Biochemical and morphological effects of testosterone treatment on developing sympathetic neurons

Ontogenetic Change in the Regional Distribution of Dehydroepiandrosterone-Synthesizing Enzyme and the Glucocorticoid Receptor in the Brain of the Spiny Mouse (Acomys cahirinus)

The androgen dehydroepiandrosterone (DHEA) has trophic and anti-glucocorticoid actions on brain growth. The adrenal gland of the spiny mouse (Acomys cahirinus) synthesizes DHEA. The aim of this study was to determine whether the brain of this precocial species is also able to produce DHEA de novo during fetal, neonatal and adult life. The expression of P450c17 and cytochrome b5 (Cytb5), the enzyme and accessory protein responsible for the synthesis of DHEA, was determined in fetal, neonatal and adult brains by immunocytochemistry, and P450c17 bioactivity was determined by the conversion of pregnenolone to DHEA. Homogenates of fetal brain produced significantly more DHEA after 48 h in culture (22.46 ± 2.0 ng/mg tissue) than adult brain homogenates (5.04 ± 2.0 ng/mg tissue; p < 0.0001). P450c17 and Cytb5 were co-expressed in fetal neurons but predominantly in oligodendrocytes and white matter tracts in the adult brain. Because DHEA modulates glucocorticoids actions, the expression of the glucocorticoid receptor (GR) was also determined. In the brainstem, medulla, midbrain, and cerebellum, the predominant GR localization changed from neurons in the fetal brain to oligodendrocytes and white matter tracts in the adult brain. The change of expression of P450c17, Cytb5 and GR proteins with cell type, brain region and developmental age indicates that DHEA is an endogenous neurosteroid in this species that may have important trophic and stress-modifying actions during both prenatal and postnatal life.

Transmitter phenotypic expression in the embryo

The initial appearance and development of noradrenergic and adrenergic phenotypic characters was studied in the rat embryo by immunocytochemical methods. Tyrosine hydroxylase and dopamine-beta-hydroxylase (noradrenergic enzymes) appeared at 11.5 days of gestation (Day E 11.5; 27-30 somites) in sympathetic ganglion primordia and in cells of the gut. While tyrosine hydroxylase and dopamine beta-hydroxylase immunoreactivity increased progressively in ganglion primordia, the enzymes disappeared in the gut cells after E 13.5. However, the gut cells themselves persisted, as indicated by the high-affinity uptake of noradrenaline (norepinephrine). Consequently, initial appearance of noradrenergic characters does not ensure persistence and subsequent development, indicating that early phenotypic expression is a mutable process. This contention was supported by the observations that pharmacological stress of pregnant rats in the form of reserpine, or treatment with glucocorticoids, prolonged the appearance of catecholamines in the gut cells. Thus, maternal-embryonic relations in general, and maternal glucocorticoids in particular, may influence embryonic phenotypic expression. Treatment of embryos with nerve growth factor also prolonged the appearance of noradrenergic characters in the gut cells. Expression of the adrenergic phenotype was apparently regulated differently from noradrenergic expression, since phenylethanolamine-N-methyltransferase (PNMT), the adrenaline-(epinephrine)-synthesizing enzyme, was undetectable in ganglion primordia and gut cells. PNMT initially appeared at E 17.5 in cells which had migrated to be adrenal anlage. Extensive studies suggest that the initial appearance of PNMT occurs independently of glucocorticoid regulation, while subsequent development is dependent on corticoids.

Interactive effects of testosterone and superior cervical ganglionectomy on attraction thresholds to volatile urinary odors in gonadectomized mice

Volatile urinary odors contribute to mate recognition in mice after their detection by the main olfactory epithelium (MOE). We used a habituation/dishabitution task to ask whether the capacity of gonadectomized mice of both sexes to detect and investigate decreasing concentrations of volatile urinary odors from either breeding males or estrous females is modulated by administering androgen or estrogen and if so, whether any effects of these sex steroids are altered by disrupting the sympathetic innervation of the MOE via bilateral superior cervical ganglionectomy (SCGx). In tests given, beginning 51 days after gonadectomy without steroid treatment both male and female subjects detected even the lowest concentrations (1:120 and 1:160 dilutions by volume) of male urinary odors, provided they were SCGx as opposed to sham operated. In subsequent tests given after estradiol benzoate (EB) followed later by 5alpha-dihydrotestosterone (DHT) treatments, neither male nor female subjects detected low concentrations of male urinary odors regardless of whether or not their SCG's were intact. Administration of testosterone (T) prior to a final series of tests restored the ability of gonadectomized subjects of both sexes to detect low concentrations of male urinary odors regardless of their SCG status. This suggests that T, but not its neural metabolites estradiol, or DHT, facilitates responsiveness to low concentrations of male odors in mice of both sexes. In tests given 51 days after gonadectomy without steroid treatment most male and female subjects readily detected the three highest concentrations of estrous female urinary odors whereas SCGx males and females failed to detect the lowest concentrations of these odors. After treatment with EB and then with DHT, gonadectomized mice of both sexes generally failed to detect the three lowest concentrations of estrous female urinary odors regardless of their SCG status. After T treatment; however, subjects of both sexes again detected most dilutions of estrous female urine, provided their SCG's were intact. Again, these results suggest that T, but not estradiol or DHT, facilitates responsiveness to estrous female urinary odors. Provided such an activational effect of T is present, sympathetic, noradrenergic inputs to the MOE may enhance odorant contrast, as previously suggested [Nat. Neurosci. 2 (1999) 106], by reducing the responsiveness of olfactory neurons to low (1:120 and 1:160 dilutions) concentrations of some biologically significant odorants (e.g. male urinary odors) while facilitating their responsiveness to low to moderate (1:80 dilution) concentrations of others (e.g. estrous female urinary odors).

Removal of the superior cervical ganglia fails to block Fos induction in the accessory olfactory system of male mice after exposure to female odors

When exposed to female odors, testosterone-primed male mice show a robust expression of immediate early genes in the vomeronasal organ (VNO) and associated accessory olfactory structures. We asked whether the superior cervical ganglia (SCG), which provide autonomic inputs to the VNO, are required for odor induction of Fos. Gonadally intact male mice received sham, unilateral, or bilateral SCG lesions and were exposed to odors from estrous females. In comparison to clean bedding, female odors significantly increased neuronal Fos immunoreactivity in sites throughout the VNO projection pathway, but these responses were not reliably modified by SCG removal. Thus, noradrenergic inputs to the VNO, which regulate a pumping mechanism thought to facilitate entrance of chemosignals into the VNO lumen, are not required for odors to induce Fos in the mouse accessory olfactory system.

