Distribution of histaminergic neurons in the brain of the lamprey Lampetra fluviatilis as revealed by histamine-immunohistochemistry

An antiserum against conjugated histamine was used to study the distribution of histaminergic neurons in the CNS of the lamprey Lampetra fluviatilis. Numerous histamine-immunoreactive cell bodies were detected in the dorsal and ventral hypothalamic nuclei and in the adjacent postinfundibular commissural nucleus. Histamine-immunoreactive fibers of high density were present in the ventral hypothalamus, and fibers could also be traced dorsally from the hypothalamus to the corpus striatum and septal nucleus where they appeared to terminate in dense plexuses. Another, smaller group of histamine-immunoreactive perikarya was observed in the border area between mesencephalon and rhombencephalon, near the caudal pole of the mesencephalic reticular nucleus. Sparsely distributed histamine-immunoreactive fibers were present in the ventral mesencephalon. The distribution of histaminergic neurons in cyclostomes, which diverged very early from the main vertebrate line, shows similarities with the corresponding systems in the CNS of amphibians and mammals, which suggests that histaminergic neuronal systems are phylogenetically old and have been conserved during evolution.     

Development of histamine-immunoreactive neurons in the rat brain

This study was undertaken to reveal the cellular stores of histamine in developing rat brain and to determine the stage of development during which the histamine-immunoreactive neurons can first be detected. Rats from embryonal day 12 to postnatal day 14 were studied. The brains were fixed in 4% 1-ethyl-3(3-dimethylaminopropyl)carbodiimide and standard immunofluorescence technique was used. The first histamine-immunoreactive neurons were seen on embryonic day 13 in the border of mesencephalon and metencephalon. On embryonic day 15 immunoreactive neurons were detected in ventral mesencephalon and rhombencephalon. In caudal, tuberal, and postmammillary caudal magnocellular nuclei histamine-immunoreactive neurons were first detected on embryonic day 20 while those in the hindbrain had disappeared. Histamine-immunoreactive nerve fibers were first detected on embryonic day 15 in rhombencephalon and mesencephalon and in some areas of diencephalon including the mammillary bodies and frontal cortex. On embryonic day 18 the number of immunoreactive nerve fibers in the hindbrain had decreased considerably, but the olfactory bulb, septal and hypothalamic area, and the cerebral cortex showed immunoreaction in fibers. The density of histamine-immunoreactive fiber networks increased until postnatal day 14 when an adultlike pattern of neurons and fibers had developed. Histamine-immunoreactive neurons are present in embryonal CNS and they develop extensive projections to various brain areas.     

Fine structure of histaminergic neurons in the caudal magnocellular nucleus of the rat as demonstrated by immunocytochemistry using histidine decarboxylase as a marker

The morphology of histamine-containing neurons in the caudal magnocellular nucleus was light and electron microscopically examined by means of peroxidase-antiperoxidase (PAP) immunocytochemistry with histidine decarboxylase (HDC) as a marker. HDC-like immunoreactive (HDCI) neurons had large (25–30 μm in diameter) perikarya from which two to four primary dendrites arose. The perikarya had a nearly round nucleus and well-developed Golgi apparatus in addition to a large number of mitochondria and rough endoplasmic reticulum. Immunoreactive endproducts were found diffusely throughout the perikarya, dendrites, and axons. HDCI neurons made synaptic contact with nonreactive axon termminals on the perikarya and dendrites. In addition, the HDCI neurons very frequently formed puncta adherentia with neuronal elements, either HDCI or nonreactive, or glial cells. Most of the HDCI axon terminals serially observed under electron microscopy did not exhibit typical synaptic contact in the caudal magnocellular nucleus. These findings suggest the nonsynaptic release of histamine in the caudal magnocellular nucleus.     

N-acetylaspartylglutamate immunoreactivity in neurons of the monkey's visual pathway.

