Pericellular Baskets Research Articles

Nuclear organization and morphology of catecholaminergic neurons and certain pallial terminal networks in the brain of the Nile crocodile, Crocodylus niloticus

In the current study, we use tyrosine hydroxylase (TH) immunohistochemistry to detail the nuclear parcellation and cellular morphology of neurons belonging to the catecholaminergic system in the brain of the Nile crocodile. In general, our results are similar to that found in another crocodilian (the spectacled caiman) and indeed other vertebrates, but certain differences of both evolutionary and functional significance were noted. TH immunopositive (TH+) neurons forming distinct nuclei were observed in the olfactory bulb (A16), hypothalamus (A11, A13-15), midbrain (A8-A10), pons (A5-A7) and medulla oblongata (area postrema, C1, C2, A1, A2), encompassing the more commonly observed nuclear complexes of this system across vertebrates. In addition, TH + neurons forming distinct nuclei not commonly identified in vertebrates were observed in the anterior olfactory nucleus, the pretectal nuclear complex, adjacent to the posterior commissure, and within nucleus laminaris, nucleus magnocellularis lateralis and the lateral vestibular nucleus. Palely stained TH + neurons were observed in some of the serotonergic nuclei, including the medial and lateral divisions of the superior raphe nucleus and the inferior raphe and inferior reticular nucleus, but not in other serotonergic nuclei. In birds, a high density of TH + fibres and pericellular baskets in the dorsal ventricular ridge marks the location of the nidopallium caudolaterale (NCL), a putative avian analogue of mammalian prefrontal cortex. In the dorsal ventricular ridge (DVR) of the crocodile a small region in the caudolateral anterior DVR (ADVRcl) revealed a slightly higher density of TH + fibres and some pericellular baskets (formed by only few TH + fibres). These results are discussed in an evolutionary and functional framework.

Cholecystokinin immunoreactive neurons in the basolateral amygdala of the rhesus monkey (Macaca mulatta).

Several distinct subpopulations of interneurons (INs) in the amygdalar basolateral nuclear complex (BNC) of the rat can be recognized on the basis of their expression of calcium-binding proteins and neuropeptides, including parvalbumin (PV), somatostatin (SOM), calretinin (CR), and cholecystokinin (CCK). In the rat BNC CCK is expressed in two separate IN subpopulations, termed large (CCKL ) and small (CCKS ). These subpopulations exhibit distinct connections indicative of discrete functional roles in the circuitry of the BNC. Although there have been several studies of PV+, SOM+, and CR+ INs in the primate BNC, there is almost no information regarding CCK+ INs in these species. Therefore, in the present study the distribution and morphology of CCK+ INs and their axon terminals in the BNC of the monkey was investigated. CCK immunoreactivity in the BNC was observed in somata and proximal dendrites of nonpyramidal neurons, as well as in axon terminals. A moderate density of CCK+ INs was found in all nuclei of the BNC. CCK+ INs in the BNC were morphologically heterogeneous, with both small and large varieties observed. All CCK+ somata gave rise to 2-4 dendrites that branched sparingly and were aspiny. CCK+ axon terminals in the BNC were found both in the neuropil and forming pericellular baskets contacting somata of pyramidal cells. In addition, many CCK+ neurons were contacted by multiple CCK+ terminals, indicative of the existence of a CCK interneuronal network. These data indicate that the morphology of CCK+ INs in the monkey is very similar to that of the rat.

P.6.b.006 mGluR5 receptors on neurons expressing D1 dopamine receptors control escalation of alcohol drinking after abstinence