Bulbectomy Enhances Neurogenesis and Cell Turnover of Primary Olfactory Neurons But Does Not Abolish Carnosine Expression

Primary olfactory neurons located in the olfactory neuroepithelium project to the ipsilateral olfactory bulb and undergo a continuous process of neurogenesis and differentiation. We describe, in the adult rat, the kinetics of proliferation, differentiation and survival of primary olfactory neurons either in the presence or absence of their target, the olfactory bulb. The experimental design included unilateral bulbectomy, coupled with a single bromodeoxyuridine pulse 35 days after surgery. The rate of proliferation and survival of olfactory neurons was then examined by immunohistochemistry for bromodeoxyuridine, and the differentiation status by in situ hybridization for calmodulin messenger RNA in immature and mature olfactory neurons and immunohistochemistry for the dipeptide carnosine in mature olfactory neurons. We show that primary olfactory neurons can synthesize carnosine in the absence of the olfactory bulb. However, the number of carnosine-immunopositive neurons in the absence of their target is dramatically reduced to less than one-fourth, whereas the number of olfactory neurons expressing calmodulin messenger RNA is only slightly reduced. The numeric reduction of carnosine-positive neurons in the target-deprived neuroepithelium is correlated with a dramatic reduction in the survival rate of olfactory neurons, since newly generated olfactory neurons are completely lost 35 days after the bromodeoxyuridine pulse. In contrast, in the normal olfactory neuroepithelium almost one-third of newly generated olfactory neurons survive 35 days after the bromodeoxyuridine pulse. On the whole, these data indicate that most of the primary olfactory neurons have a short lifespan but that once they have connected with the olfactory bulb they may persist longer, and suggest that throughout adulthood olfactory neurons are overproduced, differentiate independently from their target, and then undergo a process of target-induced neuronal selection.

Sex difference and steroid modulation of pheromone-induced immediate early genes in the two zones of the mouse accessory olfactory system

Two anatomically and neurochemically distinct zones within the vomeronasal organ (VNO) and accessory olfactory bulb (AOB) have been identified that are responsible for the detection of pheromones. Using markers to distinguish between apical and basal neurons of the VNO neuroepithelium and rostral versus caudal AOB glomeruli, we examined immediate early gene immunoreactivity (IEG-IR) in gonadectomized, steroid-treated mice in response to pheromones of male and female conspecifics. After exposure of estradiol-treated females to soiled male bedding, more VNO neurons in the basal than the apical layer exhibited IEG-IR compared with VNO neurons of estradiol-treated males. Conversely, whereas soiled female bedding failed to induce IEG-IR in VNO neurons of estradiol-treated males or females, both apical and basal neurons were activated in testosterone-treated males. Male and female pheromones also activated mitral and granule cells in the AOBs of all subjects, but responses to different pheromones were distributed across the boundary of the rostral and caudal regions. These data show that differences in the response of males and females to the same pheromonal stimulus are found in the sensory neurons of the VNO. We propose that centrifugal, noradrenergic inputs to VNO neurons, which may differ in the two sexes and respond differently to adult sex steroids, modulate sensitivity to pheromonal stimulation.

Role of thyroid hormones and their receptors in peripheral nerve regeneration

After peripheral nerve injury in adult mammals, reestablishment of functional connections depends on several parameters including neurotrophic factors, the extracellular matrix, and hormones. However, little is known about the contribution of hormones to peripheral nerve regeneration. Thyroid hormones, which are required for the development and maturation of the central nervous system, are also important for the development of peripheral nerves. The action of triiodothyronine (T3) on responsive cells is mediated through nuclear thyroid hormone receptors (TRs) which modulate the expression of specific genes in target cells. Thus, to study the effect of T3, it is first necessary to know whether the target tissues possess TRs. The fact that sciatic nerve cells possess functional TRs suggests that these cells can respond to T3 and, as a consequence, that thyroid hormone may be involved in peripheral nerve regeneration. The silicone nerve guide model provides an excellent system to study the action of local administration of T3. Evidence from such studies demonstrate that animals treated locally with T3 at the level of transection have more complete regeneration of sciatic nerve and better functional recovery. Among the possible regulatory mechanisms by which T3 enhances peripheral nerve regeneration is rapid action on both axotomized neurons and Schwann cells which, in turn, produce a lasting and stimulatory effect on peripheral nerve regeneration. It is probable that T3 up- or down-regulates gene expression of one or more growth factors, extracellular matrix, or cell adhesion molecules, all of which stimulate peripheral nerve regeneration. This could explain the greater effect of T3 on nerve regeneration compared with the effect of any one growth factor or adhesion molecule.

Triiodothyronine exerts a trophic action on rat sensory neuron survival and neurite outgrowth through different pathways

Apart from several growth factors which play a crucial role in the survival and development of the central and peripheral nervous systems, thyroid hormones can affect different processes involved in the differentiation and maturation of neurons. The present study was initiated to determine whether triiodothyronine (T3) affects the survival and neurite outgrowth of primary sensory neurons in vitro. Dorsal root ganglia (DRG) from 19-day-old embryos or newborn rats were plated in explant or dissociated cell cultures. The effect of T3 on neuron survival was tested, either in mixed DRG cell cultures, where neurons grow with non-neuronal cells, or in neuron-enriched cultures where non-neuronal cells were eliminated at the outset. T3, in physiological concentrations, promoted the growth of neurons in mixed DRG cell cultures as well as in neuron-enriched cultures without added nerve growth factor (NGF). Since neuron survival in neuron-enriched cultures cannot be promoted by endogenous neurotrophic factors synthesized by non-neuronal cells, the increased number of surviving neurons was due to a direct trophic action of T3. Another trophic effect was revealed in this study: T3 sustained the neurite outgrowth of sensory neurons in DRG explants. The stimulatory effect of T3 on nerve fibre outgrowth was considerably reduced when non-neuronal cell proliferation was inhibited by the antimitotic agent cytosine arabinoside, and was completely suppressed when the great majority of non-neuronal cells were eliminated in neuron-enriched cultures. These results indicate that the stimulatory effect of T3 on neurite outgrowth is mediated through non-neuronal cells. It is conceivable that T3 up-regulates Schwann cell expression of a neurotrophic factor, which in turn stimulates axon growth of sensory neurons. Together, these results demonstrate that T3 promotes both survival and neurite outgrowth of primary sensory neurons in DRG cell cultures. The trophic actions of T3 on neuron survival and neurite outgrowth operate under two different pathways.

Roles of steroid hormones and their receptors in structural organization in the nervous system

Due to their chemical properties, steroid hormones cross the blood-brain barrier where they have profound effects on neuronal development and reorganization both in invertebrates and vertebrates, including humans mediated through their receptors. Steroids play a crucial role in the organizational actions of cellular differentiation representing sexual dimorphism and apoptosis, and in the activational effects of phenotypic changes in association with structural plasticity. Their sites of action are primarily the genes themselves but some are coupled with membrane-bound receptor/ion channels. The effects of steroid hormones on gene transcription are not direct, and other cellular components interfere with their receptors through cross-talk and convergence of the signaling pathways in neurons. These genomic and non-genomic actions account for the divergent effects of steroid hormones on brain function as well as on their structure. This review looks again at and updates the tremendous advances made in recent decades on the study of the role of steroid (gonadal and adrenal) hormones and their receptors on developmental processes and plastic changes in the nervous system.

