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PubMed2002

Dual innervation of the brachialis muscle.

A study of the innervation of the brachialis muscle was carried out on 45 male and 31 female Thai cadavers between the ages of 15 and 92 years (mean = 59 years). The dissections revealed that all brachialis muscles received innervation from the musculocutaneous nerve and that 81.6% were also innervated by a branch from the radial nerve. Among the brachialis muscles with a dual nerve supply, two patterns of branching from the radial nerve were observed: in one pattern the branch to the brachialis had a descending course (58%) and in the other pattern the nerve ascended or recurred (42%) to innervate the muscle. The radial nerve branch penetrated the inferolateral part of the brachialis muscle in 83% of cases (103/124) and its middle third in 17% of specimens (21/124). The basis for the dual innervation may result from fusion of two different embryonic muscular primordia: the ventral (flexor) and the dorsal (extensor) muscle masses. In contrast to a brachialis muscle innervated by the musculocutaneous nerve only, a muscle with dual innervation may be spared significant denervation by an anterior approach to the humerus through a longitudinally bisected muscle. In a dually innervated muscle, however, separation of the brachialis and brachioradialis muscles during surgery may put the radial nerve branch to the brachialis at risk.

Adolescent↗
PubMed2002

Developmental timing of hair follicle and dorsal skin innervation in mice.

The innervation of hair follicles offers an intriguing, yet hardly studied model for the dissection of the stepwise innervation during cutaneous morphogenesis. We have used immunofluorescence and a panel of neuronal markers to characterize the developmental choreography of C57BL/6 mouse backskin innervation. The development of murine skin innervation occurs in successive waves. The first cutaneous nerve fibers appeared before any morphological evidence of hair follicle development at embryonic day 15 (E15). Stage 1 and 2 developing hair follicles were already associated with nerve fibers at E16. These fibers approached a location where later in development the follicular (neural) network A (FNA) is located on fully developed pelage hair follicles. Prior to birth (E18), some nerve fibers had penetrated the epidermis, and an additional set of perifollicular nerve fibers arranged itself around the isthmus and bulge region of stage 5 hair follicles, to develop into the follicular (neural) network B (FNB). By the day of birth (P1), the neuropeptides substance P and calcitonin gene-related peptide became detectable in subcutaneous and dermal nerve fibers first. Newly formed hair follicles on E18 and P1 displayed the same innervation pattern seen in the first wave of hair follicle development. Just prior to epidermal penetration of hair shafts (P5), peptide histidine methionine-IR nerve fibers became detectable and epidermal innervation peaked; such innervation decreased after penetration (P7- P17). Last, tyrosine hydroxylase-IR and neuropeptide Y-IR became readily detectable. This sequence of developing innervation consistently correlates with hair follicle development, indicating a close interdependence of neuronal and epithelial morphogenesis.

Aging↗
PubMed2004

TrkC kinase expression in distinct subsets of cutaneous trigeminal innervation and nonneuronal cells.

Neurotrophin-activated receptor tyrosine kinases (Trks) regulate sensory neuron survival, differentiation, and function. To permanently mark cells that ever express TrkC-kinase, mice with lacZ and GFP reporters of Cre recombinase activity were crossed with mice having IRES-cre inserted into the kinase-containing exon of the TrkC gene. Prenatal reporter expression matched published locations of TrkC-expression. Postnatally, more trigeminal neurons and types of mystacial pad innervation expressed reporter than immunodetectable TrkC, indicating that some innervation transiently expresses TrkC-kinase. Reporter-tagged neurons include all those that immunolabel for TrkC, a majority for TrkB, and a small proportion for TrkA. TrkA neurons expressing TrkC-reporter range from small to large size and supply well-defined types of mystacial pad innervation. Virtually all small neurons and C-fiber innervation requires TrkA to develop, but TrkC-reporter is present in only a small proportion that uniquely innervates piloneural complexes of guard hairs and inner conical bodies of vibrissa follicle-sinus complexes. TrkC-reporter is expressed in nearly all presumptive Adelta innervation, which is all eliminated in TrkA knockouts and partially eliminated in TrkC knockouts. Many types of Abeta-fiber innervation express TrkC-reporter including all Merkel, spiny, and circumferentially oriented lanceolate endings, and some reticular and longitudinally oriented lanceolate endings. Only Merkel endings require TrkC to develop and survive, whereas the other endings require TrkA and/or TrkB. Thus, TrkC is required for the existence of some types of innervation that express TrkC, but may have different functions in others. Many types of nonneuronal cells affiliated with hair follicles and blood vessels also express TrkC-reporter but lack immunodetectable TrkC.

