Autonomic innervation of the urogenital system: adrenergic and cholinergic elements

The major organs of the male urogenital (UG) system have been examined in various mammals, including man, using light and electron microscopic (EM) histochemical methods. For the light microscopic study, the urinary bladder, the vas deferens and the penis (corpora cavernosa and corpus spongiosum) were studied in the rat, cat, dog, monkey and man using a glyoxylic acid (GA) method modified for peripheral adrenergic nerve fibers, and a thiocholine method for acetylcholinesterase (AChE). Fine structural analysis was done on the vasa of rat, cat, monkey and man, and on the bladder and penis of cat, dog, monkey and man. Tissue was fixed in glutaraldehyde (GMO) as a control or in glutaraldehyde-dichromate (GDC) for the specific localization of norepinephrine (NE). All organs studied demonstrated numerous adrenergic nerve fibers throughout the muscular layers, in the connective tissue, and in the adventitia of most blood vessels. These fibers had a brilliant fluorescence when visualized with the GA method, and demonstrated many varicosities with small (400–600 A) and/or large (800–1200 A) granular vesicles in both control and GDC-fixed tissue examined with the EM. Evaluation of the vesicles with the analytical electron microscope (AEM) verified that those in the GDC-fixed tissue were chrome-positive, and, therefore, NE-containing. In the vas and penis, acetylcholinesterase(AChE)-positive nerve fibers were encountered less frequently at the light microscopic level than adrenergic fibers, and few typical cholinergic varicosities were seen in these organs with the EM. In the bladder, cholinergic nerves were seen with about the same frequency as adrenergic fibers in both light microscopic and EM preparations. Also observed frequently in each of the viscera were varicosities with large to very large (800–2000 A) granular vesicles of the kind presently hypothesized to be peptidergic or purinergic. Few varicosities of the type considered sensory, with large (800–1200 A) clear vesicles and numerous mitochondria, were observed in this tissue. Evidence from this study suggests that mammalian UG organs are innervated extensively by adrenergic nerves, and, excepting the bladder, have a limited cholinergic innervation; in the bladder, numerous fibers of each type can be found. In addition, another type of nerve fiber, perhaps peptidergic or purinergic, is found in large numbers in each of the organs studied and thus may represent a significant effector of autonomie regulation.     

Regeneration of perivascular adrenergic innervation in rat tibial nerve after nerve crush

Summary Adrenergic innervation of blood vessels in the rat tibial nerve during degeneration and regeneration was studied using the formaldehyde-induced fluorescence method. The left sciatic nerve was crushed with suture threads to produce a 4-mm length of crushed nerve. At 1, 3, 7, 14, 28, 56 and 84 days after nerve crush, degenerative and regenerative changes in the nerve were verified using light microscopy. At each time point, adrenergic innervation was examined in epi-perincurial whole mount and nerve cross-section preparations. One day after nerve crush, fluorescence of adrenergic nerve fibers in the endoneurium was absent. Fluorescent adrenergic nerve fibers reappeared in the endoneurium at day 56 and reached the control density by 84 days. In the epi-perineurium, adrenergic innervation of small and medium-size arterioles was absent at 3 days, in large arterioles at 7 days. At 56 days, all epi-perineurial arterioles were reinnervated by a faint, sparse adrenergic network, which reached the control density at 84 days. The results suggest that adrenergic innvervation in the rat peripheral nerve is lost during nerve degeneration, but recovers when the nerve has regenerated.     

Adrenergic innervation of blood vessels in rat tibial nerve during Wallerian degeneration

Summary Adrenergic innervation of blood vessels in rat tibial nerve during Wallerian degeneration was examined, using the formaldehyde-induced histo-fluorescence method. The left sciatic nerve was transected at the level of the sciatic notch, whereas the right sciatic nerve was left intact and used as control. At 1, 3, 7, 14, 42, 56 or 84 days after transection, the tibial nerves of the transected and contralateral sides were exposed. Pieces of each nerve were used for light microscopy or for examination of adrenergic innervation with the fluorescence microscope. One day after transection, no adrenergic nerve fiber was observed in the endoneurium of the transected nerve. After 3 days, adrenergic innervation of small-and medium-sized arterioles in the epi-perineurium was absent, and after 7 days no fibers were visible around large arterioles. Fluorescent fibers were not detected even at 84 days post-surgery. It is concluded that adrenergic innervation of blood vessels in the rat tibial nerve is irreversibly lost after permanent axotomy, and that adrenergic regulation of nerve blood flow may also be lost.     