The acidic dipeptide N-acetylaspartylglutamate (NAAG) was identified immunohistochemically within neurons of the visual pathways of two adult macaque monkeys which had undergone midsagittal sectioning of the optic chiasm 6 or 9 years earlier. In both temporal and nasal retinae, amacrine cells, including some displaced amacrine cells, expressed NAAG immunoreactivity. In temporal but not nasal retina, retinal ganglion cells were stained, as were their dendrites in the inner plexiform layer, and their axons in the optic nerve fiber layer. In nasal retina, the ganglion cells had degenerated because they were axotomized by the optic chiasm section. In the target regions of the retinal ganglion cells, the superior colliculus and the lateral geniculate nucleus (LGN), both neuropil and cell bodies were stained. In LGN, staining was confined to layers 2, 3, and 5, that is, to the layers innervated by the intact ipsilateral pathway. Immunoreactivity was also seen in the cells of layers 2, 3A, 4B, 5, and 6 of area 17 and layers 3 and 5 of area 18. The neuropil was stained in all layers of area 17, but more heavily in layers 1, 2, 4B, the bottom of 4C beta, 5B, and 6B. Within 4C the staining was patchy; in tangential sections there were alternating bands of light and dark label which matched the ocular dominance bands demonstrated by cytochrome oxidase histochemistry in adjacent sections. This banding pattern is consistent with the presence of NAAG in geniculocortical terminals of the intact ipsilateral pathway and the absence of such terminals for the contralateral pathway, which had undergone transneuronal degeneration due to the optic chiasm sectioning. Overall, our results for monkey are very similar to those in cat and suggest that NAAG or a structurally related molecule may have a prominent role in the communication of visual signals at retinal, thalamic, and cortical levels.     

Role of histaminergic neurons in hypnotic modulation of brain processing of visceral perception

Modulating visceral sensation of the body is important to the understanding of emotion formation. Molecules that act during hypnosis and modify visceral pain perception are not known. We tested our hypothesis that hypnotic suggestion changes electrophysiological processing of visceroafferent signals in the human brain and that these conditions are in part dependent on histaminergic neurons. Twelve healthy male subjects were studied on two separate days: a day of treatment with histamine H1 receptor antagonist (d-chlorpheniramine 100 microg kg(-1), intravenously) and another day of that with placebo (saline, the same amount) in a randomized order. We recorded cortical evoked potentials to 100 rectal electrical stimuli after neutral, hyperalgesic or analgesic hypnotic suggestions as given to modulate the visceral perception. Analgesic suggestion reduced the amplitude of the deepest positive peak of viscerosensory evoked potential. Administration of histamine H1 antagonist diminished the attenuation of viscerosensory evoked potential by analgesic suggestion. Our results suggest that central pain modulatory system in the brain is activated by hypnotic suggestion and that brain histamine is a mediator in the hypnotic modulation of visceral sensory pathway as well as in the control of consciousness level. These findings lead us to possible new treatment for control of visceral perception.     

Histaminergic system in the tree shrew brain

This study mapped the histamine-immunoreactive neuronal system in the brain of the tree shrew (Tupaia belangeri) and compared its structure with that of the rat and guinea pig. The histamine-containing cell bodies lay in the posterior ventral hypothalamus in the tuberomammillary complex, as in the rodents. The morphology of this complex resembled that of the rat. The histaminergic axons projected to nearly all parts of the brain. The main ascending bundle ran ventromedially: the densest innervation was found in the ventral hypothalamus, preoptic area, septum, medial part of nucleus accumbens, and bed nucleus of the stria terminalis. High fiber densities were present in the amygdaloid nuclei and claustrum. Another pathway ran dorsomedially along the periventricular hypothalamus and sent fibers to all parts of the diencephalon. Part of these fibers followed the central gray to the midbrain and spread laterally below the inferior colliculus. Another descending pathway ran through the interfascicular and medial raphe nuclei to meet the pontine central gray. The densest fiber networks were seen in the dorsal tegmental and parabrachial nuclei, and around the locus coeruleus. Also the substantia nigra, interpeduncular and mesencephalic reticular nuclei, colliculi, and vestibular and raphe nuclei received a dense histaminergic innervation. The organization of the fibers in the tree shrew brain resembled more that in the guinea pig than that in the rat. As compared with the guinea pig, more fibers were present, particularly in the globus pallidus, central thalamus, and deep cerebellar nuclei. No fibers were seen in the outer layer of the piriform cortex. In Tupaia, a laminar organization of the fibers was evident in the hippocampus, in contrast to the rodents. Also, a dense periventricular fiber plexus was prominent.     