Animals↗
PubMed1978

The localization of the motor neurons innervating the extraocular muscles in the oculomotor nuclei of the cat and rabbit, using horseradish peroxidase.

The localization of the motor neurons innervating the extraocular muscles in the oculomotor nuclei of adult cats and rabbits was investigated by means of retrograde labelling with horseradish peroxidase (HRP). The groups consisting of the motor neurons innervating an individual muscle lay in the nucleus as elongated columns extending in a longitudinal direction. The position of each group in the transverse section varied according to the rostro-caudal level of the nucleus. In the cat and rabbit, entire contralateral innervation of the superior rectus and entire ipsilateral innervation of three muscles of the inferior rectus, medial rectus and inferior oblique were similarly observed. However, the arrangement of individual motor groups differed considerably in both animals except for the group innervating the inferior rectus which was generally found in the ventral position running through the rostral two-thirds of the oculomotor nucleus. In the case of cats, the central caudal nucleus bilaterally innervated the levator palpebrae superioris. The motor neurons innervating this muscle in the rabbit (which lacks the central caudal nucleus) formed a rostro-caudal club-shaped column close to the group innervating the superior rectus. The aberrant cellular mass in the adjoining medial longitudinal fasciculus which belongs to the medial rectus appears to play an important role in the eye movement, because it commonly appears in various animals.

Animals↗
PubMed1988

Sensory innervation of the hairs of the rat hindlimb: a light microscopic analysis.

The sensory innervation of the hair follicles of the furry skin of the rat hindlimb has been investigated by using the Winkelmann silver technique to stain peripheral axons and their terminals. This technique was found to stain only large- and medium-sized dorsal root ganglion cells and all laminae of the dorsal horn except lamina II, and therefore it is likely that, while A beta and A delta afferent fibres in the skin are stained, C fibres are not. Small vellus hairs were the commonest type of hair on the hindlimb particularly above the ankle. Many were not innervated. Those that were had lanceolate terminals arranged as palisades parallel to the hair shaft with circumferential presumptive Ruffini piloneural complexes and free nerve endings external to this. Circumferential innervation patterns without palisades were not uncommon but palisades without circumferential fibres were rare. Guard hairs which varied considerably in size were the next commonest hair type. Considerably more of these were innervated, by three-to-15 afferents forming both palisades of ten-to-30 lanceolate terminals and circumferential terminals. Both the innervated vellus and guard hairs had an associated vertical fibre projecting toward the epidermis. Tylotrichs, the largest hairs on the hindlimb, were rare (1-2%) and were only found above the ankle, but all were densely innervated by many axons. A prominent single nerve contributed to an annular complex by forming a bilaminar arrangement of lanceolate and circumferential terminals within the outer connective tissue sheath. Each tylotrich had an associated Merkel cell-neurite complex (haarscheiben). Differences in the distribution, innervation density, and phase in the growth cycle of the different hair types were found for skin from different regions of the hindlimb, which, together with the extent of the polyneuronal innervation of most follicles, has important implications for the processing by the somatosensory system of the afferent input generated by brushing hairs.

Afferent Pathways↗
PubMed1990

Simultaneous labeling of vagal innervation of the gut and afferent projections from the visceral forebrain with dil injected into the dorsal vagal complex in the rat.