The lateral septum (LS) plays a role in the adjustment of behavioral responses according to environmental demands. This is a complex integrative process wherein a variety of modulatory systems, i.e. cholinergic, dopaminergic and serotonergic projections forming pericellular baskets around LS neurons, are involved.Recently, vesicular glutamate transporter 3 (VGLUT3)-immunoreactive (-ir) structures outlining unlabeled somata and their proximal dendrites were described in the LS. However, the vesicular transporters for acetylcholine and GABA were not or only rarely co-expressed with VGLUT3.In this study, the morphology and distribution of these VGLUT3-ir structures were systematically analyzed revealing that (1) they form distinct pericellular baskets (PBs) displaying variable shapes, (2) they are arranged in a layer-like pattern similar to the terminals of other modulatory systems, (3) beside a few exceptions (e.g., choline acetyltransferase), they are generally not or very sparsely co-localized with other neurochemical markers characterizing major neuron populations or afferent systems of the LS, i.e. calcium-binding proteins, tyrosine hydroxylase, tryptophan hydroxylase, vesicular glutamate transporters 1 (VGLUT1) and 2 (VGLUT2) and the vesicular GABA transporter.Thus, in the LS, a separate population of neurons is covered by VGLUT3-ir PBs. The distribution pattern and the lack of co-localization indicate that the VGLUT3-expressing cells of origin are located in the brainstem and that they could be pure glutamatergic projection neurons—different from the well-defined canonical VGLUT1- and VGLUT2-expressing neurons. Alternatively, they could simultaneously express VGLUT3 and second transmitter, but use different release sites inside the LS for both.

Cocaine- and amphetamine-regulated transcript (CART) peptide- immunopositive neuronal elements in the lateral septum: Rostrocaudal distribution in the male rat

The morphological features and distribution of cocaine- and amphetamine-regulated transcript peptide immunoreactivity (CART-IR) were studied in the lateral septum (LS) of male rats using light and electron microscopic immunocytochemistry and computer-aided densitometry. CART-IR was detected along the rostrocaudal axis of the LS in varicose axonal fibers only, although immunoreactive cell bodies and dendrites were not detected. Pericellular basket-like arrangements around immunonegative cell bodies were present. From among the targets of such pericellular baskets, glutamic acid decarboxylase (GAD)-immunopositive and NPY-immunoreactive somata were identified. Thin varicose axons were present in each section, whereas thick varicose axons were restricted to the sections of rostral position only. CART-IR was observed in varicose fibers forming a dense subependymal plexus, from which solitary varicose fibers entered the ependymal layer. The fine structure of varicosities was similar to that of other neuropeptide-containing fibers. Small varicosities established asymmetrical synaptic contacts mainly with dendrites and dendritic spines, and larger varicosities established symmetrical synapses with somata and dendritic shafts. CART-to-CART connections were not revealed. The density curve of the CART-IR along the rostrocaudal axis of LS was found to be paraboloid. CART is known as one of the most anorexigenic peptides. These results serve as basis for further physiological studies concerning the biological significance of lateral septal CART peptide in the regulation of food intake.

Vesicular glutamate transporter 3-immunoreactive pericellular baskets ensheath a distinct population of neurons in the lateral septum

The lateral septum (LS) plays a role in the adjustment of behavioral responses according to environmental demands. This is a complex integrative process wherein a variety of modulatory systems, i.e. cholinergic, dopaminergic and serotonergic projections forming pericellular baskets around LS neurons, are involved. Recently, vesicular glutamate transporter 3 (VGLUT3)-immunoreactive (-ir) structures outlining unlabeled somata and their proximal dendrites were described in the LS. However, the vesicular transporters for acetylcholine and GABA were not or only rarely co-expressed with VGLUT3. In this study, the morphology and distribution of these VGLUT3-ir structures were systematically analyzed revealing that (1) they form distinct pericellular baskets (PBs) displaying variable shapes, (2) they are arranged in a layer-like pattern similar to the terminals of other modulatory systems, (3) beside a few exceptions (e.g., choline acetyltransferase), they are generally not or very sparsely co-localized with other neurochemical markers characterizing major neuron populations or afferent systems of the LS, i.e. calcium-binding proteins, tyrosine hydroxylase, tryptophan hydroxylase, vesicular glutamate transporters 1 (VGLUT1) and 2 (VGLUT2) and the vesicular GABA transporter. Thus, in the LS, a separate population of neurons is covered by VGLUT3-ir PBs. The distribution pattern and the lack of co-localization indicate that the VGLUT3-expressing cells of origin are located in the brainstem and that they could be pure glutamatergic projection neurons—different from the well-defined canonical VGLUT1- and VGLUT2-expressing neurons. Alternatively, they could simultaneously express VGLUT3 and second transmitter, but use different release sites inside the LS for both.

