Fos and jun in rat central amygdaloid nucleus and paraventricular nucleus after stress.

The present paper describes the effect of capsaicin-induced stressful stimulus on the expression of immediate early genes (IEGs) c-fos, c-jun, junB and junD in the hypothalamic paraventricular nucleus (PVN) and the central amygdaloid nucleus (ACe) using in situ hybridization. Stress caused an intense expression of c-fos, c-jun and junB especially in the PVN and ACe and also a clear induction of junD was observed in the PVN. This suggests that the PVN and the ACe are two major targets of stress in the brain. The intense expression of the IEGs in the ACe and PVN suggests that stress may affect neurotransmitter gene expression through Fos and Jun proteins in both these nuclei.     

Projection from the ventrolateral medullary neurons containing tyrosine hydroxylase to the central amygdaloid nucleus in the rat.

By using a double-labeling produce of retrograde horseradish peroxidase (HRP) tracing and the immunocytochemical localization of tyrosine hydroxylase (TH), the present study ascertained that the axonal fibers of catecholaminergic neurons in the caudal ventrolateral medulla projected to the central amygdaloid nucleus in the rat. The majority of double-labeled cells were observed primarily around the level of the obex. 92% of HRP retrogradely labeled cells contained TH-like immunoreactive (TH-IR), but only 31% of TH-IR cells was labeled with HRP.     

Ventral mesencephalic neurons containing both cholecystokinin- and tyrosine hydroxylase-like immunoreactivities project to forebrain regions

The coexistence of cholecystokinin- and tyrosine hydroxylase-like immunoreactivities within neurons of the rat ventral mesencephalon was analyzed by using an indirect immunofluorescence technique for the simultaneous demonstration of two antigens in the same tissue section. A high degree of colocalization was observed in the substantia nigra pars compacta, in which 80-90% of all labeled neurons at rostral and up to 70% at intermediate levels contained both cholecystokinin and tyrosine hydroxylase. At caudal levels, the incidence of colocalization declined to approximately 30-50%. All of the immunoreactive perikarya in the substantia nigra pars lateralis were labeled with both substances. Other areas of the ventral midbrain that exhibited a moderate proportion of neurons immunoreactive for both cholecystokinin and tyrosine hydroxylase included the ventral tegmental area, interfascicular nucleus, and rostral and caudal linear nuclei. In addition, coexistence was occasionally observed within neurons of the central and ventral periaqueductal gray matter, supramammillary region, peripeduncular region, retrorubral field, and extremely rarely, within the substantia nigra pars reticulata. Cell bodies containing tyrosine hydroxylase-like immunoreactivity (indicative of dopamine) usually outnumbered those containing the peptide except in the supramammillary region and in the ventral periaqueductal gray matter, where the cholecystokinin perikarya were present in higher numbers. The double-labeling colocalization technique was combined with fluorescence retrograde tracing to determine some of the forebrain projections of these neurons. Ventral midbrain neurons containing both cholecystokinin and tyrosine hydroxylase were found to project to the caudate-putamen, nucleus-accumbens, prefrontal cortex, and amygdala. These projections originated from neurons located predominantly in the substantia nigra pars compacta and the ventral tegmental area. Thus, cholecystokinin occurs within the well-known dopaminergic nigrostriatal pathway in the rat. Overall, these results demonstrate that a significant proportion of the dopamine neurons giving rise to the ascending mesotelencephalic projections also contain the peptide cholecystokinin.     

