Biomedical subjects

J A Cherry

Publications and source records attributed to J A Cherry.

At least 19 recordsLinked to original sources

PubMed2001

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.

Animals↗

PubMed2001

Diazepam and rolipram differentially inhibit cyclic AMP-specific phosphodiesterases PDE4A1 and PDE4B3 in the mouse.

Cyclic AMP is hydrolyzed by members of at least eight classes of cyclic nucleotide phosphodiesterases (PDEs). Although it has been reported that cyclic AMP PDE activity in mammalian tissues can be inhibited by benzodiazepines, it has not been conclusively demonstrated that members of the class of cyclic AMP-specific, rolipram-inhibitable PDEs (PDE4s) are targets for these drugs. Moreover, no PDE4s expressed in mice have been characterized. To address these issues, we isolated two cDNAs representing homologues of PDE4A1 and PDE4B3 from a mouse brain library. After transient transfection in human embryonic kidney (HEK) 293 cells, the mouse PDEs hydrolyzed cyclic AMP with a low K(m) and were inhibited by rolipram; both are properties typical of other mammalian PDE4 enzymes. In addition, we found that diazepam inhibited cyclic AMP hydrolysis by the mouse PDE4 subtypes. Interestingly, PDE4B was significantly more sensitive to inhibition by both rolipram and diazepam than the PDE4A subtype. This is the first demonstration that recombinantly expressed PDE4s are inhibited by diazepam, and should facilitate future studies with mouse models of depression and anxiety.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Geochemical reactions resulting from in situ oxidation of PCE-DNAPL by KMnO4 in a sandy aquifer.

Although the potential for KMnO4 to destroy chlorinated ethenes in situ was first recognized more than a decade ago, the geochemical processes that accompany the oxidation have not previously been examined. In this study, aqueous KMnO4 solutions (10-30 g/L) were injected into an unconfined sand aquifer contaminated by the dense non-aqueous-phase liquid (DNAPL) tetrachloroethylene (PCE). The effects of the injections were monitored using depth-specific, multilevel groundwater samplers, and continuous cores. Two distinct geochemical zones evolved within several days after injection. In one zone where DNAPL is present, reactions between KMnO4 and dissolved PCE resulted in the release of abundant chloride and hydrogen ions to the water. Calcite and dolomite dissolved, buffering the pH in the range of 5.8-6.5, releasing Ca, Mg, and CO2 to the pore water. In this zone, the aqueous Ca/Cl concentration ratio is close to 5:12, consistent with the following reaction for the oxidation of PCE in a carbonate-rich aquifer: 3C2Cl4 + 5CaCO3(s) + 4KMnO4 + 2H+ --> 11CO2 + 4MnO2(s) + H2O + 12Cl- + 5Ca2+ + 4K+. In addition to Mg from dolomite dissolution, increases in the concentration of Mg as well as Na may result from exchange with K at cation-exchange sites. In the second zone, where lesser amounts of PCE were present, KMnO4 persisted in the aquifer for more than 14 months, and the porewater pH increased graduallyto between 9 and 10 as a resultof reaction between KMnO4 and H2O. A small increase in SO4 concentrations in the zones invaded by KMnO4 suggests that KMnO4 injections caused oxidation of sulfide minerals. There are important benefits of carbonate mineral buffering during DNAPL remediation by in situ oxidation. In a carbonate-buffered system, Mn(VII) is reduced to Mn(IV) and is immobilized in the groundwater by precipitating as insoluble manganese oxide. Energy-dispersive X-ray spectroscopy analyses of the manganese oxide coatings on aquifer mineral grains have detected the impurities Al, Ca, Cl, Cu, Pb, P, K, Si, S, Ti, U, and Zn indicating that, similar to natural systems, precipitation of manganese oxide is accompanied by coprecipitation of other elements. In addition, the consumption of excess KMnO4 by reaction with reduced minerals such as magnetite will be minimized because the rates of these reactions increase with decreasing pH. Aquifer cores collected after the KMnO4 injections exhibit dark brown to black bands of manganese oxide reaction products in sand layers where DNAPL was originally present. Mineralogical investigations indicate that the manganese oxide coatings are uniformly distributed over the mineral grains. Observations of the coatings using transmission electron microscopy indicate that they are on the order of 1 microm thick, and consequently, the decrease in porosity through the formation of the coatings is negligible.