Differential RIP antigen (CNPase) expression in peripheral ensheathing glia

The RIP monoclonal antibody is commonly used to identify oligodendrocytes. Recently, the RIP antigen was identified as 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), a known non-compact myelin protein [Watanabe, M., Sakurai, Y., Ichinose, T., Aikawa, Y., Kotani, M., Itoh, K., 2006. Monoclonal antibody Rip specifically recognizes 2′,3′-cyclic nucleotide 3′-phosphodiesterase in oligodendrocytes. J. Neurosci. Res. 84, 525–533]. In the present study we characterize normal and axotomy-induced changes in RIP immunoreactivity in peripheral glia. In myelinating Schwann cells, RIP demarcated paranodal regions of myelinated axons and clearly defined Schmidt–Lantermann incisures. Surprisingly, RIP immunoreactivity was not confined to myelinating glia. Robust RIP immunoreactivity was present in Remak bundles in mixed nerves and in sympathetic ganglia and grey rami. Following peripheral nerve injury, RIP immunoreactivity was redistributed diffusely throughout de-differentiating Schwann cell cytoplasm. In uninjured rats, low levels of RIP immunoreactivity were detectable in satellite cells surrounding dorsal root ganglion (DRG) neurons and in terminal Schwann cells at neuromuscular junctions. This pattern suggested a correlation between RIP immunoreactivity and the amount of axon–glial contact. We therefore injured the L5 spinal nerve to induce sympathetic sprouting and pericellular basket formation in the DRG, and asked whether relatively RIP-negative satellite glia, which normally contact only neuronal somata, would upregulate the RIP antigen upon contact with sprouting sympathetic axons. All perineuronal sympathetic sprouts infiltrated heavily RIP-immunoreactive satellite cell sheaths. RIP immunoreactivity was absent from placode-derived olfactory ensheathing glia, indicating that the relationship between axon–glial contact and RIP-immunoreactivity is restricted to peripheral ensheathing glia of the neural crest-derived Schwann cell lineage.

Cocaine- and amphetamine-related transcript peptide and somatostatin in rat intracardiac ganglia

The distribution of somatostatin and cocaine and amphetamine-regulated transcript (CART) was investigated in rat intracardiac ganglia. Somatostatin immunoreactivity was only present in nerve terminals, always colocalised with choline acetyltransferase immunoreactivity, surrounding approximately 10% of intracardiac neurons. Somatostatin-immunoreactive terminals particularly targeted intrinsic cardiac neurons that were immunoreactive for calbindin. Somatostatin was also present in sympathetic cholinergic neurons in the stellate ganglia, but could not be detected in neurons of the nucleus ambiguus and dorsal motor nucleus of the vagus in the brainstem. CART immunoreactivity was present in 46% of intracardiac neuronal somata, including those that expressed either NOS or calbindin immunoreactivity but was never present in terminals forming pericellular baskets around intracardiac neurons. CART immunoreactivity was absent from sympathetic cell bodies in the stellate ganglia, but was present in nerve terminals around sympathetic neurons. Based on the results of this study, additional chemical diversity was identified among elements of the rat cardiac nervous system that may define neural pathways of different function.