Effects of neurotensin on neurons in the rat central amygdaloid nucleus in vitro

The effects of neurotensin (NT) on neurons in the central amygdaloid nucleus (ACe) were investigated in rat brain slice preparations by adding the peptide to the perfusing medium. Of 115 ACe neurons, 69 cells (60%) showed excitatory responses and 10 cells (9%) showed inhibitory responses to application of NT. The excitatory response to NT was observed in a dose-dependent manner and the threshold concentration was approximately 3 × 10⁻⁹ M. The excitatory effects of NT persisted under blockade of synaptic transmission. The NT fragment neurotensin 8–13 and the NT analogue neuromedin N showed effects similar to those of NT, whereas the NT fragment neurotensin 1–8 had no effect on ACe neurons. Of 43 neurons in the septal nucleus, 8 cells (19%) and 3 cells (7%) showed excitatory and inhibitory responses, respectively, to NT. The results suggest that NT exerts a potent excitatory effect on ACe neurons through a direct action on specific receptors, in which NT may play a role in amygdala-relevant functions.     

Role of the central amygdaloid nucleus in shaping the discharge of gustatory neurons in the rat parabrachial nucleus

The central amygdaloid nucleus (CeA) receives projection from the parabrachial nucleus (PBN) gustatory neurons and descendingly projects to the PBN. To assess if the CeA is involved in modulating the activity of gustatory neurons in the PBN, the effects of electrical stimulation and electrolytic lesion of CeA on PBN gustatory neurons were observed. Of 60 neurons observed, 30 were classified as NaCl-best, 18 as HCl-best, 5 as Quinine HCl (QHCl)-best, and 7 as sucrose-best. During CeA stimulation, the responses to at least one effective stimulus were inhibited in most PBN neurons, with the response magnitudes to HCl and QHCl significantly decreased (P<0.01). In contrast, bilateral lesions of CeA facilitated the responses to HCl and QHCl (P<0.01). According to the best-stimulus category, the effects on the responses to HCl and QHCl were similarly subjected to these modulations either during electrical stimulation or after electrolytic lesions of CeA. Analyses of across-unit patterns indicated that the CeA stimulation increased the chemical selection of PBN taste neurons while the CeA lesions depressed the effect on the chemical selection between NaCl and QHCl. These findings suggest that the CeA may be involved in mediating feeding behavior via modulating the activity of gustatory neurons of PBN.     

Electrophysiological characteristics of amygdaloid central nucleus neurons in the awake rabbit

Considerable evidence suggests that the amygdaloid central nucleus (ACE) may contribute importantly to autonomic regulation, possibly via direct ACE projections to the brainstem. Lacking, however, have been comprehensive data concerning the electrophysiological characteristics of ACE neurons. The present experiment was therefore undertaken in order to characterize the spontaneous activity and sensory-evoked responses of ACE neurons in the conscious rabbit. Particular attention was given to the identification, via antidromic activation, and characterization of those ACE neurons which project to the lower brainstem. Single-unit recordings were obtained from 100 histologically verified ACE neurons. Most of these, including all brainstem projection neurons, discharged at very low spontaneous rates and were unresponsive to the presentation of auditory, visual and somatic stimuli. Based upon spontaneous activity and sensory-evoked responses, the activity of other ACE neurons appeared to conform to one of several profiles. These included neurons showing increased activity to the presentation of all sensory stimuli, and neurons showing activity that was spontaneously entrained with the respiratory cycle. These data indicate the heterogeneous nature of ACE neuronal activity, and provide a basis for the comparison of additional experiments which concern the electrophysiological characteristics of the ACE.     

Morphology of peptide-containing neurons in the rat basolateral amygdaloid nucleus

The peroxidase-antiperoxidase (PAP) immunohistochemical technique was used to identify neurons in the basolateral amygdaloid nucleus (BL) that contain vasoactive intestinal polypeptide (VIP), somatostatin (SOM) or cholecystokinin (CCK). Examination of immunostained neurons demonstrated that most, if not all, of these peptide-containing cells correspond to spine-sparse class II neurons recognized in Golgi studies. Each type of peptide-containing perikaryon in BL exhibits a distinct size distribution which, in part, accounts for the broad size range of class II neurons noted in Golgi studies.     