Target determination of neurotransmitter phenotype in sympathetic neurons

While the majority of sympathetic neurons are noradrenergic, a minority population are cholinergic. At least one population of cholinergic sympathetic neurons arises during development by a target-dependent conversion from an initial noradrenergic phenotype. Evidence for retrograde specification has been obtained from transplantation studies in which sympathetic neurons that normally express a noradrenergic phenotype throughout life were induced to innervate sweat glands, a target normally innervated by cholinergic sympathetic neurons. This was accomplished by transplanting footpad skin containing sweat gland primordia from early postnatal donor rats to the hairy skin region of host rats. The sympathetic neurons innervating the novel target decreased their expression of noradrenergic traits and developed choline acetyltransferase (ChAT) activity. In addition, many sweat gland-associated fibers acquired acetylcholinesterase (AChE) staining and VIP immunoreactivity. These studies indicate that sympathetic neurons in vivo alter their neurotransmitter phenotype in response to novel environmental signals and that sweat glands play a critical role in the cholinergic and peptidergic differentiation of the sympathetic neurons that innervate them. The sweat gland-derived cholinergic differentiation factor is distinct from leukemia inhibitory factor and ciliary neurotrophic factor, two well-characterized cytokines that alter the neurotransmitter properties of cultured sympathetic neurons in a similar fashion. Recent studies indicate that anterograde signalling is also important for the establishment of functional synapses in this system. We have found that the production of cholinergic differentiation activity by sweat glands requires sympathetic innervation, and the acquisition and maintenance of secretory competence by sweat glands depends upon functional cholinergic innervation.

Post-natal development modulates the rat seminal vesicle sensitivity to sympathomimetic agonists

The post-natal development-related changes in the sensitivity to sympathomimetic agonists were studied in the seminal vesicle of 40-, 60- and 120-day old rats by determining the pD2 values for adrenaline, phenylephrine and methoxamine. The age-related changes in the neuronal and extraneuronal uptake of sympathomimetic agonists were also determined. The seminal vesicle sensitivity to adrenaline, phenylephrine and methoxamine increased in sexually mature rats (60- and 120-day old) (concentration-effect curves shifted to the left and pD2 values increased) when compared with immature rats (40-day old). Cocaine, a neuronal uptake inhibitor, induced supersensitivity to adrenaline at all ages, but did not affect the sensitivity to methoxamine. The ratio between the EC50 values for adrenaline in the presence and in the absence of cocaine was reduced in tissues of mature animals. This reduction suggests a loss of function of the neuronal uptake system with sexual development. In the presence of cocaine the pD2 value for adrenaline was increased during sexual development. Thus, the age-related changes in the adrenaline sensitivity were observed even when neuronal uptake was not operative, suggesting age-related changes at the post-junctional level, which was confirmed by the increase in the seminal vesicle sensitivity to methoxamine. In the presence of the extraneuronal uptake inhibitor, corticosterone, the sensitivity to adrenaline did not change and the age-related changes persisted.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular aspects of the regulation of tyrosine hydroxylase by testosterone

Previous studies have demonstrated that the sympathetic hypogastric ganglia (HG) are dependent upon the continued presence of testosterone for normal development and maintenance of tyrosine hydroxylase (TH) activity. The regulation of TH by testosterone has been examined further to determine whether the reduction in TH activity following castration is associated with changes in levels of TH protein and mRNA. TH protein was measured by immunotitration of HG homogenates using a TH-specific antibody, and TH-specific mRNA was detected by hybridization of dot blots of total RNA isolated from HG with a cDNA probe coding for TH. The results show that tyrosine hydroxylase activity, protein and mRNA are coordinately reduced in a graded fashion at 1, 2 and 4 weeks following castration. Testosterone replacement therapy immediately following castration prevents the decrease in TH levels. The results indicate that gonadal steroids regulate the biosynthesis of TH in the HG. Testosterone may control TH either directly by interacting with neurons of the HG, or indirectly by altering levels of trophic factors in the target tissues.

Castration reduces the nocturnal rise of pineal melatonin levels in the male rat by impairing its noradrenergic input

Abstract The effects of castration and testosterone treatment on pineal day-night rhythms were studied in male rats. Bilateral gonadectomy was performed at 21 days of age. Testosterone propionate was given subcutaneously to castrated animals in a dose of 10 mug/100 g body weight during two consecutive days before sacrifice. Animals were killed 40 days after gonadectomy at four different times of a 12:12 h light-dark cycle (1600, 2400, 0400 and 0800h). Tyrosine hydroxylase activity was measured in individual pineals by means of high-performance liquid chromatography determination of L-DOPA formed. Pineal levels of norepinephrine, dopamine, 5-hydroxytryptamine and 5-hydroxyindole acetic acid were determined by high-performance liquid chromatography with amperometric detection, while pineal melatonin content was measured by radioimmunoassay. Castration abolished the day-night rhythms of pineal tyrosine hydroxylase activity and norepinephrine content, both by elevating their daytime levels and by blocking their nocturnal rise. In addition, gonadectomy drastically modified pineal indoleamine metabolism by increasing daytime levels of both 5-hydroxytryptamine and 5-hydroxyindole acetic acid, and by reducing the nocturnal elevation of pineal melatonin content. Testosterone treatment was unable to prevent the effect of orchidectomy on pineal rhythms of tyrosine hydroxylase activity, 5-hydroxytryptamine or 5-hydroxyindole acetic acid content, however it partially restored the day-night pineal rhythms of both norepinephrine and melatonin content. These results are indicative of a possible participation of reproductive hormones in the control of pineal rhythmic activity in the male rat. Apparently, since gonadectomy abolished the nocturnal rise of both pineal tyrosine hydroxylase activity and norepinephrine content, the primary site of action of reproductive hormones could be at the level of the superior cervical ganglion.

Acquisition of cholinergic and peptidergic properties by sympathetic innervation of rat sweat glands requires interaction with normal target

The sweat glands, a target of cholinergic sympathetic neurons, were replaced with parotid gland, a target of noradrenergic sympathetic neurons, in neonatal rats. This transplantation paradigm allowed sympathetic neurons that would normally innervate the sweat glands and develop a cholinergic phenotype to innervate the parotid gland instead. The innervation of the transplanted parotid gland did not develop a cholinergic phenotype, as assessed by choline acetyltransferase activity and acetylcholinesterase immunoreactivity, but continued to express intense catecholamine fluorescence. In addition, immunoreactivity for vasoactive intestinal peptide, normally expressed by the sympathetic innervation of the sweat glands but not the parotid, was observed in only a small percentage of the parotid-associated fibers. These results suggest that cellular interactions between neurons and their targets play an important role in the differentiation of mature neurotransmitter and neuropeptide phenotypes in vivo.