Fluorescence histochemical methods for the study of peptide hormone-producing cells

Fluorescence histochemical methods for the demonstration of specific residues in peptides and proteins are reviewed: Formaldehyde-ozone for NH2-terminal tryptophan, formaldehyde-HCl for tryptophan regardless of position in the peptide, OPT for NH2-terminal histidine, formaldehyde-fluorescamine for "protected" amino groups, nitroso-naphthol for tyrosine, and phenanthrenequinone for arginine residues. The methods are potent in demonstrating granule-stored material in peptide hormone-producing cells. Also quinacrine, the fluorescent anti-malaria agent, binds to granular components, as yet unidentified, in several endocrine cell types. In many cases the fluorescence histochemical methods seem to demonstrate peptides and proteins distinct from the known hormones.     

Mechanisms of regrowth in the bulbospinal serotonin system following 5,6-dihydroxytryptamine induced axotomy. II. Fluorescence histochemical observations

The degenerative and regenerative processes following 75 μg 5,6-dihydroxytryptamine (5,6-DHT) have been investigated in the bulbospinal serotoninergic system with a fluorescence histochemical technique. Acutely, 1–3 weeks after 5,6-DHT an extensive disappearance of serotoninergic terminals was observed in the spinal gray, inferior olive, and the facial and hypoglossal nuclei, while the spinal trigeminal nucleus and regions of the reticular formation were partially denervated. Concomitantly, large numbers of swollen, highly fluorescent profiles, interpreted as the proximal stumps of lesioned serotoninergic axons, appeared in the medulla oblongata and most rostral cervical spinal cord. The first signs of regenerative sprouting from the swollen proximal stumps appeared one week after 5,6-DHT, and was prominent during subsequent weeks. The rate of reinnervation of different target areas was dependent on the distance to the regrowing axons; it was most rapid in brain stem nuclei. About one month after 5,6-DHT a terminal plexus of normal density had reappeared in both inferior olive and the facial nucleus. The axonal proliferation continued, however, to produce increasingly abnormal hyperinnervations. Certain abnormalities in terminal fiber morphology occurred: the fibers were coarser and exhibited higher fluorescence than normal, and in the facial and motor trigeminal nuclei rather thick, smooth fibers with pericellular arrangement appeared after long survival times (7–19 months). The reinnervation of spinal cord followed a slower time course. A normal amount of innervation was only reformed in the rostral 3–4 mm of the cervical spinal cord, while thoracic and lumbar levels only recovered a small part of the original terminal density.The regenerative growth demonstrated a high degree of specificity, which indicates precise mechanisms of guidance and recognition. These are presumably similar, or identical, to those regulating ontogenetic development of the serotoninergic system. Limitations of these regulatory mechanisms were, however, demonstrated both by the abnormal proximo-distal distribution of regenerated terminals, and in the inferior olivary complex, where the regrowing fibers invaded areas normally devoid of serotoninergic innervation. It is suggested that the drive of axonal growth is derived from an inherent program of the serotoninergic neurons to establish a predetermined amount of axonal arborizations. The role of the target tissue may be a mere provision of cues for recognition. The regulatory neuronal program seems to lack a mechanism to terminate further proliferation when an innervation of normal density has been reformed.     

Origin and termination of the diencephalo-spinal dopamine system in the rat

Using a combination of neonatal 6-hydroxydopamine and adult 5,7-dihydroxytryptamine treatment we have been able to achieve a 94–99% depletion of noradrenaline in the spinal cord. In such animals the dopamine levels are only marginally affected in the dorsal horn (at all levels) and in the intermediate zone at thoraco-lumbar levels. This combined treatment thus offers new possibilities for selective studies of the spinal dopamine projection. In agreement with the biochemical data the fluorescence histochemistry shows that the spinal dopamine innervation is mainly confined to the dorsal horn, the intermediolateral cell column and associated parts of the intermediate and central gray. Injections of fluorescent retrograde tracer combined with monoamine fluorescence histochemistry reveal that the diencephalic A11 cell group is the principal, and perhaps exclusive, source of this innervation. The area of termination, as well as the organizational similarities with certain diencephalic peptide-containing projections to the spinal cord, suggest that the diencephalo-spinal dopamine system may be importantly involved in autonomic regulatory processes.     