中枢组胺能系统研究的新进展

近年来对于中枢组胺能系统的研究 ,在组胺受体的分子生物学、组胺能系统的生理功能 ,以及组胺能神经传递功能的紊乱与某些脑疾病之间的关系等问题上取得了较大进展 ,本文对这些进展作一简要的综述。     

The histaminergic system in human thalamus: correlation of innervation to receptor expression

The mRNA expression of three histamine receptors (H1, H2 and H3) and H1 and H3 receptor binding were mapped and quantified in normal human thalamus by in situ hybridization and receptor binding autoradiography, respectively. Immunohistochemistry was applied to study the distribution of histaminergic fibres and terminals in the normal human thalamus. mRNAs for all three histamine receptors were detected mainly in the dorsal thalamus, but the expression intensities were different. Briefly, H1 and H3 receptor mRNAs were relatively enriched in the anterior, medial, and part of the lateral nuclei regions; whereas the expression level was much lower in the ventral and posterior parts of the thalamus, and the reticular nucleus. H2 receptor mRNA displayed in general very low expression intensity with slightly higher expression level in the anterior and lateropolar regions. H1 receptor binding was mainly detected in the mediodorsal, ventroposterolateral nuclei, and the pulvinar. H3 receptor binding was detected mainly in the dorsal thalamus, predominantly the periventricular, mediodorsal, and posterior regions. Very high or high histaminergic fibre densities were observed in the midline nuclear region and other nuclei next to the third ventricle, ventroposterior lateral nucleus and medial geniculate nucleus. In most of the core structures of the thalamus, the fibre density was very low or absent. The results suggest that histamine in human brain regulates tactile and proprioceptory thalamocortical functions through multiple receptors. Also, other, e.g. visual areas and those not making cortical connections expressed histamine receptors and contained histaminergic nerve fibres.     

Histamine-activated adenylate cyclase in brain homogenates of several species

Histamine has been shown to activate cyclic AMP synthesis in brain slices and homogenates of certain species, although less is known about species differences in brain homogenates. Dutch Belted and New Zealand White rabbit brain homogenates contained a histamine-responsive adenylate cyclase similar to that of the guinea pig. In contrast, adenylate cyclase of gerbil and hamster brain exhibited little or no stimulation by histamine. Male rat hypothalamic homogenates contained adenylate cyclase, but also exhibited minimal stimulation by histamine, in disagreement with some recent reports. Detailed studies of the conditions of assay failed to resolve this discrepancy.     

Subicular efferents to histaminergic neurons in the posterior hypothalamic region of the rat studied with PHA-L tracing combined with histidine decarboxylase immunocytochemistry.

The projections from the subiculum to histaminergic cells in the posterior hypothalamic region of the rat were studied by means of anterograde neuroanatomical tracing with Phaseolus vulgaris-leucoagglutinin (PHA-L) combined with histidine decarboxylase (HDC)-immunohistochemistry. PHA-L was injected at various loci along the dorsoventral and proximodistal axes of the subiculum. This resulted in labeling of the fornix and of terminal plexuses at various locations in the diencephalon and the mammillary body. Following deposition of PHA-L in the proximal part of the dorsal subiculum, labeled fibers in the posterior hypothalamus were confined to the mammillary nuclei, whereas after injections of PHA-L in the distal part of the dorsal subiculum and the entire ventral subiculum, labeled fibers were also present in clusters of histaminergic cells located around the mammillary nuclei. The density of the PHA-L labeled fibers within these clusters increased from low to moderate in association with a shift of the injection sites from dorsal to ventral and from proximal to distal parts of the subiculum, i.e., the highest fiber labeling was seen after injections of PHA-L in the distal part of the ventral subiculum. In the latter experiments, PHA-L labeled fibers reached HDC-immunoreactive neurons in the tuberal magnocellular nucleus, the deepest layer of the caudal magnocellular nucleus, the two bridges of histaminergic cells in the posterior hypothalamus, and the histaminergic neurons scattered in the supramammillary region. A few labeled fibers invaded the postmammillary caudal magnocellular nucleus. The presence of varicosities on the PHA-L labeled fibers in close proximity to the cell bodies and dendrites of the histaminergic neurons suggest the existence of synaptic contacts.     