The vagal innervation of the different layers of the rat gastrointestinal wall was identified with the fluorescent carbocyanine dye Dil, injected into the dorsal motor nucleus of the vagus (dmnX). Multiple, bilateral injections were used to label all dmnX preganglionic motoneurons, and as a consequence, most of the vagal primary afferents that terminate in the adjacent nucleus of the solitary tract (nts) were also retrogradely and transganglionically labeled. With Fluorogold used to label the enteric nervous system completely and specifically, the Dil-labeled vagal profiles could be visualized and quantified in their anatomical relation to the neurons of the myenteric and submucous ganglia. In the myenteric plexus, vagal fibers and terminals were found throughout the gastrointestinal tract as far caudal as the descending colon, but there was a general decreasing proximodistal gradient in the density of vagal innervation. All parts of the gastric myenteric plexus (fundus, corpus, antrum), as well as the proximal duodenum, were extremely densely innervated, with vagal fibers and terminals in virtually every ganglion and connective. Further caudally, both the percentage of innervated myenteric ganglia and the average density of label within the ganglia rapidly decreased, with the exception of the cecum and proximal colon, where up to 65% of the ganglia were innervated. In the gastric and duodenal submucosa very few and in the mucosa no vagal fibers and terminals were found. With both normal epifluorescence and laser scanning confocal microscopy, highly varicose or beaded terminal structures of various size and geometry could be identified. The Dil injections, which impregnated the dmnX as well as the adjacent nts, resulted in retrograde and anterograde labeling of all the previously reported forebrain connections with the dorsal vagal complex. We conclude that the myenteric plexus is the primary target of vagal innervation throughout the gastrointestinal tract, and that its innervation is more complete than previously assumed. In contrast, vagal afferent (and efferent) innervation of mucosa and submucosa seems conspicuously sparse or absent. Furthermore, the use of more focal injections of Dil offers the prospect to simultaneously identify specific subsets of vagal preganglionics and their central nervous inputs.

Animals↗
PubMed1991

Serotoninergic innervation of the ferret cerebral cortex. I. Adult pattern.

We have investigated the serotoninergic innervation of the adult ferret cerebral cortex with immunohistochemical techniques. Distribution pattern of serotoninergic fibers in the ferret neocortex is characterized by a decrease in the density of fibers as one moves from the pial surface towards the white matter. Throughout the entire cerebral cortex, the serotoninergic fibers are very dense within the supragranular layers, especially within layer 1. In contrast, granular and infragranular layers exhibit only a sparse innervation. Although this general pattern of innervation is roughly the same in all cortical areas, significant variations in the fiber density are apparent in different regions. Areas 17, 1, 6, and 8 (primary visual cortex, presumptive somatosensory cortex, presumptive motor cortex, and prefrontal cortex, respectively) are described in more detail to illustrate the diversity of the serotoninergic innervation patterns. The density of innervation is highest in areas 1 and 6, intermediate in area 8, and lowest in area 17. It is noteworthy that while areas 1, 6, and 8 show a marked decrease in fiber density at the boundary between layer 3 and 4, the less strongly innervated area 17 shows a change in density in the transition from layer 2 to layer 3. The types of fibers found within the ferret cortex are similar to those described in other mammalian species. The bulk of the innervation is made by very fine fusiform axons with small ovoid varicosities. In addition to this fiber type, axons with thick round varicosities and some smooth nonvaricose axons were found. The latter types occur in very small numbers within the supragranular layers and mostly in more anterior cortical regions. While the general innervation pattern and the fiber types are similar to those described in the cat cerebral cortex, the pericellular baskets found in the cat cortex (Mulligan and Törk, J Comp Neurol 270:86-110, 1988) are not seen in the ferret.

Animals↗
PubMed1994

Development of fungiform papillae, taste buds, and their innervation in the hamster.