Sympathetic sprouting into neonatally denervated contralateral target: superior cervical ganglion neuronal numbers and sizes

Unilateral superior cervical ganglionectomy results in establishment of an atypical functional projection from the contralateral ganglion to the denervated superior tarsal muscle in neonatal but not in juvenile or adult rats. Previous studies of peripheral nervous system development have attributed enhanced neuroplasticity to either formation of pathways by surplus cells rescued from cell death (hypothanasia-induced hyperplasia), or more vigorous terminal aborization of neurons innervating adjacent target zones (collateral sprouting with associated somatic hypertrophy). In the present study, experiments were performed to determine if neonatal sympathetic sprouting to contralaterally denervated target is associated with superior cervical ganglion neuronal hyperplasia or hypertrophy. Fluoro-Gold injections of right superior tarsal muscle in adult rats following neonatal ganglionectomies labelled cells in the contralateral superior cervical ganglion, whereas cells were labelled strictly ipsilaterally in sham operates. Profile areas of contralaterally projecting neuronal somata were twice as large as those providing ipsilateral innervation. Ganglion volumes, neuronal nuclear diameters and packing densities, and total neuronal numbers in left superior cervical ganglia of animals receiving neonatal right superior cervical ganglionectomy were comparable to those of both right and left ganglia of sham-operated controls. It is concluded that establishment of a contralateral projection does not rescue significant numbers of neurons from naturally occurring cell death. Rather, contralateral sprouting derives from neurons showing pronounced somatic hypertrophy.

The impact of sexual dimorphism on neuron numbers in the superior cervical ganglion of the rat

Other workers have reported a sexual dimorphism in the number of neurons that project from the rat superior cervical ganglion (SCG) via the internal carotid nerve (ICN). We have re-examined this situation by comparing ganglionic neuron numbers as well as the number of neurons labelled retrogradely from the iris and the pineal gland, in age-matched adult male and female rats. No significant dimorphism was seen in total cell numbers or in the cell populations supplying iris or pineal gland, although there was a trend towards more neurons in male animals. From evaluation of our results and the published data, we suggest that the variation in absolute numbers of neurons counted in the SCG is so wide, within genders, that any impact of gender differences on cell numbers is of little significance.

Polyamines induce precocious development in rats. Possible interaction with growth factors

The study reports the effects of daily subcutaneous injections of the biogenic polyamines putrescine, spermidine and spermine (10 mg/kg each) given for a short postnatal period, on growth and development of rats. Polyamine treatment, while only slightly enhancing normal body weight gain, prevented the weight loss caused by surgical injury of 5-day-old animals. The treatment resulted in earlier eyelid and ear opening and in earlier maturation of righting and gripping responses. Increased number of neurons in the superior cervical ganglion that is caused by polyamine treatment, could not be prevented by castration of newborn rats, thus excluding the testes as a site through which polyamines may exert their action. An apparent increase in immunohistochemically detectable nerve growth factor was evident in iris and submaxillary salivary gland of polyamine-treated animals, but no change in epidermal growth factor immunohistochemistry was detected in the salivary gland. We conclude: (1) treatment of newborn rats with polyamines can accelerate somatic and neurobehavioral development; (2) further studies are required in order to verify and quantitate the effects of polyamines on growth factors, and (3) the results imply that exogenous polyamines may exert their growth-promoting effects on a number of cell types when these cells experience periods of polyamine dependence.

Steroid hormones and neurotrophism: relationship to nerve injury

Current data on the neurotrophic effects of steroid hormones suggest that, in brain and spinal cord regions containing receptor systems, steroids act at the level of RNA and protein synthesis to effect metabolic changes associated with nerve-cell survival, elaboration/maintenance of dendritic and axonal processes, synaptogenesis, and neurotransmission. While many of these effects appear to be associated with the neuroanatomical systems involved in the endocrine and behavioral aspects of reproduction, evidence does exist for similar neurotrophic effects outside the reproductive sphere. Both estrogens and androgens appear to exert this stimulatory, growthlike effect on target neurons. The effects of progesterone are not discussed in this review because relatively little information is available regarding the independent effects of progesterone on the brain. We have just completed a study (Jones et al., 1987b) which suggests that progesterone may act independently in the brain to affect protein synthesis. A number of conclusions concerning the mechanism of steroid action in producing trophic effects on neurons can be drawn. First, the time course of hormone action is similar to that found in nonneural target tissue, such as the uterus. Second, steroid hormones act on neurons through receptor-mediated genomic activation. Third, this effect on the genome appears to be at the level of both transcription and translation. Fourth, there is brain-region specificity in the gene products resulting from steroid hormone administration. Finally, short-term exposure to estrogens or androgens generally results in an anabolic response within target neurons. The brain and spinal cord, injured either by disease or by experimentally induced trauma, is responsive in a reparative manner to exogenous and/or endogenous gonadal steroid hormones. The mechanism underlying this therapeutic role of steroids on damaged neurons is not known but has been postulated to involve direct action of steroid hormones or target neurons. It has been hypothesized that two diseases, Alzheimer's and ALS, may be related to steroid hormone/receptor deficiencies. In this regard, Appel (1981) has suggested that putative "neurotrophic hormones" acting at the synapse may be critical in maintaining the neural networks affected in ALS, Alzheimer's disease, and parkinsonism. Extending that hypothesis to include direct action of such putative hormones within the cell body and at the level of the genome, the evidence presented in this discussion would argue that possible candidates could be gonadal steroids.(ABSTRACT TRUNCATED AT 400 WORDS)

Early polyamine treatment enhances survival of sympathetic neurons after postnatal axonal injury or immunosympathectomy

We have recently demonstrated that following injury of their axon, sympathetic neurons of the rat superior cervical ganglion become dependent on polyamine synthesis for their survival. In addition we have observed that the treatment of newborn rats with biogenic polyamines can prevent the naturally occurring reduction in the number of neurons in the ganglion. In the present study groups of newborn rats were subjected to either postganglionic nerve crush (axotomy) or to treatment with antiserum to nerve growth factor (immunosympathectomy), two treatments which result in a massive loss of neurons in the ganglion. Daily injections of the polyamines putrescine, spermidine and spermine (10 mg/kg each), for 7 days after the operation to the axotomized group, and for 9 days starting with the first antiserum injection to the immunosympathectomized group, attenuated the nerve cell loss. The polyamine treatment also attenuated the reduction in the activity of the neurotransmitter-synthesizing enzyme tyrosine hydroxylase observed after both axotomy and immunosympathectomy in the ganglion. These results further indicate that polyamines are important for the survival of sympathetic neurons and, while their mechanism of action is unknown, an interaction with nerve growth factor regulation cannot be excluded. In the iris, the reduction observed in [3H]norepinephrine uptake after the two noxious treatments was unproportionately small when compared to the large drop in the number of parent neurons in the ganglion. This suggests that compensatory mechanisms exist which act to adjust the number of functional axon terminals per neuron so that the number of terminals innervating the target remains relatively constant.