Antagonism of vasoactive intestinal peptide mRNA in the suprachiasmatic nucleus disrupts the rhythm of FRAs expression in neuroendocrine dopaminergic neurons

This study was designed to determine whether there is a functional relationship between cfos expression in vasoactive intestinal peptide (VIP) -containing neurons of the suprachiasmatic nucleus (SCN) and Fos-related antigens (FRAs) expression in neuroendocrine dopaminergic neurons of the arcuate (ARN) and periventricular (PeVN) nuclei of the hypothalamus. Brains were obtained from ovariectomized (OVX) female rats killed at 12:00 AM, 7:00 AM, 9:00 AM, 12:00 PM, and 7:00 PM (12 hours illumination beginning 6:00 AM). Antibodies against FRAs and tyrosine hydroxylase (TH) identified activated neuroendocrine dopaminergic neurons. Antibodies against cfos and VIP identified activated VIP-immunoreactive (IR) neurons in the SCN. The proportion of neuroendocrine dopaminergic neurons in the ARN and PeVN expressing FRAs was greatest and equivalent at 7:00 AM, 9:00 AM, 12:00 PM, and 12:00 AM. At 7:00 PM, the proportion of neuroendocrine dopaminergic neurons expressing FRAs was significantly lower than all other time points. In the SCN, a subpopulation of VIP-IR neurons maximally expressed cfos at 7:00 AM, which decreased through 9:00 AM. cFos was not expressed at 7:00 PM and 12:00 AM in VIP-IR neurons. Antisense VIP oligonucleotides were injected into the SCN to determine whether attenuation of VIP expression disturbs rhythms in neuroendocrine dopaminergic neuronal activity. OVX rats were infused with either antisense VIP oligonucleotides or scrambled sequence oligonucleotides bilaterally (0.5 microg in 0.5 microl of saline per side) in the SCN. Animals were killed 34 hours (7:00 PM) and 46 hours (7:00 AM) after receiving infusions, and brains were recovered. Administration of antisense VIP oligonucleotides decreased VIP protein expression in the SCN and prevented the decrease in the percentage of neuroendocrine dopaminergic neurons expressing FRAs at 7:00 PM but did not affect FRAs expression at 7:00 AM when compared with animals receiving scrambled oligonucleotides. These data suggest that VIP fibers from the SCN may relay time-of-day information to neuroendocrine dopaminergic neurons to inhibit their activity and, thus, initiate prolactin release in the evening.     

Innervation of histaminergic neurons in the posterior hypothalamic region by medial preoptic neurons. Anterograde tracing with Phaseolus vulgaris leucoagglutinin combined with immunocytochemistry of histidine decarboxylase in the rat

By means of anterograde neuroanatomical tracing with Phaseolus vulgaris leucoagglutinin (PHA-L) combined with immunohistochemistry of histidine decarboxylase (HDC), we studied in the rat whether the histaminergic neurons in the posterior hypothalamic region are innervated by fibers arising from neurons in the medial preoptic region (MPO). We injected the tracer at various locations in the MPO. Following survival, frozen brain sections were dual-stained according to a protocol using PHA-L and HDC immunocytochemistry. From all parts of the MPO, PHA-L-labeled fibers course to ipsi- and contralateral clusters of histaminergic neurons located in the posterior hypothalamus. Varicosities on the PHA-L-labeled fibers can be observed in close association with HDC-immunoreactive cell bodies and dendrites in all the histaminergic cell clusters in the posterior hypothalamus. These associations suggest synaptic connectivity.     