Environmental Pollutants↗

PubMed2001

A controlled field experiment on groundwater contamination by a multicomponent DNAPL: creation of the emplaced-source and overview of dissolved plume development.

A unique field experiment has been undertaken at the CFB Borden research site to investigate the development of dissolved chlorinated solvent plumes from a residual dense non-aqueous phase liquid (DNAPL) source. The "emplaced-source" tracer test methodology involved a controlled emplacement of a block-shaped source of sand containing chlorinated solvents below the water table. The gradual dissolution of this residual DNAPL solvent source under natural aquifer conditions caused dissolved solvent plumes of trichloromethane (TCM), trichloroethene (TCE) and perchloroethene (PCE) to continuously develop down gradient. Source dissolution and 3-D plume development were successfully monitored via 173 multilevel samplers over a 475-day tracer test period prior to site remediation research being initiated. Detailed groundwater level and hydraulic conductivity data were collected. Development of plumes with concentrations spanning 1-700,000 micrograms/1 is described and key processes controlling their migration identified. Plumes were observed to be narrow due to the weakness of transverse dispersion processes and long due to advection and significant longitudinal dispersion, very limited sorptive retardation and negligible, if any, attenuation due to biodegradation or abiotic reaction. TCM was shown to be essentially conservative, TCE very nearly conservative and PCE, consistent with its greater hydrophobicity, more retarded yet having a greater mobility than observed in previous Borden field tests. The absence of biodegradation was ascribed to the prevailing aerobic conditions and lack of any additional biodegradable carbon substrates. The transient groundwater flow regime caused significant transverse lateral plume movement, plume asymmetry and was likely responsible for most of the, albeit limited, transverse horizontal plume spreading. In agreement with the widespread incidence of extensive TCE and PCE plumes throughout the industrialized world, the experiment indicates such solvent plumes are likely to be highly mobile and persistent, at least in aquifers that are aerobic and have low sorption potential (low foc content).

Hydrocarbons, Chlorinated↗

PubMed2001

Surgically induced cryptorchidism-related degenerative changes in spermatogonia are associated with loss of cyclic adenosine monophosphate-dependent phosphodiesterases type 4 in abdominal testes of rats.

The present study was undertaken to investigate the role of phosphodiesterase type 4 (PDE4) enzymes in cryptorchidism-induced apoptosis of the germ cells. Regulation of expression of PDE4 enzymes was studied in the abdominal and scrotal testes of surgically induced cryptorchid rats for 10, 20, and 30 days. In some cases orchidopexy was performed after 30 days of cryptorchidism, and rats were allowed to recover for an additional 50 days. Upon histological examination, marked degenerative changes in the epithelial lining of the seminiferous tubules within abdominal testes were observed compared with contralateral control or age-matched sham-operated rats. These changes included degeneration of some spermatogonia, apoptosis of the secondary spermatocytes, incomplete spermatogenesis, and lack of spermatozoa in the lumen. In contrast, contralateral scrotal testes exhibited normal histology. Significant improvement in the regeneration of spermatogonia was observed in rats after 50 days of recovery following orchidopexy. Immunocytochemical examination suggested the presence of PDE4A in germ cells while PDE4B was predominantly expressed on somatic cells. Western blotting using PDE4 subtype-selective antibodies showed the presence of two PDE4A variants (a 109-kDa PDE4A8 and a previously uncharacterized 88-kDa PDE4A variant) and two PDE4B (78-kDa PDE4B2 and 66-kDa PDE4B variant) bands. In unilaterally cryptorchid animals, the abdominal testis showed a time-dependent decrease in both PDE4A8 and 88-kDa PDE4A variants. In contrast, the expression of 66-kDa PDE4B was markedly increased in a time-dependent fashion in abdominal testes of cryptorchid rats. Animals surgically corrected for cryptorchidism and allowed to recover for 50 days exhibited normal expression of both PDE4A and PDE4B variants compared with aged-matched, sham-operated controls. In conclusion, this study suggests that down-regulation of PDE4A variants in cryptorchid testes may play an important role in the degeneration of spermatogonia and increased apoptotic activity in the germ cells.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2001

