immunoreactivities of all neuropeptides (NKA, SP and CGRP) in the CTN ipsilateral to TG stimulation in comparison with the other (not stimulated) side CTN. It is suggested that this decrease in immunoreactivity would be due to the co-release of neuropeptides following noxious stimuli and that NKA, SP and CGRP might therefore act as co-transmitters or co-modulators at the first central synapses of the trigeminal sensory pathway.

Alterations in neurokinin A-, substance P- and calcitonin gene-related peptide immunoreactivities in the caudal trigeminal nucleus of the rat following electrical stimulation of the trigeminal ganglion

We have carried out an immunohistochemical study on the presence of neurokinin A (NKA) and substance P (SP) in the rat caudal trigeminal nucleus (CTN) after electrical stimulation of the trigeminal ganglion (TG), used as an experimental model to induce alterations, some of which may occur during migraine attacks (release of vasoactive peptides from perivascular trigeminal axons and neurogenic inflammation). Both unilateral, 30 min electrical stimulation (5 Hz, 5 ms, 0.1-1 mA) of the TG and 5 min stimulation with a slight increase in the stimulating parameters (7.5 Hz, 5 ms, 1.4 mA) caused a significant depletion of the NKA and SP immunoreactivities (-IR) of the TG nerve central terminals in the ipsilateral CTN. Calcitonin gene-related peptide (CGRP)-IR of the ipsilateral CTN was also studied in the CTN using the increased stimulating parameters and a marked depletion of CGRP-IR was also observed following TG stimulation. Such depletion may be due to the release of neuropeptides from the trigeminal central terminals. These findings suggest that NKA, SP and CGRP could act as neurotransmitters at the first central synapses of the trigeminal nociceptive pathway to transmit the sensory stimuli to the higher brain centers.

Anatomical distribution of beta-endorphin (1-27) in the cat brainstem: an immunocytochemical study

Using an indirect immunoperoxidase technique, we studied the location of beta-endorphin (1-27) fibres and cell bodies in the cat brainstem. The highest density of immunoreactive fibres was found in the lateral and medial parabrachial nuclei and in the locus coeruleus; a moderate density was observed in the periaqueductal gray and the central reticular nucleus, and a low density was observed in the interpeduncular nucleus, the nucleus incertus, the raphe pallidus nucleus, the paralemniscal reticular nucleus, the laterodorsal tegmental nucleus, the pericentral division of the dorsal tegmental nucleus and the lateral reticular nucleus. Immunoreactive neurons were observed in the superior central nucleus, the pericentral division of the dorsal tegmental nucleus, the interpeduncular nucleus, the nucleus incertus and the dorsal raphe nucleus. Our results point to a more widespread distribution of beta-endorphin (1-27)-immunoreactive perikarya in the cat brainstem in comparison with previous studies carried out in the same region of other mammals. The distribution of beta-endorphin (1-27)-immunoreactive fibres and perikarya is compared with the location of other neuropeptides in the cat brainstem. Moreover, our findings reveal that beta-endorphin (1-27)-immunoreactive structures are widely distributed in the cat brainstem, suggesting that the peptide might be involved in several physiological functions.

Immunohistochemical mapping of enkephalins, NPY, CGRP, and GRP in the cat amygdala

This immunohistochemical study shows a wide distribution of neuropeptides in the cat amygdala. Neuropeptide Y is present along the whole amygdaloid complex, and fibers and cell bodies containing neuropeptide Y are observed in all the nuclei studied. Leucine-enkephalin-, gastrin-releasing peptide/bombesin-, and calcitonin gene-related peptide-immunoreactive fibers and perikarya are observed only in discrete nuclei of the amygdaloid complex, whereas only fibers -but no cell bodies- containing methionine-enkephalin-Arg6-Gly7-Leu8 have been observed. No immunoreactivity has been found for gamma-melanocyte-stimulating hormone, dynorphin A (1-17), or galanin. These data are compared with those reported in the amygdala of other mammals.