Coexistence of adenosine deaminase, histidine decarboxylase, and glutamate decarboxylase in hypothalamic neurons of the rat

Neurons immunoreactive for the enzyme adenosine deaminase (ADA) in the posterior basal hypothalamus of the rat have a distribution pattern similar to those immunoreactive for histidine decarboxylase (HDC) and are particularly numerous in the tuberal (TM), caudal (CM) and postmammillary caudal (PCM) hypothalamic magnocellular nuclei which harbor neurons containing glutamic acid decarboxylase (GAD). The extent to which these enzymes coexist within neurons of these hypothalamic regions was examined using either serial sections or simultaneous immunostaining for ADA and HDC or GAD in the same section. Analysis of serial sections revealed neuronal coexistence of ADA with HDC or GAD in both TM and CM. In addition some neurons in CM, the only area examined for triple coexistence, were found to contain all three enzymes. In sections processed for ADA simultaneously with HDC or GAD, nearly all ADA-immunoreactive neurons in TM, CM, and PCM as well as those scattered between these nuclei were found to contain HDC, and nearly all contained GAD. Exceptions to this, however, were small cells located lateral to the posterior arcuate nucleus, which appeared to contain ADA but not HDC, and large neurons located at the anterior extreme of TM, which appeared to contain ADA but not GAD. The relatively few ADA- compared with GAD-containing neural systems in brain, together with the presence of ADA in GAD-containing hypothalamic magnocellular neurons, which appear to have widespread projections throughout the brain, indicate that ADA may be a convenient immunohistochemical marker for anatomical investigations of these projections.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of cholinergic and GABAergic neurons in the rat medial septum: Different onset of choline acetyltransferase and glutamate decarboxylase mRNA expression

In the present study, we have investigated the developmental expression of the transmitter-synthesizing enzymes choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) in rat medial septal neurons by using in situ hybridization histochemistry. In addition, we have employed immunostaining for ChAT and the calcium-binding protein parvalbumin, known to be contained in septohippocampal GABAergic neurons. A large number of GAD67 mRNA-expressing neurons were already observed in the septal complex on embryonic day (E) 17, the earliest time point studied. During later developmental stages, there was mainly an increase in the intensity of labeling. Neurons expressing ChAT mRNA were first recognized at E 20, and their number slowly increased during postnatal development of the septal region. The adult pattern of ChAT mRNA-expressing neurons was observed around postnatal day (P) 16. By using a monoclonal ChAT antibody, the first immunoreactive cells were not seen before P 8. Similarly, the first weakly parvalbumin-immunoreactive neurons were seen in the septal complex by the end of the 1st postnatal week. These results indicate that in situ hybridization histochemistry may be an adequate method to monitor the different development of transmitter biosynthesis in cholinergic and GABAergic septal neurons. Moreover, the late onset of ChAT mRNA expression would be compatible with a role of target-derived factors for the differentiation of the cholinergic phenotype. © 1996 John Wiley-Liss, Inc.     

FKBP12 mRNA expression is upregulated by intrinsic CNS neurons regenerating axons into peripheral nerve grafts in the brain

We have examined the expression of the immunophilin FKBP12 in adult rat intrinsic CNS neurons stimulated to regenerate axons by the implantation of segments of autologous tibial nerve into the thalamus or cerebellum. After survival times of 3 days to 6 weeks, the brains were fresh-frozen. In some animals the regenerating neurons were retrogradely labelled with cholera toxin subunit B 1 day before they were killed. Sections through the thalamus or cerebellum were used for in situ hybridization with digoxygenin-labelled riboprobes for FKBP12 or immunohistochemistry to detect cholera toxin subunit B-labelled neurons. FKBP12 was constitutively expressed by many neurons, and was very strongly expressed in the hippocampus and by Purkinje cells. Regenerating neurons were found in the thalamic reticular nucleus and deep cerebellar nuclei of animals that received living grafts. Neurons in these nuclei upregulated FKBP12 mRNA; such neurons were most numerous at 3 days post grafting but were most strongly labelled at 2 weeks post grafting. Regenerating neurons identified by retrograde labelling were found to have upregulated FKBP12 mRNA. No upregulation was seen in neurons in animals that received freeze-killed grafts, which do not support axonal regeneration. We conclude that FKBP12 is a regeneration-associated gene in intrinsic CNS neurons.     