Biochemical and morphological effects of castration on the postorganizational development of the hypogastric ganglion

The biochemical and morphological development of the sympathetic hypogastric ganglion (HG) was examined subsequent to postnatal castration at 10-11 days of age. Previous studies suggested that tyrosine hydroxylase (T-OH) activity, an index of noradrenergic maturation, and choline acetyltransferase (ChAT) activity, a marker for preganglionic terminal formation, were dependent on gonadal hormones during normal ontogeny. In the present studies, morphometric analyses of the HG revealed that the cross-sectional area of the cell soma and nucleus were significantly reduced following postnatal castration at day 10. Conversely, castration produced no change in the number of HG neurons. In addition, postnatal castration prevents the development of postsynaptic T-OH activity to a greater extent than ganglionic protein resulting in a significant loss of T-OH specific activity. In contrast, presynaptic ChAT activity was reduced in parallel with ganglionic protein, thus ChAT specific activity was unchanged. Testosterone replacement therapy, even in groups where treatment was delayed for up to 2 weeks after castration, completely reversed deficits in both T-OH and ChAT activities. These studies suggest that altered development of ganglion protein subsequent to postnatal castration is related to decreases in the size of neurons and not to the loss of neurons. The lack of cell loss also suggest that decreased levels of postsynaptic T-OH activity results from a loss of enzyme activity per cell and the decreased levels of ChAT activity probably represent fewer presynaptic terminals per neuron. In addition, delayed testosterone replacement subsequent to castration was effective in restoring enzyme activities suggesting an 'activational' not 'organizational' role for testosterone after postnatal day 10.

Effects of gonadal steroids on nerve growth factor receptors in sympathetic and sensory ganglia of neonatal rats

The numbers of neurons in the rat superior cervical sympathetic ganglion (SCG) differ in males and females, with the males having 30% more SCG neurons than females at 60 days of age. This sex difference arises during the early postnatal period, when testosterone administration increases the numbers of neurons and alters the nerve growth factor (NGF) content of the rat SCG. In contrast, there is no gender difference in number of neurons in the L1 dorsal root ganglion. In both males and females, the amount of NGF bound per ganglion increased between postnatal days 5 and 15 (P5 and P15) in both dorsal root ganglia (DRGs) and the SCG. There is also a gender difference in NGF binding: SCGs and DRGs of female rats at both P5 and P15 bind more NGF per ganglion than do those of males. This effect was more marked in DRGs than in the SCG. Treatment of neonatal females with testosterone reduced NGF binding in both SCGs and DRGs to levels comparable to males at P5, and in DRGs at P15. In contrast, treatment of males with testosterone from birth resulted in a 2-3 fold increase of NGF binding in both SCGs and DRGs as compared to controls at P15. At P15, testosterone treatment of females increased NGF binding in the SCG. Males and females had opposing responses to neonatal exposure to estradiol. Treatment with estradiol from birth increased NGF binding in SCGs and DRGs of females, but had no effect on NGF binding of SCGs, and reduced NGF binding in DRGs of males.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of the sex difference in neuron numbers of the superior cervical ganglion: effects of transection of the cervical sympathetic trunk

The number of superior cervical ganglion (SCG) neurons does not differ for males and females on the day of birth, but by 15 days, after most of the normal neuron death has occurred, males have significantly more neurons than females. This difference persists in the adult. The present study was undertaken to determine whether the presence of afferent input to the SCG is required for the development of this sex difference. Bilateral transection of the cervical sympathetic trunk, which deafferents the SCG neurons, or a sham operation was performed on male and female Sprague Dawley rats on the day of birth. Numbers of neurons were counted in SCGs of animals sacrificed on either postnatal day 4 or 15, before or after normal development of the SCG sex difference. At 4 days, the number of SCG neurons in sham-operated males and females were not different, but by 15 days, females had lost a significant number of neurons, whereas the males had not. Transection of the cervical sympathetic trunk led to a significant loss of over 6,000 SCG neurons by postnatal day 4 in both males and females. Whereas some of this loss is due to axotomy of caudally projecting SCG neurons, at least half of the neuron loss is due to removal of the afferent input. At 15 days, sham-operated males had significantly more SCG neurons than did sham-operated females, but the gender difference was not significant in animals with neonatally deafferented ganglia. Thus, the normal development of the gender difference in SCG neuron numbers requires an intact afferent input.

Altered sympathetic-salivary gland development: delayed response to postnatal castration

These studies defined the normal and hormonally altered development of activity for tyrosine hydroxylase (T-OH), the rate-limiting enzyme in catecholamine biosynthesis (Levitt et al., 1965), and choline acetyltransferase activity (CAT) in the male rat superior cervical ganglion (SCG). Additionally, salivary gland weight was monitored. Two distinct developmental plateaus for postsynaptic T-OH activity exist. The first plateau represents the prepubertal level, which is significantly lower than the second postpubertal plateau. In contrast, presynaptic CAT activity displayed only a single plateau, commencing at approximately 45 days of age. The effects of postnatal castration (at 10 or 11 days of age) on the submandibular gland and T-OH activity were delayed until after puberty. No change in T-OH activity was seen at two and four post-operative weeks between control and castrated animals; however, T-OH activity was significantly less in castrated animals at 12 and 16 post-operative weeks. Testosterone replacement reversed the effect of castration on T-OH activity. Conversely, CAT activity in the SCG was unchanged by postnatal castration for at least 16 post-operative weeks, the longest time point studied. The failure of castrated animals to display the normal developmental increase in T-OH activity following puberty was comparable with the effect of castration on the development of submandibular salivary gland weight. These results suggest that in postpubertal male rats, development of T-OH activity in the superior cervical ganglion is influenced by testosterone. The parallel effects of castration on submandibular gland weight imply that testosterone regulates T-OH activity via an indirect mechanism. In contrast to noradrenergic enzyme activity and target tissue size, the ontogeny of presynaptic CAT activity appears to be insensitive to testosterone levels.