Antinociception after microinjection of neurotensin into the central amygdaloid nucleus of the rat

Neurotensin (NT) is an endogenous peptide which has been hypothesized to function in the central nervous systems as a neurotransmitter. Injection of NT into the cerebral ventricular system of rodents produces antinociception in a variety of analgesia tests. In the hot plate test, direct microinjection of NT into the central nucleus of the amygdala (AC) produced a significant increase in the nociceptive threshold of the rat, while injections into tissue adjacent to the AC were generally ineffective. Antinociception following intra-AC injection of NT occurred at an ED₅₀ dose of 2.4 μg NT, and was significantly lower than the ED₅₀ dose observed when NT was given into the lateral ventricles (93.2 μg NT). Lesions of the stria terminalis totally abolished the antinociceptive effect of intra-AC administration of NT, indicating that AC efferent or afferent fibers within the stria terminalis are necessary for the observed increase in nociceptive threshold.     

A species-specific population of tyrosine hydroxylase-immunoreactive neurons in the medial amygdaloid nucleus of the Syrian hamster.

The medial amygdaloid nucleus (Me) is part of a neural pathway that regulates sexual behavior in the male Syrian hamster. To characterize the neurochemical content of neurons in this nucleus, brains from colchicine-treated adult male and female hamsters were immunocytochemically labeled using antibodies that recognize the catecholamine-synthesizing enzymes, tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT), as well as dopamine. A large population of TH-immunoreactive (TH-IR) neurons was observed throughout Me of male and female hamsters, primarily concentrated in the midrostral and caudal portions of the nucleus. The somata were generally small to medium in size and bipolar. Brains from animals that did not receive colchicine contained a limited number of TH-IR neurons in Me as reported previously. The DBH and PNMT antisera did not label any cells in Me of colchicine-treated animals, and the dopamine antiserum labeled neurons in the same location as the caudal group of TH-IR cells. Therefore, these caudal TH-IR neurons are interpreted to be dopaminergic. The rostral group of TH-IR neurons, on the other hand, may be producing only the immediate precursor of dopamine, L-3,4-dihydroxyphenylalanine (L-DOPA). The TH-synthesizing neurons in Me of the Syrian hamster appear to be a species-specific group of cells located outside of the previously described catecholaminergic cell groups.     

Transient tyrosine hydroxylase-like immunoreactive neurons contain somatostatin and substance P in the developing amygdala and bed nucleus of the stria terminalis of the rat

Tyrosine hydroxylase-like immunoreactive (TH-IR) neurons were observed from the embryonic day 17 (E17) to 6 weeks postnatally in two closely related nuclei of the limbic system, the bed nucleus of the stria terminalis (BNST) and the central nucleus of the amygdala (CNA) where they were restricted to circumscribed zones. These cells were scarce with an immature morphological aspect at E17. They progressively differentiated and increased in number until postnatal day 5 (P5), when their maximal density was reached. They were characterized as neurons by their ultrastructural appearance and the presence of both axo-somatic and axo-dendritic synaptic junctions. Moreover, TH-IR axons could be followed in the stria terminalis leaving the CNA, suggesting that part of TH-IR cells could be long projecting neurons rather than interneurons. A gradual decrease in the intensity of TH-IR and in density of labeled neurons was noted from P15 on, in both nuclei, (-50% at 4 weeks) until their total disappearance at 7 weeks. The significance of this TH-IR labeling regarding the catecholaminergic transmission remains unclear since these neurons did not contain the other catecholaminergic synthetic enzymes (DOPA-decarboxylase, dopamine-beta-hydroxylase, phenylethanolamine-N-methyl transferase) nor endogenous catecholamines. Double-labeling immunocytochemical methods, indicated that almost all the TH-IR neurons were colocalized with somatostatin 28 (SST) and with substance P (SP). Therefore these neurons expressed simultaneously 3 phenotypes, TH, SST and SP. This observation brings forth the notion of multiple neurotransmitter expression in transient neuronal populations and raises the question of neurotransmitter plasticity in the late postnatal development of the central nervous system (CNS). These neurons which were observed in two closely interconnected structures could be involved in early limbic circuits.     