Extrinsic and intrinsic sources of calcitonin gene-related peptide immunoreactivity in the lamb ileum: a morphometric and neurochemical investigation

To investigate extrinsic origins of calcitonin gene-related peptide immunoreactive (CGRP-IR) nerve fibres in the sheep ileum, the retrograde fluorescent tracer Fast Blue (FB) was injected into the ileum wall. Sections of thoraco-lumbar dorsal root ganglia (DRG) and distal (nodose) vagal ganglia showing FB-labelled neurons were processed for CGRP immunohistochemistry. The distribution of CGRP-IR in fibres and nerve cell bodies in the ileum was also studied. CGRP-IR enteric neurons were morphometrically analysed in myenteric (MP) and submucosal plexuses (SMP) of lambs (2-4 months). Sensory neurons retrogradely labelled with FB were scattered in T5-L4 DRG but most were located at the upper lumbar levels (L1-L3); only a minor component of the extrinsic afferent innervation of the ileum was derived from nodose ganglia. In the DRG, 57% of retrogradely labelled neurons were also CGRP-IR. In cryostat sections, a dense network of CGRP-IR fibres was observed in the lamina propria beneath the epithelium, around the lacteals and lymphatic follicles (Peyer's platches), and along and around enteric blood vessels. Rare CGRP-IR fibres were also present in both muscle layers. Dense pericellular baskets of CGRP-IR fibres were observed around CGRP-negative somata. The only CGRP-IR nerve cells were well-defined Dogiel type II neurons localised in the MP and in the external and internal components of the SMP. CGRP-IR neurons in the myenteric ganglia were significantly larger than those in the submucosal ganglia (mean profile areas: about 1,400 mum(2) for myenteric neurons, 750 mum(2) for submucosal neurons). About 6% of myenteric neurons and 25% of submucosal neurons were CGRP-IR Dogiel type II neurons. The percentages of CGRP-IR neurons that were also tachykinin-IR were about 9% (MP) and 42% (SMP), whereas no CGRP-IR neurons exhibited immunoreactivity for vasoactive intestinal peptide, nitric oxide synthase or tyrosine hydroxylase in either plexus. Thus, CGRP immunoreactivity occurs in the enteric nervous system of the sheep ileum (as in human small intestine and MP of pig ileum) in only one morphologically defined type of neuron, Dogiel type II cells. These are probably intrinsic primary afferent neurons.

Preferential localization of the hyperpolarization‐activated cyclic nucleotide‐gated cation channel subunit HCN1 in basket cell terminals of the rat cerebellum

Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are involved in the control of neuronal excitability and plasticity. In this study, we used immunoblotting and immunohistochemical techniques to reveal the developmental expression and subcellular distribution of the HCN1 subunit in the cerebellar cortex. During postnatal development, the spatio-temporal expression of HCN1 correlated well with the morphological events occurring during the ontogenesis of cerebellar interneurons. Using immunoblotting techniques, HCN1 was weakly detected during the first postnatal week and continued to increase throughout postnatal development, peaking at postnatal day (P)15. At the light-microscopic level, HCN1 immunoreactivity was very weak until P7 whereas from P10-12 to adulthood it was strongly detected in the lower third of the molecular layer and in the Purkinje cell layer. HCN1 was present in axons running through the molecular layer and in the pericellular basket around Purkinje cells at P12, but in the periaxonal plexus (the pinceau) surrounding their initial segment only after P15. Using immunofluorescence, HCN1 colocalized with GAD65 and synaptophysin, demonstrating that the subunit was present in inhibitory axons and axon terminals. At the electron-microscopic level, in adulthood, HCN1 immunoparticles were detected at postsynaptic sites in basket and Purkinje cells but most immunoparticles were found at presynaptic sites in basket cell axons and in terminals. In the axon terminals, the distribution of HCN1 was relatively uniform along the extrasynaptic plasma membrane; this was confirmed using quantitative techniques. The present findings suggest that HCN1 channels may provide a significant route for modulating co-ordinated cerebellar synaptic transmission through basket cells.

Immunohistochemical analysis of intracardiac ganglia of the rat heart.