Sex differences in nerve growth factor levels in superior cervical ganglia and pineals

The current studies were undertaken to determine whether males or neonatally testosterone-treated rats of either gender have elevated endogenous levels of NGF in the SCG and one of its targets, the pineal gland. The ages studied were 5 days postnatal, which is at the peak of normal neuron death in the SCG but before a significant gender difference is present; 15 days, when normal neuron death is largely complete and males have more SCG neurons than females; and 30 days, when target innervation has matured. At 5 days, while neuron death is occurring, but before there is a significant gender difference in neuron number in the SCG, pineal glands and SCGs of males had higher NGF content than those of females. The increased NGF in the ganglia of males at the time that these neurons are undergoing neuron death may play a role in the development of the sex difference in SCG neuron numbers. At 15 days, females had more NGF in their pineal glands and SCGs than did males, even though males have significantly more SCG neurons at this age than do females. This gender difference in the developmental course of NGF content could promote the survival of different populations of neurons in males and females. By 30 days, SCG and pineal NGF content of males was almost twice that of females. This is consistent with the presence of more neurons in the SCGs of males at this age. Both the pineal gland and the SCG showed a loss of approximately 80% content of NGF during the first postnatal month(ABSTRACT TRUNCATED AT 250 WORDS)

The role of neuron death in the development of the gender difference in the number of neurons in the rat superior cervical ganglion

Adult male rats have more neurons in their superior cervical ganglia than do adult females. This difference arises over the first two postnatal weeks, and is apparently related to perinatal levels of circulating testosterone. Exposure of neonatal rats to testosterone or estradiol during the first postnatal weeks results in an increase in the number of neurons in the superior cervical ganglion seen at 15, 30 or 60 days postnatally. The present studies were undertaken to determine whether this observed increase in neurons is due to an increase in neuronal proliferation or to a decrease in neuronal death. Results of autoradiographic studies show no evidence of enhanced neuronal proliferation following postnatal exposure to estradiol, but do show an increased survival of a prenatally labeled population of cells. Counts of degenerating cells in the superior cervical ganglion show that during the peak period of normal neuronal degeneration, on postnatal day 5, 17-beta-estradiol or testosterone propionate treated animals have significantly fewer degenerating superior cervical ganglion cells than do vehicle-injected littermate controls. In addition, vehicle-injected females have more degenerating cells on day 5 than do vehicle-injected males. Taken together these results provide strong evidence that the increase in superior cervical ganglion neurons seen after neonatal exposure to estradiol results from a reduction in developmental neuron death.

Testosterone application influences sympathetic activity of intracardiac nerves in non-trained and trained mice

Application of testosterone and/or physical exercise causes degenerative and then regenerative patterns of intracardiac sympathetic neurons. Observations in 3 stages (1, 3 and 6 weeks) illustrate the adaptative changes of sympathetic neurons as a response to these stimuli and show that the effects following testosterone application or physical exercise are comparable. Ultrastructural investigations indicate that the sympathetic neurons are more sensitive to testosterone than to physical exercise. The combination of testosterone plus training indicates overlapping effects of these two stimuli. The system of adrenergic nerve fibers seems to be overstimulated. Its reaction pattern is found not only to depend on time but also on the intensity of the stimuli.

Gonadal hormone regulation of neurotransmitter synthesizing enzymes in the developing hypogastric ganglion

The effects of postnatal castration at 10-11 days of age were examined in the sympathetic hypogastric ganglion (HG). Assays for choline acetyltransferase (ChAT) activity, a biochemical marker for presynaptic cholinergic maturation, and the activity of tyrosine hydroxylase (T-OH), the rate limiting enzyme in postsynaptic catecholamine biosynthesis and an index of noradrenergic development, were employed to monitor HG ontogeny. After 1 postoperative week ChAT activity and T-OH activity were significantly reduced in castrated animals as compared to sham operated controls. Over the 12 week postoperative observation period T-OH activity never varied significantly from the day 10 precastration value; thus, by 12 postoperative weeks T-OH activity in the castrated animals was 3% of the control value. In contrast, ChAT activity and total ganglion protein continued to mature in the castrated animals, but at diminished rates, so that by 12 postoperative weeks both indices were approximately 40% of the control values. Testosterone replacement therapy restored both ChAT and T-OH activities to control levels. Additionally, testosterone replacement restored the control level of activity for DOPA decarboxylase, a catecholamine synthetic enzyme which is differentially regulated from T-OH. The failure of enzyme activities to develop normally subsequent to castration on postnatal day 10 suggests that testosterone regulates the postorganizational maturation of postsynaptic noradrenergic enzyme activities and presynaptic ChAT activity.

Estrogen treatment enhances survival of cultured fetal rat amygdala neurons in a defined medium

Effects of estradiol on the survival of cultured fetal rat amygdala neurons were estimated to assess a possible organizational action of the sex steroid on the developing amygdala tissue. Dissociated 17-day fetal amygdala cells were cultivated initially in a serum-containing and then in a serum-free defined medium. The survival of the cells in the serum-free medium was highly enhanced when supplemented with estradiol at the concentration of 10 ng/ml. Predominant cell populations of the culture were identified as neuronal cells by the tetanus toxin labeling method. The results support the idea that sex steroids play a role in the brain sexual differentiation by enhancing the neuronal survival in the developing amygdala tissue.

Effects of neonatal castration or treatment with dihydrotestosterone on numbers of neurons in the rat superior cervical sympathetic ganglion

There is a normal sexual dimorphism in the number of neurons in the rat superior cervical sympathetic ganglion (SCG), with adult males having more neurons in this ganglion than females. We confirm this finding here, report that this sex difference is not present at birth and that neonatal castration of males reduces the adult sex difference. These results indicate that perinatal levels of circulating testicular hormones play a role in regulating the numbers of neurons in the SCG. Treatment of neonatal rats with testosterone propionate or estradiol significantly increases the number of neurons in the SCG. To determine whether this effect is primary androgenic or estrogenic, the effects of dihydrotestosterone, on SCG neuron number were investigated. Dihydrotestosterone, unlike testosterone, is not aromatized to estradiol intracellularly. There was no difference in the number of neurons between animals injected from birth with vehicle or dihydrotestosterone. This difference in effects between dihydrotestosterone and testosterone suggests that the actions of testosterone may be via aromatization to estradiol, rather than action at an androgen receptor.

Neurochemical changes in murine trisomy 16: delay in cholinergic and catecholaminergic systems

Two strains of Mus musculus musculus, C57BL/6J and CD-1, and Mus musculus poschiavinus, the tobacco mouse, were used to study the effects of increased gene dosage of mouse chromosome 16 (MMU 16). A developmental delay has been found in the brains of murine trisomy 16 (Ts16) fetuses. Both the brain weight (in all three strains) and DNA content (in CD-1) were reduced, while protein content was unchanged in Ts16 compared to normal littermates. The daily increments of weight and protein (except in M. m. poschiavinus) were significantly greater in Ts16. The activities of choline acetyltransferase and acetylcholinesterase and muscarinic receptor binding were reduced. Their daily increments were also reduced to less than 56% that of littermates in Ts16 brains. The rate limiting enzymes of catecholaminergic neurons, tyrosine hydroxylase and dopamine beta-hydroxylase, and the concentration of catecholamines in the brains of Ts16 animals were lower. The activities of three other catecholaminergic enzymes, DOPA decarboxylase, catechol O-methyltransferase, and monoamine oxidase, were generally elevated in Ts16 brain, as were their daily increments. These observations indicate a significant developmental alteration in the maturation of the trisomic brain and suggest future avenues for defining the effect of increased gene dosage of MMU 16 in the CNS.