Fungiform taste buds in mature hamsters are less subject to neurotrophic influences than those of other species. This study evaluates taste-bud neurotrophism during development in hamsters by examining the relation between growing nerves and differentiating fungiform papillae. Chorda tympani (CT) or lingual (trigeminal) nerve (LN) fibers were labelled with Lucifer Yellow as they grew into (CT fibers) or around (LN fibers) developing taste buds. Developing fungiform papillae and taste pores were counted with the aid of a topical tongue stain. The tongue forms on embryonic days (E) 10.5-11 and contains deeply placed CT and LN fibers but no papillae. By E12, the tongue epithelium develops scattered elevations. These "eminences" selectively become innervated by LN fibers that grow to the epithelium earlier and in larger numbers than CT fibers. Definitive fungiform papillae form rapidly during E13-14 and become heavily innervated by LN fibers. Intraepithelial CT fibers, rare at E13, invariably innervate fungiform papillae containing nascent taste buds at E14. During E14-15 (birth = E15-16), most papillae contain taste buds with pores, extensive perigemmal LN innervation, and extensive intragemmal CT innervation. At birth, numbers of fungiform papillae and taste pores are adultlike. The results show that fungiform eminences begin forming in the absence of innervation. The subsequent differentiation of definitive fungiform papillae and their innervation by LN fibers occur synchronously, prior to the differentiation of taste buds and their CT innervation. The hamster is precocious (e.g., compared to rat) in terms of LN development and the structural maturity of the anterior tongue at birth.

Animals↗
PubMed1994

Innervation of laryngeal nerve paraganglia: an anterograde tracing and immunohistochemical study in the rat.

Carotid body-like organs, paraganglia, frequently occur in the superior and recurrent laryngeal nerves. The paraganglia are supplied with a rich innervation of unknown origin. In the present study, the origin of the innervation of the paraganglia of the rat was studied with two different techniques. One approach was anterograde tracing of wheat-germ agglutinin-horseradish peroxidase after injection into the nodose and jugular ganglia of the vagus and the superior cervical ganglion. The other approach was immunohistochemical staining for neuropeptides after excision of the superior cervical ganglion, or vagotomy. Antisera against neuropeptide Y, vasoactive intestinal polypeptide, and calcitonin gene-related peptide were utilized. Both the tracing method and calcitonin gene-related peptide immunohistochemistry after vagotomy showed that the paraganglia receive sensory innervation from the vagal ganglia. No labeling was detected in the paraganglia after injection of wheat-germ agglutinin-horseradish peroxidase in the superior cervical ganglion. Excision of this ganglion did not lead to a decrease in the neuropeptide-Y innervation in the paraganglia, but most of this innervation in the surrounding blood vessels disappeared. The observations show that the superior cervical ganglion does not contribute to the innervation in the paraganglia and that the neuropeptide-Y innervation of the blood vessels originates from the superior cervical ganglion whereas that of the paraganglia has another origin, most likely local ganglionic cells. The results also suggest that the vasoactive intestinal polypeptide innervation in the paraganglia arises from local ganglionic cells. The two approaches complemented each other in mapping the afferent and efferent nerve supply of the paraganglia.

Animals↗
PubMed1995

Differential innervation of protruder and retractor muscles of the tongue in rat.

Protrusion and retraction of the tongue are essential components of such orofacial behaviors as mastication, respiration, and swallowing. Stimulation of the medial branch of the hypoglossal nerve yields tongue protrusion, while stimulation of the lateral branch yields tongue retraction in rat. We exploited the transsynaptic transport capabilities of pseudorabies virus to determine specific circuits that innervate protruder and retractor muscles of the rat tongue. Each group of muscles is innervated by distinct populations of hypoglossal motoneurons: caudal ventral and ventrolateral motoneurons form the largest proportion of those innervating protruders, whereas rostral dorsal motoneurons innervate retractors. Our primary finding was differential innervation of protruder and retractor motoneurons by premotoneurons in the lateral tegmental field: premotoneurons innervating protruder motoneurons were more ventral and ventromedial than those innervating retractor motoneurons. In addition, protruder motoneurons received projections from the ipsilateral lateral parabrachial nucleus but not spinal trigeminal nucleus or medial and ventral subnuclei of the solitary tract; the converse was true for retractor motoneurons. These results suggest segregation of functional networks that control hypoglossal motoneurons. The dorsal medulla, in or around the solitary tract, contains neurons specific to retractor motoneurons, and the region ventrolateral to the hypoglossal nucleus contains circuitry specific to protruder motoneurons. Common innervation of medial and lateral branch motoneurons is provided by premotoneurons in the raphe and gigantocellular reticular formation of the medial medulla. The midline medullary nuclei with diverse projections may coordinate complex behavior or modulate general motoneuron excitability, whereas the lateral reticular formation, with anatomically discrete projections, may control motoneurons that contribute to distinct orofacial behaviors.