Noradrenergic sympathetic innervation of the spleen: IV. Morphometric analysis in adult and aged F344 rats

Noradrenergic postganglionic sympathetic innervation of the spleen in 8-month-old (adult) and 27-month-old (aged) Fischer 344 (F344) rats was examined using fluorescence histochemistry for catecholamines coupled with stereologic point-counting analysis for quantitation of noradrenergic varicosities. Noradrenergic varicosities in the spleen were evaluated in four compartments: (1) vascular-, (2) trabecular-, (3) capsular-, and (4) parenchymal-associated fibers. The 27-month-old rats were subdivided further into two groups based upon behavioral testing for gustatory neophobia, a condition reported to be associated with acute locus coeruleus lesions in young rats and with diminished norepinephrine (NE) levels in central noradrenergic neurons in aged rats. In the 8-month-old rats, spleens displayed abundant innervation. Noradrenergic plexuses entered the spleen with the splenic artery and its branches, distributed into capsular and trabecular compartments, and followed the vasculature and trabeculae into splenic white pulp. Noradrenergic fibers entered the white pulp mainly in association with the central artery and its branches; liner and punctate varicosities branched mainly from vascular plexuses into the large, well-defined parenchyma of the white pulp, ending primarily among fields of T lymphocytes. Some fibers extended along the inner edge of the marginal zone and the parafollicular zone. Few noradrenergic varicosities were found in the red pulp. In both groups of aged rats, sympathetic noradrenergic innervation was diminished markedly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Autoradiographic observations on the innervation of the carotid body of the domestic fowl

Tritiated leucine was injected into the distal vagal ganglion of 11 domestic fowl, which survived for 12-24 h under general anaesthesia. The cells of this ganglion are known to be exclusively afferent. EM autoradiography showed that in all 11 birds the vast majority of the silver grains fell upon the nervous tissues of the carotid body. In 5 of these birds a quantitative analysis was made, using point-counting morphometry. The incidence of silver grain per unit area was found to be 26 times greater in axonal endings than in the non-nervous components, and 15 times greater in axons in transit than in non-nervous components. The difference in incidence per unit area between these nervous and non-nervous components was highly significant (P less than 0.001). Of all the observed axonal endings 77% were labelled, but there is evidence that this is a substantial underestimate of the total population of afferent endings; in one bird 88% of the endings were labelled. Of the axons in transit, 18% were labelled. This low value is believed to be related to transfer of the label to the axonal endings by the fast component of axonal transport. Afferent and reciprocal synapses occurred in labelled axonal endings, which were therefore considered to have an afferent function. 'Efferent' type synapses also occurred in labelled endings, and therefore belonged to axons which in fact were afferent in function. It is concluded that the innervation of the carotid body of the domestic fowl is almost entirely afferent, the nerve cell bodies being in the distal vagal ganglion. Only very few efferent axonal endings are present. Ultrastructural features, including synaptic morphology, appear to constitute unreliable criteria for distinguishing between afferent and efferent axonal endings in the carotid body.     

Origin of cingulate cortex cholinergic innervation in the rat

The relative contribution of the n. diagonal band and thalamic nuclei to the cholinergic innervation of the cingulate cortex was examined. Lesions were placed in the n. diagonal band, anterior thalamus, and medial thalamus of rats, and changes in choline acetyltransferase in discrete regions of the cingulate cortex were determined. The n. diagonal band lesion produced a large decrease in choline acetyltransferase activity while the thalamic lesions produced no significant change in activity.     