The neurochemistry of intracardiac neurons in whole-mount preparations of the intrinsic ganglia was investigated. This technique allowed the study of the morphology of the ganglionated nerve plexus found within the atria as well as of individual neurons. Intracardiac ganglia formed a ring-like plexus around the entry of the pulmonary veins and were interconnected by a series of fine nerve fibres. All intracardiac neurons contained immunoreactivity to PGP-9.5, choline acetyl transferase (ChAT) and neuropeptide Y (NPY). Two smaller subpopulations were immunoreactive to calbindin or nitric oxide synthase. Furthermore, a subpopulation (approximately 6%) of PGP-9.5/ChAT/NPY-immunoreactive cells lacking both calbindin and nitric oxide synthase (NOS) was surrounded by pericellular baskets immunoreactive to ChAT and calbindin. Vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activated peptide (PACAP), substance P and tyrosine hydroxylase (TH) immunoreactivity was observed in nerve fibres within the ganglion, but never in neuronal somata. Furthermore, immunoreactivity for NPY was not observed in pericellular baskets surrounding intracardiac neurons, despite being present in all intrinsic neuronal cell bodies. Taken together, the results of this study indicate a moderate level of chemical diversity within the intracardiac neurons of the rat. Such chemical diversity may reflect functional specialisation of neurons in the intracardiac ganglia.

Molecular plasticity of primary nociceptive neurons: relations of the NGF- c-jun system to neurotomy and chronic pain

Neurotomy is widely used as a model of chronic, intractable pain, the proverbial "crux medicorum". Immunohistochemical aspects of this chronic pain model are discussed in this paper, with the aim of shedding new light on the pathomechanism and possible therapeutical consequences. Central terminals of nociceptive neurons contain substance P, somatostatin and calcitonin generelated peptide or exhibit fluoride resistant acid phosphatase and thiamine monophosphatase enzyme reaction in the superficial dorsal horn of the spinal cord and in analogous structures of the brain stem. These neuropeptides and neuroproteins are expressed by the related dorsal root ganglion cells and transported via orthograde axoplasmic transport via dorsal roots to the central nervous system. Transection of the ipsilateral, segmentally related peripheral sensory nerve results in transganglionic degenerative atrophy of central terminals of primary nociceptive neurons. Transganglionic degenerative atrophy is characterized by marked ultrastructural alterations superficially similar to, but essentially differing from the signs of Wallerian degeneration which ensue after dorsal rhizotomy. Transganglionic degenerative atrophy is accompanied by depletion of marker neuropeptides and enzymes, and later by the expression of vicarious neuropeptides such as vasoactive intestinal polypeptide, neuropeptide Y and galanin and of the enzyme choline acetyl transferase. Consequences of blockade of retrograde axoplasmic transport of the nerve growth factor elicited either by perineural application of microtubule inhibitors or by perineural administration of anti-nerve growth factor are similar to peripheral neurotomy. According to recent studies described in this paper, the blockade of nerve growth factor supply to primary nociceptive neurons induces activation of c-jun in nuclei of primary nociceptive neurons probably responsible for the plasticity of the neuropeptide and neuroprotein synthesizing machinery. In contrast, invasion of and formation of pericellular baskets by noradrenergic axons can be elicited only by axotomy and not by blockade of retrograde axoplasmic transport. Involvement of nerve growth factor and the nerve growth factor-dependent immediate early genes in neuroplasticity of neuropeptidergic primary sensory neurons raise the possibility of a gene therapy of chronic intractable pain.

Chemical coding of sympathetic neurons controlling the tarsal muscle of the rat

Sympathetic axons in the upper eyelid and in tissues in the superior retro-orbital space were examined for NPY immunoreactivity. Sympathetic nerve terminals containing co-localised NPY were associated with blood vessels, the conjunctiva and the Meibomian glands. The acini of the Harderian gland completely lacked sympathetic innervation. Sympathetic axons lacking NPY were only found in the tarsal muscle. In addition, a minority of terminals, located in the more proximal part of the tarsal muscle, contained weak immunoreactivity to NPY. Injections of the retrograde tracer, Fast Blue, into the eyelid or retro-orbital space labelled postganglionic somata in the superior cervical ganglion. While many retrogradely labelled somata were immunoreactive for NPY, around half lacked NPY immunoreactivity and so are likely to project to the tarsal muscle. Most of the retrogradely labelled postganglionic somata lacking NPY were surrounded by terminals immunoreactive for met-enkephalin, leu-enkephalin and met-enkephalin arg-gly-leu which were all found to be present in the same nerve terminals. Sectioning the cervico-sympathetic trunk eliminated all enkephalin-immunoreactive pericellular baskets. Many enkephalin-immunoreactive pericellular terminals contained co-localised VAChT, calretinin and calbindin immunoreactivity, but completely lacked nitric oxide synthase immunoreactivity. A second population of nerve terminals that were immunoreactive for nitric oxide synthase also surrounded tarsal muscle-projecting neurons, but these terminals lacked immunoreactivity to enkephalin. Thus, postganglionic neurons projecting to the tarsal muscle are of at least two chemical phenotypes (with or without NPY) and they receive convergent input from at least two populations of preganglionic neurons with distinctive chemical phenotypes.