Animals↗
PubMed1980

Segmental innervation of rotated and supernumerary axolotl hindlimbs.

The segmental nerve supply to axolotl limbs was misrouted by severing the limbs at the level of the femur, rotating them 180 degrees around their long axis, and then suturing them to the intact proximal stump. Following return of the blood supply to the rotated limb by the cross-anastomosing of blood vessels, a blastema often formed to the side of the rotation site giving rise to a supernumerary limb. The muscles of both rotated and supernumerary limbs were innervated by the segmental nerves. The percentage of cells innervated by segmental nerves 16 and 17 in each muscle was determined with intracellular electrodes at 14 weeks after the operation. Despite histological evidence that nerves had been misrouted in the rotated limb, the percentage innervation of each muscle by nerves 16 and 17 was similar to that in the unoperated contralateral controls. The same results were obtained for the supernumerary limbs. In some muscles a few synaptic sites were found innervated by segmental nerves which did not innervate that muscle in the contralateral controls. These had synaptic potentials with very low quantal contents if immediately adjacent sites were innervated by the segmental nerve, which did innervate that muscle in the contralateral controls. The results suggest that the selective properties of synaptic sites are alone sufficient to determine the entire segmental innervation pattern of the muscles in a limb.

Ambystoma↗
PubMed1983

Can differences in limb regeneration ability between individuals within certain amphibian species be explained by differences in the quantity of innervation?

In some species of amphibians, the regenerative response to limb amputation is not uniform. For example, regenerative ability varies from one individual to another within the species Xenopus laevis, Ambystoma maculatum, and Amphiuma tridactylum. In many species, limb regenerative ability declines with increasing age. The objective of this investigation was to determine if this variation in regenerative ability can be explained by variation in the quantity of innervation. In each of the above-named species, limbs were amputated and allowed to regenerate. The quantity of innervation (percentage of cross-sectional area of amputated surface occupied by nerves) was measured in the amputated part of the limb as close as possible to the amputation surface. The presence, rate, or extent of limb regeneration in that specific limb was then compared to the quantity of innervation at the amputation surface. The results indicated that there was no correlation between innervation and the rate or extent of regeneration in Xenopus laevis or Ambystoma maculatum. On the other hand, in Amphiuma tridactylum, those limbs that regenerated were the ones that had the highest levels of innervation. In Ambystoma maculatum, the quantity of innervation was measured at five different stages, from early larvae to mature adult. The results showed that the quantity of innervation was highest during the larval period, reaching a maximum at the late larval stage before declining greatly to the adult level. It appears that the decline in regenerative ability in the adult cannot be attributed solely to a reduction in innervation to below the threshold level.

Age Factors↗
PubMed1983

Spatial organization in the saccule and lagena of a teleost: hair cell pattern and innervation.

The relationship between the hair cell orientation pattern and innervation in the saccule and lagena of the teleost Helostoma temmincki (the kissing gourami) was investigated with scanning electron microscopy and the Winkelmann-Schmitt silver impregnation technique. The hair cell pattern in the saccule consists of four orthogonally oriented groups. The anterior two groups are oriented along the animal's rostrocaudal axis, and the posterior two are oriented along its dorsoventral axis. The pattern of hair cell orientations in the lagena is a typical bidirectional one. Two divisions of the eighth nerve innervate the saccule. The anterior division innervates the horizontally oriented hair cell groups, and the posterior division innervates the dorsoventrally oriented groups. A single nerve innervates the lagena, with the majority of fibers innervating one or the other of the two lagenar hair cell groups. The segregated pattern of innervation according to hair cell orientation groups in the saccule was confirmed in other species. Individual types of axonal terminations appear to innervate hair cells of specific ciliary bundle types.