Monoamine oxidase activity in noradrenaline neurons of the locus coeruleus of the rat. A double-labeling histochemical study

The aim of the present study is to examine whether noradrenergic neurons of the locus coeruleus (LC) of the rat contain monoamine oxidase (MAO) activity. Sections were processed initially for MAO enzyme histochemistry using tyramine as a substrate, followed by fluorescence immunohistochemistry for tyrosine hydroxylase (TH). In the LC, virtually all TH-immunoreactive neurons (i.e., noradrenergic neurons) were also positive for MAO. No MAO activity was found in any TH-negative neurons. Neurons in the LC have previously been shown to form dopamine during noradrenaline biosynthesis and to produce serotonin from exogenously administered -5-hydroxytryptophan. Moreover, dopamine- and serotonin-degrading MAO activity has also been found in LC neurons. Therefore, our results indicate that MAO activity is localized within noradrenergic neurons in the LC and is likely involved in the degradation of dopamine that is endogenously synthesized, and also in the elimination of serotonin that is produced from exogenous precursors.     

Comprehensive immunofluorescence and lectin binding analysis of intervibrissal fur innervation in the mystacial pad of the rat

The innervation of the intervibrissal fur in the mystacial pad of the rat and mouse was examined by immunofluorescence with a wide variety of antibodies for neuronal related structural proteins, enzymes, and peptides as well as for lectin binding histofluorescence with Griffonia simplicifolia (GSA). Anti-protein gene product 9.5 (PGP) immunofluorescence labeled all sets of axons and endings. The innervation in the upper dermis and epidermis was distributed through a four tiered dermal plexus. From deep to superficial, the second tier was the source of all apparent myelinated mechanorceptors, the third tier of nearly all the peptidergic and GSA binding innervation, and the fourth tier of nonpeptidergic GSA negative innervation (peptide-/GSA-). Three types of mechanoreceptors—Merkel, transverse lanceolate, and longitudinal lanceolate endings—innervated guard hair follicles. All had similar labeling characteristics for 160 kDa and 200 kDa neurofilament subunits, peripherin, carbonic anhydrase, synaptophysin, and S100. Palisades of longitudinal lanceolate endings were part of piloneural complexes along circumferentially oriented sets of transverse lanceolate endings, peptidergic free nerve endings (FNEs), and peptide-/GSA- FNEs. The longitudinal lanceolate endings were the only mechanoreceptors in the mystacial pad that had detectable calcitonin gene-related peptide. The epidermis contained four types of unmyelinated endings: simple free nerve endings (FNEs), penicillate endings, cluster endings and bush endings. Only the simple FNEs were clearly peptidergic. Virtually all others were peptide-/GSA-. Each bush ending was actually an intermingled cluster of endings formed by several unmyelinated axons and occasionally an Aδ axon. In contrast to the other unmyelinated innervation to the epidermis, bush endings labeled with an antibody against the Schwann cell protein S100. The necks and mouths of follicles, as well as superficial vasculature, were innervated by a mixture of unmyelinated peptidergic and/or GSA labeled sensory and sympathetic axons. Small presumptive sweat glands were innervated by three sets of peptidergic axons of which one was immunoreactive for somatostatin. Potential functions of the various sets of innervation are discussed. J. Comp. Neurol. 385:185–206, 1997. © 1997 Wiley-Liss, Inc.     

Polyneural innervation in the psoas muscle of the developing rat

Polyneural innervation was studied in the psoas muscle in developing rats from P4 till P25 and at adult age, with the combined silver–acetylcholinesterase technique. Nerve endings were counted, and end-plates were measured. These data were compared with such data in the human. The end of polyneural innervation in the rat (around P20) and in the human (around 12 weeks postterm age) in both cases coincides with a transformation in motor behavior and postural control. The rat's psoas muscle at early stages is less heavily innervated than this muscle in the human. Up to three axons per motor end-plate were counted at P4, but in the human up to five axons at 25 weeks of post menstrual age. This difference might be related to the lower percentage of type I muscle fibers in the rat. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:1058–1063, 1998.     