Parabrachial inputs to Fos-immunoreactive neurons in the lateral central nucleus of amygdala activated by hypotension: a light and electron microscopic study in the rat

Morphological features and functional implications of projections of the parabrachial nucleus to the central nucleus of the amygdala were investigated in the rat. The anatomical study was based on injections of the tracers horseradish peroxidase and biotinylated dextran amine. An extremely dense concentration of labeled fibers was found in the lateral and lateral capsular subdivisions of the central nucleus of the amygdala, originating mainly from the external lateral and ventral lateral subnuclei of the parabrachial nucleus. The parabrachial fibers exhibited the morphological characteristic of forming dense pericellular terminal arborizations. The functional implications of this pathway in cardiovascular functions were verified using Fos protein induction in response to hypotension induced by continuous intravenous administration of hydralazine-hydrochloride. In this paradigm, Fos immunoreactivity was found to be confined to the lateral and lateral capsular subdivisions of the central nucleus of the amygdala. Double immunostaining methods were used to visualize, at the electron microscopic level, terminals labeled by biotinylated dextran amine and Fos cell labeling. With this approach, we were able to confirm that Fos-immunoreactive neurons in the central nucleus of the amygdala receive axosomatic terminals from the parabrachial nucleus. The present findings point out that parabrachial inputs to the central nucleus of the amygdala play a relevant role in regulating cardiovascular function.     

Electrophysiological characteristics of amygdaloid central nucleus neurons during Pavlovian fear conditioning in the rabbit

Recent evidence suggests that the amygdaloid central nucleus (ACE) may contribute importantly to cardiovascular adjustments in response to the presentation of conditioned emotional stimuli, possibly via direct ACE projections to cardiovascular regulatory nuclei in the medulla. The present experiment was conducted to obtain additional data relevant to this suggestion. Extracellular single-unit recordings were obtained from 85 histologically-verified ACE neurons during Pavlovian differentially conditioned heart-rate responding in rabbits. Conditioning involved pairing one tone (CS+), but not a second tone (CS-), with paraorbital shock. Those ACE neurons which project to the lower brainstem were identified by their antidromic responses to stimulation of a mesencephalic region through which descending ACE projections course. Under these conditions it was possible to classify ACE neurons as conforming to one of 6 general categories based on their spontaneous activity and conditioned response characteristics. In addition, it was determined that: (1) the electrophysiological characteristics of many ACE neurons were differentially altered in response to presentations of the CS+ versus the CS-; (2) the responses of many ACE neurons to presentations of the CS+ were correlated with the magnitudes of concomitant conditioned alterations in heart rate; and (3) the activity of antidromically-identified ACE neurons which project to the lower brainstem was decreased in response to presentations of each CS. These data provide additional support for the notion that the ACE contributes to cardiovascular regulation during the presentation of emotionally-arousing stimuli.     

Increase of tyrosine hydroxylase-like immunoreactive neurons in the nucleus accumbens and the olfactory bulb in the rat with the lesion in the ventral tegmental area of the midbrain

A small number of neurons in the nucleus accumbens of the rat showed tyrosine hydroxylase-like immunoreactivity (TH-LI). These TH-LI neurons had medium-sized cell bodies with several spiny dendrites. When a lesion was produced in the ventral tegmental area of the midbrain by injecting 6-hydroxydopamine, TH-LI neurons in the nucleus accumbens, as well as those in the olfactory bulb, were increased in number on the side ipsilateral to the lesion. The results indicated that expression of TH might be enhanced in some neurons deprived of dopaminergic afferent fibers.     