Central forebrain Fos responses to familiar male odours are attenuated in recently mated female mice.

Exposure of recently mated female mice to the urinary odours of an unfamiliar male blocks pregnancy (the Bruce effect). The absence of a pregnancy block in response to the stud male's familiar odours depends on an olfactory memory that is formed in the accessory olfactory bulb (AOB) in response to vomeronasal organ (VNO) inputs during mating. Sexually naive Balb/c female mice in pro-oestrus/oestrus were either placed onto soiled bedding ('bedding-only' females) from, or allowed to mate with, a Balb/c male ('recently mated' females). After 42 h, females were placed for 90 min onto clean bedding (controls) or onto soiled bedding from either a C57BL/6 male (unfamiliar bedding) or a Balb/c male (familiar bedding). Significant increases in Fos-immunoreactivity (Fos-IR, a marker of neuronal activation) occurred in the medial amygdala and the medial preoptic area (MPA) of 'bedding only' females exposed to either unfamiliar or familiar bedding and in 'recently mated' females exposed to unfamiliar bedding but not to familiar bedding. This suggests that a mating-induced memory prevents the later activation by the familiar stud male's odours of neurons in forebrain regions that receive inputs from the VNO--AOB. 'Bedding-only' females later exposed to either familiar or unfamiliar bedding had increased Fos-IR in the G alpha(o) protein-expressing basal zone of the VNO whereas no such effect occurred in 'recently mated' females. Familiar, as well as unfamiliar, male odours augmented Fos-IR in significantly more rostral than caudal AOB granule cells in all groups, with the effect being strongest in 'recently mated' females exposed to familiar male bedding. This outcome is consistent with the absence of odour-induced Fos-IR in forebrain regions of these females and, presumably, the absence of a pregnancy block.

Animals↗

PubMed2000

Cyclic AMP phosphodiesterases in the zebra finch: distribution, cloning and characterization of a PDE4B homolog.

Songbirds are important animal models for studying neural mechanisms underlying learning and memory. While evidence has emerged that cAMP plays a significant role in invertebrate and mammalian learning, little is known about the role of cAMP pathways in regulating neuronal function in birds. With the goal of identifying important components of this pathway, we report the first cloning of a cAMP-specific, Type IV phosphodiesterase (PDE4) in a non-mammalian vertebrate. A combination of PCR analysis and cDNA library screening was used to show that homologs of the four known mammalian PDE4 genes also exist in zebra finch. A full-length cDNA representing the zebra finch homolog of PDE4B1 was isolated from a telencephalic library. Expression of this cDNA in human embryonic kidney 293 (HEK) cells yielded an enzyme that hydrolyzed cAMP with a low K(m) and was inhibited by micromolar concentrations of rolipram; these properties are typical of all known mammalian PDE4s. In brain, northern blots revealed transcripts of 3.6 and 4.4 kb in adults, but only the 3.6 kb transcript in juveniles, suggesting that PDE4 expression is developmentally regulated. In situ hybridization of tissue sections demonstrated that PDE4 message was distributed widely throughout the adult zebra finch brain, including regions controlling the learning of songs and the acquisition of spatial memories. These data suggest that PDE4 enzymes may influence a variety of brain functions in these birds and play a role in learning.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2000

Noradrenergic lesions differentially alter the expression of two subtypes of low Km cAMP-sensitive phosphodiesterase type 4 (PDE4A and PDE4B) in rat brain.