Comprehensive immunofluorescence and lectin binding analysis of vibrissal follicle sinus complex innervation in the mystacial pad of the rat

The innervation of the vibrissal follicle sinus complexes (FSCs) in the mystacial pad of the rat was examined by lectin binding histofluorescence with the B subunit of Griffonia simplicifolia (GSA) and by immunofluorescence with a wide variety of antibodies for neuronal related structural proteins, enzymes, and peptides. Only anti-protein gene product 9.5 labeled all sets of innervation. Several types of mechanoreceptors were distributed to specific different targets by medium to large caliber myelinated axons. All were positive for 200 kDa neurofilament subunit, peripherin, and carbonic anhydrase. Their endings expressed synaptophysin. Labeling for the 160 kDa neurofilament subunit, calbindin, and parvalbumin varied. Anti-Schwann cell protein S100 was completely co-extensive with the axons, terminal arbors, and endings of the mechanoreceptor afferents including Merkel innervation. At least 15 different sets of unmyelinated innervation were evident based upon distribution and labeling characteristics. They consisted of four basic types: 1) peptidergic; 2) GSA binding; 3) peptidergic and GSA binding; and 4) nonpeptidergic and GSA negative (peptide-/GSA-). Previous studies had not revealed that several major sets of unmyelinated innervation were peptide-/GSA-. The unmyelinated innervation had detectable peripherin but not 160 kDa or 200 kDa neurofilament subunits. GSA-positive axons uniquely lacked anti-S100 immunoreactivity. The dense circumferentially oriented unmyelinated innervation of the inner conical body contained major sets of peptide-/GSA- and GSA innervation as well as a smaller peptidergic GSA component. A small contingent of sympathetic and possibly parasympathetic innervation was affiliated with microvasculature in the FSCs. This study confirms and refutes some previous hypotheses about biochemical and morphological relationships between peripheral innervation and sensory ganglion cells. J. Comp. Neurol. 385:149–184, 1997. © 1997 Wiley-Liss, Inc.     

Similarities and differences in the innervation of mystacial vibrissal follicle-sinus complexes in the rat and cat: a confocal microscopic study

Our confocal three-dimensional analyses revealed substantial differences in the innervation to vibrissal follicle-sinus complexes (FSCs) in the rat and cat. This is the first study using anti-protein gene product 9.5 (PGP9.5) immunolabeling and confocal microscopy on thick sections to examine systematically the terminal arborizations of the various FSC endings and to compare them between two species, the rat and the cat, that have similar-appearing FSCs but different exploratory behaviors, such as existence or absence of whisking. At least eight distinct endings were clearly discriminated three dimensionally in this study: 1) Merkel endings at the rete ridge collar, 2) circumferentially oriented lanceolate endings, 3) Merkel endings at the level of the ring sinus, 4) longitudinally oriented lanceolate endings, 5) club-like ringwulst endings, 6) reticular endings, 7) spiny endings, and 8) encapsulated endings. Of particular contrast, each nerve fiber that innervates Merkel cells at the level of the ring sinus in the rat usually terminates as a single, relatively small cluster of endings, whereas in the cat they terminate en passant as several large clusters of endings. Also, individual arbors of reticular endings in the rat ramify parallel to the vibrissae and distribute over wide, overlapping territories, whereas those in the cat ramify perpendicular and terminate in tightly circumscribed territories. Otherwise, the inner conical body of rat FSCs contains en passant, circumferentially oriented lanceolate endings that are lacking in the cat, whereas the cavernous sinus of the cat has en passant corpuscular endings that are lacking in the rat. Surprisingly, the one type of innervation that is the most similar in both species is a major set of simple, club-like endings, located at the attachment of the ringwulst, that had not previously been recognized as a morphologically unique type of innervation. Although the basic structure of the FSCs is similar in the rat and cat, the numerous differences in innervation suggest that these species would have different tactile capabilities and perceptions possibly related to their different vibrissa-related exploratory behaviors.     

Fluorescent histochemical localization of neutral endopeptidase-24.11 (enkephalinase) in the rat brainstem.