Synaptic connections of distinct interneuronal subpopulations in the rat basolateral amygdalar nucleus.

Although it is well established that the activity of pyramidal projection neurons in the basolateral amygdala (ABL) is controlled by gamma-aminobutyric acid (GABA)ergic inhibitory interneurons, very little is known about the connections of specific interneuronal subpopulations in this region. In the present study, immunohistochemical techniques were used at the light and electron microscopic levels to identify specific populations of interneurons and to analyze their connections with each other and with unlabeled presumptive pyramidal neurons. Double-labeling immunofluorescence experiments revealed that antibodies to vasoactive intestinal peptide (VIP) and calbindin-D28K (CB) labeled two separate interneuronal subpopulations in the ABL. Light microscopic double-labeling immunoperoxidase experiments demonstrated that many VIP-positive (VIP+) axon terminals formed intimate synaptic-like contacts with the CB-positive (CB+) neurons and that both CB+ and VIP+ terminals often contributed to the formation of pericellular baskets that surrounded unlabeled perikarya of pyramidal neurons. By using a dual immunoperoxidase/immunogold-silver procedure at the ultrastructural level, it was found that 30% of VIP+ terminals in the anterior subdivision of the basolateral nucleus innervated interneurons that were either CB+ (25%) or VIP+ (5%). A smaller percentage (15%) of CB+ terminals formed synapses with labeled interneurons. Both VIP+ and CB+ terminals also innervated unlabeled perikarya, dendrites, and spines, most of which probably belonged to pyramidal neurons. The interconnections between interneurons may be important for disinhibitory mechanisms and the mediation of rhythmic oscillations in the ABL.

Evidence that nerve growth factor mediates the formation of sensory pericellular baskets in the rat trigeminal ganglion

A role for nerve growth factor (NGF) in the remodeling of sensory neurons in the trigeminal ganglion was examined. Intracerebroventricular NGF infusion and/or bilateral removal of the sympathetic superior cervical ganglia, both of which are believed to increase the availability of NGF to primary sensory neurons, resulted in a significant increase in the frequency of calcitonin gene-related peptide immunoreactive pericellular baskets. The results of this study suggest that increased NGF is sufficient to enhance the formation of sensory baskets in this ganglion, and provide evidence that NGF may mediate the formation of sensory baskets in the sensory ganglia following injury.

Innervation of guinea-pig stellate ganglia by nitric oxide synthase, cocaine- and amphetamine-regulated transcript protein- and pituitary adenylate cyclase activating polypeptide-immunoreactive fibers

The present study analyzed using immunohistochemical labeling the distribution and co-localization of nitric oxide synthase (NOS), cocaine- and amphetamine-regulated transcript peptide (CARTp) and pituitary adenylate cyclase activating polypeptide (PACAP) with choline acetyltransferase (ChAT)-immunoreactive fibers in the guinea-pig stellate ganglia. ChAT-immunoreactive fibers make pericellular baskets around virtually all stellate ganglia neurons. Pericellular baskets of NOS, CARTp and PACAP fibers were also present around numerous stellate ganglia neurons. Although all the NOS and PACAP fibers also exhibited ChAT immunoreactivity, only some of the CARTp fibers were ChAT-immunoreactive. No evidence of co-localization of NOS, PACAP and CARTp was obtained. These results indicate that NOS, PACAP and CARTp are present in distinct preganglionic axons innervating the guinea-pig stellate ganglia.