This study examined the effects of selective, central noradrenergic dennervation with 6-hydroxydopamine (6-OHDA) on the expression of type 4 phosphodiesterases (PDE4). Twenty-one days following i.c.v. injection of 6-OHDA (200 microg) hypothalamus, neostriatum, and cerebellum were dissected. Infusion of 6-OHDA reduced norepinephrine (NE) content in all the brain areas examined (to 17%, 76% and 16% of sham-operated controls in hypothalamus, striatum, and cerebellum, respectively). 6-OHDA injections also reduced dopamine levels in hypothalamus (53%) and neostriatum (68%). Administration of desipramine (20 mg/kg, i.p.) 30 min prior to 6-OHDA injection protected neostriatal and cerebellar noradrenergic neurons NE levels (110-122% of the control levels). Desipramine partially attenuated the 6-OHDA-mediated decrease in NE content of hypothalamus, but had little or no effect on either striatal or hypothalamic dopamine (DA) levels. Western blot analysis using a PDE4A-selective antibody revealed three major bands (109 kDa PDE4A5, 102 kDa PDE4AX and 76 kDa PDE4A1) in hypothalamus and striatum. Infusion of 6-OHDA decreased the expression of PDE4A5 and PDE4AX but not of PDE4A1 in hypothalamus, as determined by quantitative Western blotting. Pretreatment of rats with desipramine attenuated the 6-OHDA-induced down-regulation of PDE4A5 and PDE4AX bands in hypothalamus. The PDE4B selective antibody K118 labels 5 major bands in all the brain regions studied. One hundred kDa PDE4B3, 86 kDa PDE4B2 and a 78 kDa PDE4B band was identified using recombinant proteins. Treatment of rats with 6-OHDA resulted in a 52% decrease in the PDE4B3 and 58% decrease in 78 kDa PDE4B variant in hypothalamus; administration of desipramine attenuated the 6-OHDA-induced down-regulation of both PDE4B variants. Neither 6-OHDA nor desipramine altered striatal PDE4A or PDE4B isozymes. In contrast, cerebellar PDE4B3 variant is up-regulated by 6-OHDA treatment and were partially normalized to control values by desipramine pretreatment. These data demonstrate that PDE4 subtypes are differentially regulated by presynaptic noradrenergic activity and may play an important role in the maintaining homeostasis of noradrenergic signal transduction in rat brain.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2000

Distribution of PDE4A and G(o) alpha immunoreactivity in the accessory olfactory system of the mouse.

Distribution of the cAMP-specific phosphodiesterase PDE4A was examined in the accessory olfactory system by immunohistochemistry. Adjacent sections through the vomeronasal organ (VNO) and accessory olfactory bulb (AOB) were alternately immunostained with antibodies against PDE4A or the G-protein alpha subunit G(o) alpha, which labels basal VNO neurons, in order to determine whether PDE4A occurs preferentially in one of two segregated VNO pathways. We found that PDE4A strongly labeled apical VNO neurons and rostral AOB glomeruli. There was virtually no overlap in G(o) alpha and PDE4A staining, and there were no regions of the VNO neuroepithelium or AOB glomeruli not labeled by either antibody. These results identify a potential member of the pheromone transduction cascade in apical neurons, and provide further evidence that the VNO consists of functionally distinct pathways.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Cyclic AMP phosphodiesterases are localized in regions of the mouse brain associated with reinforcement, movement, and affect.