Hormonal regulation of adult sympathetic neurons: the effects of castration on tyrosine hydroxylase activity

The effects of the hormone testosterone on neurotransmitter synthesis in peripheral sympathetic ganglia were examined in adult male Sprague-Dawley rats. Tyrosine hydroxylase (T-OH), the rate limiting enzyme in catecholamine biosynthesis was examined in the hypogastric (HG), coeliac (CG), and superior cervical ganglion (SCG) subsequent to castration. Initial studies indicated that 2 weeks after surgery, HG T-OH activity fell to approximately 30% of control. In order to more clearly define the pattern of testosterone effects, HG was examined 1, 2 and 4 weeks after surgery. T-OH activity was 67%, 50% and 11% of control at these 3 respective time points, and the observed alteration in T-OH activity appeared to parallel changes in the size of pelvic target organs. Similar hormonal effects did not occur in other peripheral sympathetic ganglia; T-OH activity was unchanged in SCG and CG when examined 1 month after castration. Enzyme activity was restored following replacement therapy with testosterone, whereas the neural metabolite 17-beta estradiol was without effect. The recovery in T-OH activity was associated with partial recovery of target organ size. These studies suggest that hormonal factors regulate neurotransmitter synthesizing enzymes in adult sympathetic neurons and may do so via consequences of alterations in target organs. These observations parallel similar events in the developing nervous system.

Target organ regulation of substance P in sympathetic neurons in culture

Target organ regulation of the putative, peptide neurotransmitter, substance P (SP) was examined in explants and dissociated cell cultures of the neonatal rat sympathetic superior cervical ganglion (SCG). SP levels increased dramatically in explants, rising more than 30-fold after 72 hr in culture. By contrast, peptide levels did not increase in dissociated ganglion cultures. However, SP increased almost 10-fold in cell cultures grown on a monolayer of cells derived from the pineal or salivary gland, targets of the SCG. By contrast, SP content did not increase in cultures grown on a substrate of cells derived from heart or intestine. Peptide identity in the SCG-target cocultures was authenticated by means of combined high-pressure liquid chromatography (HPLC)-radioimmunoassay. Moreover, immunohistochemical examination localized the peptide virtually exclusively to sympathetic neurons and nerve processes. Mechanisms mediating the sympathetic-target interaction were examined in SCG-pineal cocultures. The increase in peptide required interactions with living tissue, since substrates of killed target cells did not elevate SP levels. The target influences were not mediated by nerve growth factor or indoleamines, potential secretory products of pineal in culture. Veratridine treatment prevented the increase in SP in the cocultures, and tetrodotoxin blocked the veratridine effect, suggesting that sodium influx and membrane depolarization prevent SP elevation. Our observations suggest that sympathetic neuron interactions with target organs influence peptidergic expression, and that this interaction may be restricted to certain appropriate target structures.

Hormonal regulation of sympathetic neuron development. The effects of neonatal castration

The effects of neonatal castration on neuronal ontogeny were examined in peripheral sympathetic ganglia in male Sprague-Dawley rats. Tyrosine hydroxylase (T-OH) activity, the rate-limiting enzyme in catecholamine biosynthesis and a marker of noradrenergic maturation, was examined in the hypogastric (HG) and superior cervical ganglion (SCG). Initial studies characterized the normal development of T-OH activity in HG ganglia. Neonatal castration at 10-11 days of age prevented the normal ontogeny of HG T-OH activity: T-OH activity failed to develop normally and was 17% of sham-operated littermate controls when examined at 8 weeks of age, and less than 5% when studied 10 weeks after surgery. In contrast to the effects in HG, there was no change in enzyme activity in the SCG. Replacement therapy with testosterone decanoate completely reversed the developmental alteration in enzyme activity. These observations suggest that hormonal factors modulate noradrenergic ontogeny in peripheral sympathetic ganglia but these effects appear restricted to ganglia whose targets include hormonally dependent sex organs.

Prenatal exposure of male mice to androgen increases neuron number in the hypogastric ganglion

There is a sexual dimorphism in the hypogastric ganglion innervating the internal genitalia of mice. We now report that prenatal exposure of male mice to testosterone propionate brings about a significant increase of neuronal number in the hypogastric ganglion. This suggests that sexually dimorphic nature of the hypograstric ganglion depends on the prenatal hormone environment.

Neuron numbers in the superior cervical sympathetic ganglion of the rat: a critical comparison of methods for cell counting

Published values for the number of neurons in the superior cervical ganglion of the adult rat range from 13 000 to 45 000. These studies have employed different methods for determining what unit to count (cell body, nucleus, nucleolus), how many sections to count, and how to correct the raw counts for split particles and for profiles that are too small to resolve. The purpose of this study was to examine the extent to which these parameters may influence the calculated value for the total number of neurons, using computer simulations of neuron populations. These simulations permitted us to determine the effects on neuron number of varying the diameter of the neuronal nucleus, the size of the smallest resolvable profile, and the thickness of the section. The data from the simulations were used to test the validity of several methods that are in common use for correction of neuron counts. Our results indicate that most of the methods that are in routine use are unsatisfactory. We propose the use of either one of two methods that consistently result in highly accurate estimates of neuron numbers. These are: (1) a modification of the method proposed by Hendry (1976), using computer analysis; or (2) a modification of the method proposed by Abercrombie (1946), which does not require the use of a computer.

Neonatal testosterone treatment increases neuron and synapse numbers in male rat superior cervical ganglion

Neonatal treatment with gonadal steroids has been reported to alter morphological as well as functional development in various regions of the brain and spinal cord. Among the observed alterations are changes in numbers of neurons and in the organization and numbers of synapses. These regions have been found to be sexually dimorphic, and the dimorphism dependent upon gender differences in circulating levels of gonadal steroids. Neonatal treatment with testosterone has been shown to produce an increase in the number of neurons in the superior cervical sympathetic ganglion in female rats. The present studies were designed to investigate the possibility of a normally occurring sexual dimorphism in the SCG of the rat, and to characterize the effect of neonatal treatment with testosterone on neurons and synapses in the male rat. We report a sexual dimorphism in the number of neurons but not in the number of preganglionic axons or ganglionic synapses. In addition, neonatal administration of testosterone propionate results in a 40% increase in the number of superior cervical ganglion neurons in treated male rats over the control male number at 15 and 30 days of age. The testosterone propionate treatment results in a 66% increase in the number of synapses in male superior cervical ganglia, without a concomitant increase in the number of preganglionic axons.