Characterization of the distribution of the peptide-degrading enzyme neutral endopeptidase-24.11 (E.C. 3.4.24.11; NEP; enkephalinase) in the rat brainstem was examined by means of a unique fluorescent histochemical method. Enzyme staining was completely blocked by three potent NEP inhibitors (thiorphan, phosphoramidon, and JHF-26) at a concentration of 50 nM, supporting the specificity of this method to visualize sites of NEP activity selectively. At all levels of the brainstem, NEP was localized to cell bodies, cell processes or terminal-like fields and was localized to more than 90 distinct nuclei or subnuclei. In the mesencephalon these included the central gray, cuneiform n., dorsal and lateral tegmental n., inferior colliculus, interpeduncular n., lateral and medial geniculate n., central linear raphe n., mesencephalic n. of the trigeminal nerve, mammillary nuclei, occulomotor n., red n., superior colliculus, ventral n. of the lateral lemniscus, substantia nigra-ventral tegmental area, and the zona incerta. In the pons, NEP staining was restricted to fewer regions or nuclei, including the dorsal and ventral cochlear n., facial n., motor trigeminal n., principal sensory trigeminal n., parabrachial nuclei, pontine n., the oral and caudal pontine reticular n., pontine olivary nuclei, several pontine tegmental nuclei, pontine raphe nuclei, and the trapezoid n. In the cerebellum, staining was localized largely to the granule cell layer of the cerebellar cortex. Scattered staining was observed in the molecular cell layer. The medulla contained extensive NEP staining localized to nuclei that included the ambiguous n., dorsal motor n. of the vagus, hypoglossal n., inferior olivary n., prepositus hypoglossus n., solitary tract n., nuclei of the spinal tract of the trigeminal n., and the lateral, medial, and superior vestibular nuclei. Nuclei of the medullary reticular formation that were also richly stained for NEP included the raphe magnus n., raphe obscurus n., raphe pallidus n., dorsal, lateral, and ventral reticular nuclei of the medulla, and the gigantocellular, lateral paragigantocellular, linear, paramedian and parvicellular reticular nuclei. The widespread distribution of NEP in the brainstem suggests the existence of a number of functional systems, including the pathways involved in the mechanisms of pain and analgesia, which are potential targets of NEP inhibitors. In most regions, the distribution of NEP closely overlapped with that reported for the enkephalins, and showed a more restricted overlap with the reported distribution of substance P.     

N-methyl- -aspartate-type glutamate receptors are found in post-synaptic targets of adrenergic terminals in the thoracic spinal cord

Adrenergic (C1) neurons in the rostral ventrolateral medulla (RVL) are sympathoexcitatory and project directly to sympathetic preganglionic neurons (SPNs) in the thoracic spinal cord. C1 neurons also contain glutamate which may mediate the excitatory effects of RVL stimulation on SPNs through the N-methyl- -aspartate (NMDA)-type receptor. Dual-labeling immunocytochemistry, combined with electron microscopy, was used to determine if NMDA receptors are located post-synaptic to adrenergic terminals in the spinal cord. Adrenergic terminals were labeled using an antibody directed against phenylethanolamine-N-methyl transferase (PNMT) and the NMDA receptor was identified using an antibody directed against the R1 subunit of the receptor (NMDAR1). NMDAR1 was found primarily in large and small dendrites and a few perikarya. The presence of NMDAR1 in the dendritic targets of PNMT-containing terminals was quantified in spinal cords sectioned either horizontally or coronally. PNMT-labeled terminals formed asymmetric synapses on dendrites containing immunogold labeling for NMDAR1, but NMDAR1 was more often detected in the targets of PNMT terminals when spinal cords were sectioned horizontally (59%) rather than coronally (28%). This difference in prevalence of NMDAR1 in targets of PNMT terminals is likely due to the preferential orientation of SPN dendrites in the horizontal plane, since longer dendritic shafts were visible in horizontal sections. When NMDAR1 was present in the dendritic targets of many adrenergic terminals, it was usually located at sites distal to the adrenergic input. We conclude that NMDA receptor ligands are likely to modulate the activity of dendritic targets of adrenergic terminals in the spinal cord, but are not closely associated with adrenergic synaptic input.     

Cerebral arterial innervation: II. Development of calcitonin-gene-related peptide and norepinephrine in the rat