电刺激大鼠杏仁中央核对脑桥臂旁核味觉神经元的影响(英文)

利用电生理学方法观察了电刺激杏仁中央核对脑桥臂旁核味觉神经元的影响。结果表明 :电刺激杏仁中央核抑制大部分臂旁核味觉神经元的活动 ,并且提高臂旁核味觉神经元对五种基本味觉刺激反应的特异性。电刺激杏仁中央核对臂旁核的抑制作用以对盐酸和奎宁刺激的反应尤为明显 (P <0 .0 1) ,并且对这两种厌味刺激反应的抑制作用是基本一致的。本研究的结果提示 ,杏仁中央核可能通过抑制脑干味觉神经元对厌味刺激的反应 ,从而参与对摄食行为的调控     

电刺激大鼠杏仁中央核对脑桥臂旁核味觉神经元的影响

利用电生理学方法观察了电刺激杏仁中央核对脑桥臂旁核味觉神经元的影响.结果表明:电刺激杏仁中央核抑制大部分臂旁核味觉神经元的活动,并且提高臂旁核味觉神经元对五种基本味觉刺激反应的特异性.电刺激杏仁中央核对臂旁核的抑制作用以对盐酸和奎宁刺激的反应尤为明显(P＜0.01),并且对这两种厌味刺激反应的抑制作用是基本一致的.本研究的结果提示,杏仁中央核可能通过抑制脑干味觉神经元对厌味刺激的反应,从而参与对摄食行为的调控.     

Localization of mu-opioid receptors on amygdaloid projection neurons in the parabrachial nucleus of the rat.

The parabrachial nucleus (PB) is a major relay of noxious and non-noxious visceral sensory information from the nucleus of the solitary tract, spinal cord, and spinal trigeminal nucleus to the forebrain. The nucleus of the solitary tract, spinal cord, and trigeminal dorsal horns contain many enkephalin- and dynorphin-immunoreactive neurons that project to the PB. To study the role of mu-opioid receptors in relaying these inputs, we examined the distribution of mu-opioid receptor immunoreactivity in the PB. The most intense staining was in the external lateral parabrachial subnucleus (PBel), including dendrites extending from the PBel into the lateral crescent subnucleus. Because the Pbel is a major source of projections to the amygdala, we combined retrograde tracing from the central nucleus of the amygdala with immunohistochemistry for mu-opioid receptors. These experiments showed that mu-opioid receptors are expressed by Pbel neurons that project to the amygdala, including those Pbel neurons whose dendrites extend into the lateral crescent subnucleus. These results indicate that mu-opioid receptors in the PB may mediate or modulate nociceptive information relayed to the amygdala from medullary or spinal cord neurons that terminate not only in the Pbel, but also in the adjacent lateral crescent parabrachial subnucleus.     

Colocalization of tyrosine hydroxylase and GAD65 mRNA in mesostriatal neurons

Although dopamine has been considered as the only neurotransmitter in the nigrostriatal pathway, studies carried out in the last two decades have suggested the existence of a nondopaminergic nigrostriatal projection, and more recently, gamma-aminobutyric acid (GABA) has been identified as its neurotransmitter. In this study, we used the combination of immunocytochemistry for tyrosine hydroxylase (TH; a marker of dopaminergic neurons), in situ hybridization (ISH) for two different isoforms of glutamic acid decarboxylase (GAD65 and GAD67, the rate-limiting enzyme in GABA synthesis) and retrograde tracing techniques to investigate the possible existence of nigrostriatal neurons containing both neurotransmitters (dopamine and GABA) in the rat. Our results revealed that approximately 10% of mesostriatal dopaminergic neurons, most of them lying in the medial region of the substantia nigra pars compacta (SNC) and neighbouring A10 region, contain GAD65 mRNA. These findings reveal a third nigrostriatal pathway formed by dopaminergic/GABAergic neurons. Contrasting with the idea that in the basal ganglia, dopamine and GABA are released from different cell populations, the results suggest a more complex dopamine/GABA interaction than previously assumed, probably including cotransmission.