Four cyclic AMP-specific, rolipram-inhibited phosphodiesterases (PDE4s) have been identified in mammals; all four are homologs of dunce, a gene required for learning and memory in Drosophila. To determine the distribution of PDE4s in the mammalian brain, specific antibodies were generated against the proteins encoded by each of three dunce homologs PDE4A, PDE4B, and PDE4D in the mouse. On Western blots, these antibodies recognized multiple protein species in all brain regions studied. Immunohistochemical studies showed that both cell bodies and neuropil were well labeled in selected regions throughout the brain. Immunoreactivity for PDE4A was found predominantly in the anterior olfactory nucleus, subiculum, layer V pyramidal neurons from the cerebral cortex, and corticospinal tracts. By contrast, anti-PDE4B-labeled neurons were observed in the inferior olive, the paraventricular and supraoptic nuclei of the hypothalamus, and in the ventral striatum. Regions of neuropil containing high levels of PDE4B immunoreactivity included the cerebellar molecular layer, globus pallidus, nucleus accumbens, and substantia nigra. Anti-PDE4D antibody distinctly labeled cerebellar Purkinje cells as well as neurons in the medial habenula and thalamic nuclei. Fibers in the fasciculus retroflexus, interpeduncular nuclei, and periaqueductal gray were also stained with this antibody. These findings indicate that the distribution of PDE4s in the brain is remarkably segregated, and suggest that each of these enzymes has a unique functional role. Furthermore, the data support the notion that rolipram, the PDE4-specific inhibitor that acts as an antidepressant in humans, may mediate its behavioral effects through PDE4B, which is highly localized to neural pathways known to underlie reward and affect in mammals.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Effective poultry programming in the next century. Balancing research programs: applied and basic.

The generation of new knowledge and the application of that knowledge to benefit mankind are both essential for the land grant university system to maintain viability into the next century. Sources and availability of funding also will dictate both basic and applied approaches. Federal funding initiatives will continue to emphasize competitive grants, hence, more basic research. State and private funding, conversely, often dictate an emphasis on application. Although most universities will continue to conduct more fundamental and applied research, the proper ratio will vary among institutions. The ratio will be influenced by a number of factors, including the philosophy of the institution, age and expertise of the faculty, promotion and tenure requirements, and funding sources.

Agriculture↗

PubMed1999

Vomeronasal neuroepithelium and forebrain Fos responses to male pheromones in male and female mice.

Male urinary pheromones modulate behavioral and neuroendocrine function in mice after being detected by sensory neurons in the vomeronasal organ (VNO) neuroepithelium. We used nuclear Fos protein immunoreactivity (Fos-IR) as a marker of changes in neuronal activity to examine the processing of male pheromones throughout the VNO projection pathway to the hypothalamus. Sexually naive male and female Balb/c mice were gonadectomized and treated daily with estradiol benzoate (EB) or oil vehicle for 3 weeks. Subjects were then exposed to soiled bedding from gonadally intact Balb/c males or to clean bedding for 90 min prior to sacrifice and processing of their VNOs and forebrains for Fos-IR. Male pheromones induced similar numbers of Fos-IR cells in the VNO neuroepithelium of oil-treated male and female subjects; however, EB-treated females had significantly more Fos-IR neurons in the VNO than any other group. There was an equivalent neuronal Fos response to male odors in the mitral and granule cells of the anterior and posterior accessory olfactory bulb of males and females, regardless of hormone treatment. In central portions of the VNO projection pathway (i.e., bed nucleus of the stria terminalis, medial preoptic area) neuronal Fos responses to male pheromones were present in female but absent in male subjects, regardless of hormone treatment. In a separate experiment, mating induced neuronal Fos-IR in these brain regions at levels in gonadally intact male subjects which were equal to or greater than those seen in ovariectomized females primed with estrogen and progesterone. This suggests that neurons in the central portions of the male's VNO pathway are capable of expressing Fos. Our results suggest that sexually dimorphic central responses to pheromones exist in mice that may begin in the VNO neuroepithelium.

Animals↗

PubMed1996

Estrogenic control of preoptic area development in a carnivore, the ferret.