Animals↗
PubMed2001

Sodium influx during action potential in innervated and denervated rat skeletal muscles.

Resting Na(+) influx (J(i)(Na)) was measured in innervated and denervated (1-6 days) rat extensor digitorum longus muscle in the absence and presence of 2 micromol/L tetrodotoxin (TTX). The mean value of Na(+) permeability (P(Na)) in innervated muscles was 49.6 +/- 2.6 pm.s(-1). At the second day postdenervation, it decreased by about 45%. This was followed, between the second and fourth days, by a sharp rise, which by the sixth day reached a steady value approximately 2.5 times greater than that of innervated muscles. This, most likely, generated the 30% increase in internal [Na(+)] concentration ([Na(+)](I)) observed at this time. Tetrodotoxin reduced P(Na) of both innervated and denervated muscles by about 25%. In 6-day denervated muscles, virtually all the TTX effect on P(Na) represents the blockage of TTX-resistant Na(+) channels. Denervation produced a depolarization of about 20 mV by the sixth day. The extra J(i)(Na) per action potential (AP) decreased monotonically with time after denervation from 20.0 +/- 3.8 in innervated to 11.1 +/- 1.0 nmol.g(-1).AP(-1) in 6-day denervated muscles. The overshoot of the AP decreased from 15 +/- 1 in innervated to 7 +/- 1 mV in 6-day denervated muscles. Likewise, the maximum rate of rise (+dV/dt), an expression of the inward Na(+) current, fell from 305 +/- 14 in innervated to 188 +/- 18 V.s(-1) in 6-day denervated muscles. The estimated 6-day denervated/innervated ratio of peak Na(+) conductance (g(Na)) was 0.67. The changes in AP parameters promoted by denervation were substantially reduced when both innervated and denervated fibers were hyperpolarized to -90 mV. These results suggest that the depolarization, mainly due to the increase in P(Na) /P(K) ratio, increases Na(+) inactivation and consequently reduces peak g(Na), in spite of the absolute increment in resting TTX-sensitive P(Na). This, in addition to the moderate reduction in the inward driving force on Na(+), decreases the inward Na(+) current and the extra J(i)(Na) per AP.

Action Potentials↗
PubMed1991

Elevated levels of polyneuronal innervation persist for as long as two years in reinnervated frog neuromuscular junctions.

When the nerve to an adult frog sartorius muscle is crushed, and axons are allowed to regenerate, the level of polyneuronal innervation at reinnervated neuromuscular junctions is higher than normal. With time, much of this polyneuronal innervation is reduced by the process of synapse elimination (Werle and Herrera, 1988). Using intracellular recording, we estimated the level of polyneuronal innervation in adult frog (Rana pipiens) sartorius muscles 2 years (range: 1.7-2.4 years) after crushing the sartorius nerve. We found that 27% (S.E. = 1.4%) of the junctions in muscles 2 years after reinnervation were polyneuronally innervated, whereas only 10% (S.E. = 1.2%) of the junctions in normal frog muscles were polyneuronally innervated. Thus, the synapse elimination that occurs following reinnervation does not restore the normal level of polyneuronal innervation. Histological comparisons of junctional structure between muscles 2 years after reinnervation and normal muscles revealed substantial differences. Reinnervated junctions had a greater length of synaptic gutter apposed by nerve terminal processes, more axonal inputs, more empty synaptic gutter, more instances of single synaptic gutters innervated by more than one axon, and longer lengths of nerve terminal processes that connect synaptic gutters within a junction. On the basis of this physiological and anatomical evidence, we conclude that nerve injury causes persistent changes in the pattern of muscle innervation.

Animals↗
PubMed2000

Cell types required to efficiently innervate human muscle cells in vitro.