Effect of Peripheral Nerve Lesion and Lumbar Sympathectomy on Peptide Regulation in Dorsal Root Ganglia in the NGF-Overexpressing Mouse

Galanin is a peptide normally expressed at low levels both in sensory and in sympathetic neurons. It is strongly upregulated after peripheral nerve lesions, and it has been proposed that nerve growth factor (NGF) plays a role in this regulation. In the present study the effect of both sciatic nerve transection and lumbar sympathectomy on galanin in lumbar dorsal root ganglia (DRGs) was examined in mice overexpressing NGF (NGFOE) in the skin under the keratin promoter. The superior cervical ganglia (SCG) were also studied. In the DRG pericellular baskets containing tyrosine hydroxylase- (TH) and galanin-like immunoreactivity (LI) were found, mostly in the same fibers. Galanin-positive baskets were also found in the trigeminal ganglia. However, only single neuropeptide Y (NPY)-positive baskets were observed within the DRGs. No marked difference in number of galanin-positive neurons was seen between wild-type and NGFOE mice. After sciatic nerve transection galanin was upregulated in DRG neurons to about the same extent in NGFOE mice as in wild-type mice. Galanin-, but not TH-LIs decreased in the pericellular baskets. After lumbar sympathectomy both galanin- and TH-immunoreactive baskets disappeared, suggesting a sympathetic origin. In the SCG the very low galanin mRNA levels were strongly increased after lesion of the carotid nerves, both in wild-type and in NGFOE mice. However, whereas NPY mRNA levels decreased in the SCG after axotomy in the wild-type mice, there was a distinct increase in the NGFOE mice. Our results show that high NGF levels in skin induce formation of pericellular baskets in DRGs expressing galanin- and TH-LI and that galanin in these baskets is strongly influenced by peripheral axotomy. However, overexpression of NGF did not markedly influence galanin expression in DRG neurons, neither normally nor after nerve lesions. Finally, expression of NPY in sympathetic ganglia is differently regulated in NGFOE compared to wild-type mice.

Parvalbumin-containing neurons in the rat basolateral amygdala: morphology and co-localization of Calbindin-D 28k

Parvalbumin is a calcium-binding protein that is contained in certain neuronal populations in the brain. Although the exact function of parvalbumin is not clear, it has been found to be a useful marker for studying the connections of specific cell types in immunohistochemical studies. In the present investigation immunohistochemical techniques were used to study the morphology of parvalbumin-containing neurons in the rat basolateral amygdala. These neurons were found to be a morphologically heterogeneous subpopulation of non-pyramidal interneurons. Parvalbumin-positive axons in the basolateral amygdala were observed to form “pericellular baskets” that enveloped the perikarya of pyramidal neurons. In addition, some parvalbumin-immunoreactive axons formed “cartridges” that appeared to surround non-immunoreactive processes. The morphology of parvalbumin-positive neurons closely resembled that of neurons containing calbindin, a related calcium-binding protein. Analysis of adjacent sections stained for each protein using the mirror technique revealed that approximately 80% of parvalbumin neurons also contained calbindin, and that approximately 60% of calbindin neurons also contained parvalbumin. This study demonstrates that parvalbumin-containing neurons constitute an important subpopulation of non-pyramidal interneurons in the rat basolateral amygdala. The axonal configurations of these cells indicate that they may exert a potent inhibitory influence over pyramidal projection neurons. We suggest that parvalbumin-containing neurons can control emotional responses mediated by the basolateral amygdala by controlling the output from this important brain region.