1. Evidence is reviewed which shows that a sexually dimorphic nucleus located in the dorsomedial portion of the male ferret's preoptic area/anterior hypothalamus (POA/AH), called the male nucleus of the POA/AH (Mn-POA/AH), develops during fetal life in response to the action of estradiol, which is formed directly in the nervous system from circulating testosterone over the final quarter of a 41-day gestation. 2. Results are summarized which establish that neurons which make up the Mn-POA/AH are born prior to the critical period of estradiol's action in the male brain. Other data show that some radial glial processes, visualized immunocytochemically using antibodies against GFAP, emanate from proliferative zones at the base of the lateral ventricles in a dorsal-ventral orientation, whereas other glial processes emanate laterally from proliferative zones lining the third ventricle. 3. We suggest that at least some neurons which constitute the dorsomedial POA/AH are born in proliferative zones surrounding the lateral ventricles, raising the question of whether estradiol acts in developing males to influence the migration of these neurons along radial glial guides into the Mn-POA/AH. 4. Finally, evidence is summarized showing that excitotoxic lesions of the dorsomedial POA/AH enhance males' preference to approach and interact with another sexually active male, as opposed to an estrous female, when adult subjects are castrated and treated with estradiol benzoate. These data suggest that the sexually dimorphic Mn-POA/AH is an essential part of a CNS circuit which determines heterosexual partner preference in the male ferret.

Animals↗

PubMed1995

A mouse homolog of dunce, a gene important for learning and memory in Drosophila, is preferentially expressed in olfactory receptor neurons.

The dunce (dnc) gene in Drosophila codes for a cyclic adenosine monophosphate-specific phosphodiesterase (PDE). Flies with a mutation at this locus exhibit severe deficits in learning and memory. We have begun to analyze the neural distribution of mammalian homologs of dnc in the mouse. Surprisingly, in situ hybridization and northern blotting using a probe specific for one of the four mammalian dnc homologs (mPDE2) reveals high levels of expression in the olfactory neuroepithelium. Anti-mPDE2 antibody confirms that this PDE protein is abundant in the axons and dendrites of the olfactory receptor neurons but is conspicuously absent from the cilia, where the initial events in olfactory signal transduction occur. Lower levels of mPDE2 were also detected throughout the brain and in the testis. These findings suggest an important modulatory role for mPDE2 in mammalian olfaction.

Animals↗

PubMed1993

Regulation of protein kinase C activity by sensory deprivation in the olfactory and visual systems.

Environmental regulation of sensory function has provided an important model of plastic mechanisms mediating neural information processing. To define potential commonalities in information processing in different systems, we investigated molecular changes elicited by sensory deprivation in the developing rat olfactory and visual systems. Protein kinase C (PKC), an intracellular messenger implicated in synaptic plasticity and memory, was analyzed. Initial, developmental studies indicated that PKC activity in the soluble and particulate fractions of the olfactory bulb increased three- to fourfold from birth to 3 months of age. Unilateral olfactory deprivation prevented the developmental increase in both soluble and particulate PKC activities in the ipsilateral olfactory bulb and piriform cortex, the second-order relay. Phorbol ester binding localized PKC to intrinsic neuronal populations and their dendrites in the control and deprived bulbs. Moreover, PKC was similarly lower in the visual cortex of dark-reared rats than in light-reared controls. The changes in PKC were region specific, as activity was unchanged by either treatment in the parietal cortex, a control area that does not process primary olfactory or visual information. Our results suggest that the important intracellular messenger, PKC, is similarly regulated in entirely different sensory systems by different environmental stimuli. Consequently, different sensory systems may use common molecular mechanisms to process information.

Animals↗

PubMed1992

Effects of sex and androgen treatment on dendritic dimensions of neurons in the sexually dimorphic preoptic/anterior hypothalamic area of male and female ferrets.