Previous studies carried out in our laboratory have shown that myofibers formed by fusion of muscle satellite cells from donors with spinal muscular atrophy (SMA) type I or II undergo a characteristic degeneration 1.5-3 weeks after innervation with rat embryonic spinal cord explants. The only cells responsible for degeneration of innervated cocultures are SMA muscle satellite cells. In order to study the kinetics of nerve and muscle cell degeneration in nerve-muscle cocultures implicating SMA muscle cells, we attempted to simplify the nervous component of the coculture and identify the nerve cell types necessary for a successful innervation. We demonstrate here that motoneurons alone were unable to innervate myotubes. However, when three cell types (motoneurons, sensory neurons, and Schwann cells) were added onto a reconstituted muscular component consisting of cloned muscle satellite cells and cloned muscular fibroblasts, myotubes contracted, indicating that functional neuromuscular junctions were formed. We concluded that the three cell types were required for a successful innervation. Moreover, we studied the effects of culture medium conditioned by different combinations of nerve cells on innervation; we observed that physical contacts among sensory neurons, motoneurons, and myotubes are required for a successful innervation; in contrast Schwann cells can be replaced by a Schwann-cell-conditioned medium, indicating that these cells produce a putative soluble "innervation-promoting factor." Obviously such a reconstituted system does not reflect the in vivo situation but it allows the formation of functional motor synapses and could therefore allow us to elucidate neuromuscular disease pathogenesis, especially that of spinal muscular atrophy.

Adolescent↗
PubMed1976

Trans-synaptic regulation of the development of end organ innervation by sympathetic neurons.

To examine the regulation of development of end organ innervation the superior cervical ganglion (SCG), and two of its target organs, the iris and pineal gland, were studied using biochemical and histofluorescent approaches. During postnatal ontogeny the activity of tyrosine hydroxylase (T-OH), which is localized to adrenergic neurons, increased 50-fold in iris, and 34-fold in pineal nerve terminals of the rat. These increases paralleled the in vitro rise in iris [3H]norepinephrine ([3H]NE) uptake, a measure of the presence of functional nerve terminal membrane. These biochemical indices of end organ innervation correlated well with developmental increases in density of innervation, adrenergic ground plexus ramification and nerve fiber fluorescence intensity as determined by fluorescence microscopy. Unilateral transection of the presynaptic cholinergic nerves innervating the SCG in 2-3-day-old rats prevented the normal development of end organ innervation: T-OH activity, [3H]NE uptake, innervation density, plexus ramification and fluorescence intensity failed to develop normally in irides innervated by decentralized ganglia. It is concluded that trans-synaptic factors regulate the maturation of adrenergic nerve terminals, and the development of end organ innervation by SCG.

Animals↗
PubMed1992

Immune system of the spontaneously hypertensive rat. I. Sympathetic innervation.

Extensive bidirectional interactions are believed to exist between the sympathetic nervous system and the immune system. The spontaneously hypertensive rat (SHR) is known to possess both increased sympathetic nervous system activity with increased tissue catecholamine levels in several peripheral organs and a moderate T lymphocyte immune deficiency. We examined the development of innervation in both primary (thymus) and secondary (spleen) organs of the immune system of the SHR compared to immunocompetent Wistar-Kyoto (WKY), Fisher 344 (F-344), and Long Evan (LE) rats from birth through 24 weeks. Using glyoxylic acid-induced histofluorescence to visualize monoaminergic nerve fibers, coded specimens were examined and morphologically evaluated for the extent and distribution of innervation. The innervation of the SHR thymus was significantly increased at 2 and 12 weeks of age over the other strains. Unlike the control strains, splenic innervation in SHR was delayed until 2 weeks of age when it suddenly became exuberant. At 12 weeks, the innervation of the SHR spleen was increased over all control strains. By 24 weeks the innervation had regressed to a level comparable to the levels of the other rat strains in these tissues. During the suckling period, the size (weight) of the WKY spleen was larger and the level of innervation was decreased compared to the other strains. These strain-related differences in the development of sympathetic innervation of thymus and spleen likely reflect the complex, bidirectional interplay between the nervous and the immune systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