Molecular mechanisms of neuroendocrine integration in the central nervous system: an approach through the study of the pineal gland and its innervating sympathetic pathway

In the brain specialized cells known as 'neuroendocrine transducers' translate an input of neural activity into a hormonal output, e.g. oxytocin released into the blood stream. Other, more typical neurons make the reverse conversion constituting chemoreceptors which transform the hormonal 'language' into changes in their firing rate ('endocrine-neural' transduction). 'Endocrine-endocrine' transducing events occur at the level of the neurosecretory cells that translate a hormonal signal into another, different, hormone output. This article reviews the molecular aspects of several neuroendocrine integrative processes in the hypothalamus, the pineal gland and the cervical sympathetic pathway. The discussed results indicate that the pineal gland and its innervating sympathetic neurons located in the superior cervical ganglia constitute an easy-to-manipulate model system for the study of basic neuroendocrine mechanisms because: (i) receptors for various hormones exist in the mammalian pineal and sympathetic ganglia; (ii) the pattern of pineal steroid metabolism resembles that of the neuroendocrine hypothalamus; (iii) pineal estrophilic and androphilic receptors as well as the pattern of steroid metabolism are modulated by the sympathetic nerves; (iv) neuronal activity in the cervical sympathetic pathway is modified by hormone treatment at preganglionic, ganglionic and postganglionic sites.

Sex-differences in catecholamine metabolites in human urine during development and at adulthood

Adrenergic amines (dopamine [DA], norepinephrine [NE], epinephrine [E] and related compounds (DOPA, 3-methoxytyramine [MT], normetanephrine [NMN], metanephrine [MN], 3-5-dihydroxyphenylacetic acid [DOPAC], vanilmandelic acid [VMA] were analyzed in urine of human from one day to 40 years of age, in view to investigate the sex influence on catecholamine metabolism during life. In neonatal life (1 day to 3.5 months), the total amounts of urinary (E + MN) and (NE + NMN + VMA) were lower in girls than in boys, the former two compounds being mainly of adrenal medullary origin and the latter three coming largely from the sympathetic neurons. In adulthood, women excreted epinephrine (12.5 +/- 2.2 micrograms/24 hours) at lower levels then men (22.8 +/- 4.5 micrograms/24 hours) but no sex related differences occurred in the total amounts of urinary E + MN and NE + NMN + VMA. It is concluded from our study that, during the neonatal life, girls exhibit a lesser adreno-sympathetic maturity than boys, but full maturation of peripheral adrenergic sites is reached near to the fifth year of age in both sexes. The role of testosterone has been discussed. In adults, the lower epinephrine levels found in women urine do not seem to result from a sex difference in the degree of adrenergic maturity, but perhaps partly from an increased rate of epinephrine inactivation by catechol-O-methyltransferase.

Hormonal regulation of axonal sprouting in the hippocampus

Removal of septal fibers to the rat hippocampal formation is followed by an ingrowth of sympathetic axons into the deafferented regions. We have shown previously that the pattern of sprouting is more restricted in males than in females when the lesions are made in mature animals, but is almost the same if lesions are made during the early postnatal period. In the present study, the relationship of circulating sex hormones to the sprouting response was investigated by comparing the extent of sympathetic axon ingrowth following fimbrial lesions in intact or gonadectomized adult male and female rats. The effects of manipulating sex steroids during development was examined by comparing sympathetic axonal sprouting after fimbrial lesions in rats which were castrated (male) or treated with testosterone (females and castrated males) on postnatal day 2. We find that (1) gonadectomy of either adult female or male rats does not affect the sprouting response, but (2) neonatal castration of male rats permits sprouting in a pattern similar to normal females, and neonatal testosterone treatment of females or castrated males results in the more limited sprouting response characteristic of normal males. These results indicate that the sex-related differential response to fimbrial lesions may be determined by developmental differences in endogenous steroid levels.

The sympathetic superior cervical ganglia as peripheral neuroendocrine centers

The superior cervical ganglia (SCG) provide sympathetic innervation to the pineal gland, cephalic blood vessels, the choroid plexus, the eye, carotid body and the salivary and thyroid glands. Removal of the ganglia brings about several neuroendocrine changes in mammals, including the disruption of water balance in pituitary stalk-sectioned rats, and the alteration of normal photoperiodic control of reproduction in hamsters, ferrets, voles, rams and goats. These effects are commonly attributed to pineal denervation. However pinealectomy does not always mimic ganglionectomy in its neuroendocrine sequelae. This paper discusses several examples illustrating the lack of homology of ganglia and pineal removal, including the prolactin release brought about by gonadal steroids in spayed rats, the changes in drinking behaviour caused by ganglionectomy and the control of goitrogenic response to methylmercaptoimidazole in rats. All these examples indicate that SCG removal, at least as far as for neuroendocrinologists and pineal experimenters are concerned, should not be considered simply as "pineal denervation". A functionally relevant link between SCG and the hypothalamus may occur in rats inasmuch as ganglionectomy depresses norepinephrine uptake and increases the number and responses of alpha-adrenoceptors in medial basal hypothalamus. Lastly the SCG are active points of concurrency for hormone signals, as revealed by the metabolic changes induced by steroid and anterior pituitary hormones in these structures even in the absence of intact preganglionic connections, as well as by the existence of putative receptors for some of the hormones, namely, estradiol, testosterone and corticosteroids. The SCG appear to constitute a peripheral neuroendocrine center.

Interaction of age and sex in sympathetic axon ingrowth into the hippocampus following septal afferent damage

Damage to the medial septal nucleus or to the fimbria/fornix in the adult rat elicits sprouting of vascular sympathetic fibers into the deafferented regions of the hippocampal formation. The following study examines the effects of developmental stage and sex on this sprouting phenomenon using both fluorescence histochemistry and high affinity uptake of noradrenaline. We find that (1) the sprouting, which is reduced in adult and juvenile males relative to females, is equivalent in the two sexes after transections at postnatal day 3, and (2) the period of maximum ingrowth is sexually regulated, occurring near postnatal day 3 in the male and postnatal day 13 in the female.

Age-related changes in catecholamine metabolites of human urine from birth to adulthood

Catecholamines (dopamine [DA], norepinephrine [NE], epinephrine [E]), methoxyamines (3-methoxytyramine [MT], normetanephrine [NMN], metanephrine [MN]), DOPA, and acidic metabolites (3,4-dihydroxyphenylacetic acid [DOPAC], vanilmandelic acid [VMA]) were determined in human urines from one day of age to adulthood, in order to investigate sympatho-adrenal development during life. All adrenergic compounds are present in neonate urines on the first day of life, but their postnatal evolution is quite different according to the nature of metabolites. Daily E, MN and VMA amounts remain low until the 10th month of life; daily NE, MT and DOPA levels increase progressively, but, in contrast, NMN amounts are already high in the neonatal period and increase only beyond the fourth year of age. DA is at either age the predominant catecholamine but its elimination is relatively more important in the neonatal period.