A sexually dimorphic group of cells at the dorsal border of the preoptic/anterior hypothalamic area (POA/AH) of ferrets has been previously identified in Nissl-stained tissue. In this study, Golgi-stained tissue was examined in order 1) to determine whether sex differences exist in dendritic dimensions of neurons from this region, and 2) to assess the effects of adult androgen treatment on dendritic morphology in ferrets of both sexes. Brains from adult ferrets given daily injections of testosterone propionate (5 mg/kg body weight) or oil vehicle for 5 weeks after gonadectomy were impregnated by Golgi-Cox procedures. After sectioning at 120 microns, 78 multipolar neurons were selected from the sexually dimorphic POA/AH of 12 ferrets and reconstructed in three dimensions with the aid of a computer-assisted neuron tracing system. Large sex differences were observed in somal area and most aspects of dendritic morphology, including total length, number of branches, and total dendritic surface area. Androgen also appeared to accentuate dendritic arborization in both sexes, but this effect was weaker than the sex effect, more apparent in males than females, and restricted to fewer variables. The most statistically significant effects of adult androgen treatment in males were found for total dendritic surface area and percentage of fourth order dendrites, and in females, average dendritic thickness. These data show that strong sex differences exist in dendritic structure of neurons in the POA/AH, and suggest that alterations in levels of gonadal steroids in adulthood may promote synaptic remodeling in a region of the brain involved in the control of sexually dimorphic behaviors.

Animals↗

PubMed1991

Neonatal testosterone masculinizes sexual behavior without affecting the morphology of the dorsal preoptic/anterior hypothalamic area of female ferrets.

We examined whether testosterone (T) administered to female ferrets neonatally--a treatment known to enhance masculine coital capacity--induces formation of the sexually dimorphic male nucleus in the dorsal preoptic/anterior hypothalamic area (MN-POA/AH), and/or sensitizes dorsal POA/AH neurons to the stimulatory effect of later androgen treatment on somal dimensions. In males, the MN-POA/AH was present in all subjects, and exposure to androgen following castration at postnatal day 56 (P56) increased both MN-POA/AH volume as well as mean somal areas of MN-POA/AH neurons relative to oil-treated controls. Females given androgen from P5 to P20 and for one month beginning after ovariectomy on P56 failed to develop the MN-POA/AH, but displayed high levels of masculine sexual behavior. Somal areas of dorsal POA/AH neurons in females that received either T or a control neonatally did not increase following androgen treatment at P56. Thus, the correlation that exists between somal enlargement of dorsal POA/AH neurons and masculine sexual behavior in androgen-treated males is not found in behaviorally masculinized females. Masculine coital ability does not appear related to aspects of dorsal POA/AH morphology, supporting data from a previous study in which lesions of the MN-POA/AH caused negligible deficits in masculine sexual behavior of adult male ferrets.

Animals↗

PubMed1990

Effects of lesions of a sexually dimorphic nucleus in the preoptic/anterior hypothalamic area on the expression of androgen- and estrogen-dependent sexual behaviors in male ferrets.

The male nucleus of the preoptic/anterior hypothalamic area (MN-POA/AH) is a sexually dimorphic structure present in male, but not in female ferrets. Ovariectomized female ferrets given increasing dosages of estradiol benzoate (EB) normally run faster towards a stud male in an L-maze (i.e. become more proceptive). In two separate experiments, only gonadectomized males with bilateral damage to the MN-POA/AH following large or small electrolytic lesions approached stud males more quickly in response to EB. By contrast, males which received sham lesions, unilateral large POA/AH lesions, or bilateral lesions which missed the MN-POA/AH on at least one side failed to show EB-induced reductions in approach latencies in pre- or post-operative tests. Males with large POA/AH lesions also displayed significant post-operative decrements in masculine sexual behaviors during treatment with a high dose of testosterone propionate (TP). Less severe, but statistically significant deficits in masculine coital performance were also observed in males with small lesions which damaged the MN-POA/AH bilaterally; however, the ability of these males to achieve intromissions appeared normal. Together, these results suggest that the MN-POA/AH of the male ferret exerts an inhibitory influence on estrogen-dependent proceptive responsiveness, but play only a minor role in the control of masculine coital behavior.

Animals↗