The pre- and postnatal development of trigeminal calcitonin-gene-related peptide (CGRP)- and sympathetic norepinephrine (NE)-containing nerves supplying the cerebral arteries was studied with immunohistochemistry in rats. At 18-19 days in utero (E 18-19), CGRP fibers were present only as one or two longitudinal bundles zigzagging along the anterior cerebral artery and anterior communicating artery. Growth-cone-like swellings were found at the terminals of individual fibers. In contrast, at this same prenatal age NE fibers were present as a meshwork on all cerebral arteries. The density of NE fibers was higher in the rostral than in the caudal parts of the circle of Willis; growth cones were present on individual fibers at the middle segment of the basilar artery and distal parts of major cerebral arteries. At postnatal day 1-2 (PND 1-2; date of birth = PND 1), the outgrowth of CGRP axons extended along the walls of the middle cerebral and internal carotid arteries. These axons were relatively straight and unbranched. At the same time, NE fibers increased in number and density and continued to form the meshwork pattern on all cerebral arteries. At the end of the first postnatal week, all the longitudinal NE bundles on the rostral part of the circle of Willis began to form circular arborizations. At the end of the second postnatal week, the pattern of NE innervation had completely changed, consisting almost entirely of circumferential rather than tangential fibers. Beginning in the first postnatal week, CGRP fibers increased greatly in number and density and began to form a meshwork pattern. At the second postnatal week, the pattern of CGRP innervation, compared to the pattern at fetal and neonatal stages, had changed significantly, consisting predominantly of a meshwork pattern. By 4 weeks after birth, both the NE and CGRP fiber systems achieved adult densities and patterns. The present results demonstrate the following: 1) Both sympathetic-NE and trigeminal-CGRP innervation of cerebral arteries begin in utero; the NE system innervates corresponding parts of the vessels earlier than the CGRP system. 2) Both NE and CGRP fibers are more dense in the rostral than in the caudal segments of the circle of Willis; this rostrocaudal gradient is expressed in both density and pattern by the earliest fibers of both neurochemical systems and is maintained throughout all developmental stages.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in autonomic control of the cardiovascular system in the Wistar audiogenic rat (WAR) strain

We evaluated autonomic cardiovascular modulation and baroreflex control of heart rate (HR) in a particular epileptic rat strain, Wistar audiogenic rats (WARs). We studied spontaneous baroreflex sensitivity as well as reflex changes in HR evoked by phenylephrine/nitroprusside-induced changes in arterial pressure (AP). Atropine and propranolol were used to measure cardiac autonomic tone. AP and pulse interval (PI) variability analysis were performed in the time and frequency domains (FFT spectral analysis) to evaluate cardiovascular sympatovagal modulation in WARs. AP and HR were higher in WARs (109 ± 2 mm Hg and 366 ± 9 bpm) than in Wistar control rats (101 ± 2 mm Hg and 326 ± 10 bpm). The power of the low-frequency band of both AP and PI spectra, a marker of sympathetic modulation, was higher in WARs than in Wistar control rats. The high-frequency power of the PI spectra in normalized units, which is linked to cardiac vagal modulation, was lower in WARs. Both WARs and Wistar control rats had similar vagal tone (91 ± 13 bpm vs 94 ± 11 bpm, respectively), but sympathetic tone was higher in WARs (30 ± 4 bpm vs 14 ± 4 bpm). No differences were detected in the gain of evoked (1.32 ± 0.1 ms/mm Hg vs 1.35 ± 0.2 ms/mm Hg) or spontaneous (1.34 ± 0.2 ms/mm Hg vs 2.04 ± 0.2 ms/mm Hg) baroreflex sensitivity. The higher AP and HR and the autonomic imbalance (sympathetic predominance) in WARs might be associated with an increased risk of life-threatening cardiovascular events in this strain.     

Effects of the serotonin-uptake inhibitor, fluoxetine, on immunoreactive serotonin innervation in the rat pituitary gland

Serotonin (5-HT)-immunoreactive innervation can be demonstrated in both the pars intermedia and pars nervosa of the rat pituitary gland. Fluoxetine hydrochloride, a 5-HT uptake inhibitor, was administered in single or multiple doses to adult male Sprague-Dawley rats to examine the possibility that 5-HT present in pituitary fibers may be due to uptake of the indoleamine. Paraffin-embedded sections of pituitaries from fluoxetine-treated rats revealed diminution or loss of 5-HT fiber staining in the intermediate, but not in the neural lobe, in all animals examined. Multiple doses of fluoxetine produced the most consistent effects on immunostaining. These observations along with results of our previous studies suggest that the intermediate lobe innervation immunoreactive for 5-HT may be due to uptake of indoleamine from extrinsic sources, while the pars nervosa terminals containing 5-HT most likely originate from 5-HT neuronal perikarya in the lower brainstem or hypothalamus.