Remodeling of adult sensory axons in the superior cervical ganglion in response to exogenous nerve growth factor

In previous studies, we found that a 2-week in vivo intracerebroventricular infusion of nerve growth factor (NGF) elicited a sprouting response by sympathetic perivascular axons associated with the intradural segment of the internal carotid artery. We hypothesized that NGF infused into the ventricular system would be internalized by responsive sympathetic cerebrovascular axons, retrogradely transported to parent cell bodies in the superior cervical ganglion (SCG), and subsequently released into the local ganglionic environment. Because fibers exhibiting immunoreactivity for calcitonin gene related peptide (CGRP) have been localized in the SCG, we used immunohistochemical methods to investigate whether a response by CGRP-immunoreactive axons in the SCG occurred following the proposed transport to and release of exogenous NGF in the ganglion. In consecutive tissue sections of the SCG stained for either CGRP or NGF, we found CGRP pericellular ‘baskets’ surrounding identified NGF-immunoreactive cell bodies. Nerve growth factor infusion resulted in a significant increase both in the number of CGRP pericellular baskets and in NGF-immunoreactive cell bodies. A significant positive correlation ( r=0.95, P<0.05) between the pericellular baskets and NGF-immunoreactive cell bodies was observed, suggesting that intracranial projection neurons in the SCG released infused NGF (or possibly a converted signal) into the local ganglionic environment to elicit remodeling of CGRP fibers to form pericellular baskets. These findings were confirmed in sections double labeled for NGF and CGRP immunoreactivity. This remodeling suggests that exogenous NGF may mediate retrograde transneuronal plasticity, allowing for future in vivo examinations of the mechanisms involved in neurotrophin transport and release.

Evidence that dopaminergic axons provide a dense innervation of specific neuronal subpopulations in the rat basolateral amygdala

Dopaminergic inputs from the ventral tegmental area and substantia nigra are involved in numerous emotional and behavioral functions mediated by the amygdala. Previous studies have shown that some dopaminergic axons selectively innervate subpopulations of neurons in the rat basolateral amygdala by forming dense pericellular arrays (baskets) that envelope the perikarya of these neurons. Because of the obvious functional significance of this innervation, a sequential two-color immunoperoxidase technique was used in the present study to determine which neuronal subpopulations are targeted. Pericellular baskets were seen in sections stained for tyrosine hydroxylase, but not for dopamine-beta-hydroxylase, suggesting that these axonal arrays are dopaminergic. Most baskets enveloped small ovoid or piriform perikarya, although a few in the anteroventral part of the basolateral nucleus were associated with larger pyramidal cells. Double-labeling immunohistochemistry revealed that all of the smaller baskets enveloped a subpopulation of parvalbumin-immunoreactive nonpyramidal neurons, but not nonpyramidal neurons containing vasoactive intestinal polypeptide or neuropeptide Y. Since these parvalbumin containing neurons are known to be GABAergic interneurons, the results of this study suggest that the actions of dopamine in the basolateral amygdala are mediated, in part, by a subpopulation of inhibitory interneurons.

Chemically distinct preganglionic inputs to iris-projecting postganglionic neurons in the rat: A light and electron microscopic study

Individual autonomic postganglionic neurons are surrounded by pericellular baskets of preganglionic terminals that are easily identifiable with the light microscope. It has been assumed that the target cell of a pericellular basket of preganglionic terminals is the neuron at the centre of the basket. This assumption has enabled the connectivity of preganglionic neurons to be determined at the light microscopic level. However, if the preganglionic terminals in a pericellular basket make synapses with the dendrites of nearby, but functionally different, postganglionic neurons, then the conclusions of light microscopic studies are far less certain. We have used a serial section ultrastructural study to determine the target of the preganglionic pericellular basket in a situation where the apparent target cell is surrounded by neurons of dissimilar function. In the rat superior cervical ganglion, postganglionic neurons projecting to the iris were identified, using retrograde tracers, as single neurons (i.e., not in clusters). We have used immunohistochemistry to show that iris-projecting neurons are surrounded by preganglionic nerve terminals containing calcitonin gene-related peptide (CGRP). We have demonstrated that the pericellular basket of CGRP-immunoreactive preganglionic terminals provides inputs only to the soma at the centre of the basket and not to the dendrites of surrounding neurons. This suggests that, in autonomic ganglia, light microscopic identification of the preganglionic terminal baskets is likely to be a reliable method for identifying the targets of subclasses of preganglionic neurons.