The effect of adrenalectomy on stress-induced c-fos mRNA expression in the rat brain

Previously, we determined the pattern of stress-induced c-fos mRNA expression throughout the brain in order to gain further insight into the identification of the neural circuits mediating stress-induced regulation of the hypothalamic-pituitary-adrenal axis. In the present study, we determined if rapid effects of increased glucocorticoid levels after stress contribute to changes in c-fos mRNA expression. To this end, stress-induced c-fos expression was characterized in adrenalectomized (ADX) or adrenalectomized and corticosterone replaced (ADX/B) male rats. Animals were sacrificed 30 min post-onset of a 10 min swim stress, and in situ hybridization histochemistry was used to detect c-fos mRNA throughout the brain. The pattern of c-fos induction in the ADX and ADX/B animals was similar to that observed in the sham operated animals. Additionally, densitometric measurements were made to quantify the c-fos response in the paraventricular nucleus of the hypothalamus and the CA1/2 region of the hippocampus. We found that ADX did not alter the magnitude of the c-fos response to stress in these areas, but there was a slight dampening of the response in ADX/B animals. In sum, these results suggest that the pattern of c-fos expression observed 30 min post-stress is independent of stress-induced increases in circulating glucocorticoid concentrations.     

Aromatic l-amino acid decarboxylase in the rat brain: coexistence with vasopressin in small neurons of the suprachiasmatic nucleus

We demonstrated the coexistence of aromatic L-amino acid decarboxylase (AADC) and arginine-vasopressin in neurons of the hypothalamic suprachiasmatic nucleus of Sprague-Dawley rats. Neurons that lacked monoamines but expressed immunoreactivity to the enzyme AADC occupied the rostral and caudal poles of the suprachiasmatic nucleus and mediodorsal and dorsolateral positions along the entire extent of the nucleus. AADC was also localized in similar neurons of the suprachiasmatic nucleus of rats from other strains including the homozygous Brattleboro rat.     

Differential expression of voltage-gated K+ and Ca2+ currents in bipolar cells in the zebrafish retinal slice

Whole-cell voltage-gated currents were recorded from bipolar cells in the zebrafish retinal slice. Two physiological populations of bipolar cells were identified. In the first, depolarizing voltage steps elicited a rapidly activating A-current that reached peak amplitude ≤ 5 ms of step onset. I_A was antagonized by external tetraethylammonium or 4-aminopyridine, and by intracellular caesium. The second population expressed a delayed rectifying potassium current (I_K) that reached peak amplitude ≥ 10 ms after step onset and did not inactivate. I_K was antagonized by internal caesium and external tetraethylammonium. Bipolar cells expressing I_K also expressed a time-dependent h-current at membrane potentials < – 50 mV. I_h was sensitive to external caesium and barium, and was also reduced by Na⁺-free Ringer. In both groups, a calcium current (I_Ca) and a calcium-dependent potassium current (I_K(Ca)) were identified. Depolarizing voltage steps > – 50 mV activated I_Ca, which reached peak amplitude between – 20 and – 10 mV. I_Ca was eliminated in Ca⁺²-free Ringer and blocked by cadmium and cobalt, but not tetrodotoxin. In most cells, I_Ca was transient, activating rapidly at – 50 mV. This current was antagonized by nickel. The remaining bipolar cells expressed a nifedipine-sensitive sustained current that activated between – 40 and – 30 mV, with both slower kinetics and smaller amplitude than transient I_Ca. I_K(Ca) was elicited by membrane depolarizations > – 20 mV. Bipolar cells in the zebrafish retinal slice preparation express an array of voltage-gated currents which contribute to non-linear I–V characteristics. The zebrafish retinal slice preparation is well-suited to patch clamp analyses of membrane mechanisms and provides a suitable model for studying genetic defects in visual system development.     

Sexual dimorphisms in the soma size of neurons in the brain of whiptail lizards (Cnemidophorus species)

Soma area was significantly larger in the anterior hypothalamus-preoptic area of male than female Cnemidophorus inornatus, and it was significantly larger in females than males in the ventromedial hypothalamus. These results parallel those on the volume of the brain areas in these animals, and therefore probably explain at least part of the dimorphisms seen in this sexually reproducing species. Soma size in parthenogenetic C. uniparens also parallels volume.