Opposite effects of acute and repeated administration of desmethylimipramine on adrenergic responsiveness in rat pineal gland.

The effect of acute and repeated desmethylimipramine (DMI) treatment on catecholamine-stimulated production of adenosine 3', 5'-monophosphate (cyclic AMP) in rat pineal gland was studied $\text{in}$$\text{vivo}$. In rats exposed to continuous illumination, the administration of isoproterenol (2μmol/kg) to control animals produced a marked increase in the concentration of cyclic AMP in pineal gland. In contrast, norepinephrine (2μmol/kg) failed to increase the levels of cyclic AMP. After acute treatment with DMI (single injection, 38μmol/kg, i. p.), the isoproterenol-induced rise in cyclic AMP was not significantly different from that measured in control animals. However, acute DMI treatment did allow a significant elevation in the concentration of cyclic AMP in pineal gland in response to norepinephrine. In rats given nine injections of DMI (38μmol/kg, i.p., twice daily) neither isoproterenol nor norepinephrine caused a significant increase in the concentration of cyclic AMP in pineal glands. Although acute treatment with DMI had no significant effect on [³H] dihydroalprenolol binding, chronic treatment with DMI significantly reduced [³H] dihydroalprenolol binding in the pineal gland. The results of this study suggest that while a single administration of DMI can enhance adrenergic responses elicited by norepinephrine, chronic administration of DMI leads to compensatory decreases in receptor density and adrenergic responsiveness.     

Control of estrogen and androgen receptors in the rat pineal gland by catecholamine transmitter

Sucrose gradient studies of rat pineal cytosol incubated with ³H-estradiol (female pineals) or ³H-5 α -dihydrotestosterone (male pineals) revealed a radioactivity peak in the 8 S region which disappeared after superior cervical ganglionectomy or incubation with excess unlabeled hormone. Ganglionectomy decreased significantly estradiol and testosterone uptake by the pineal gland $\text{in vitro}$ as well as high affinity binding to pineal cytoplasmic and nuclear components. Norepinephrine treatment counteracted all the effects of ganglionectomy but was unable to modify hormone uptake and binding by the pineal gland of sham-operated controls. Pre-treatment with actinomycin D or propranolol but not with phentolamine impaired norepinephrine effects; propranolol blockage however was only partial. Administration of isoproterenol, L-dopa or phentolamine increased hormone uptake by denervated pineals. The effects of isoproterenol were also observed $\text{in vitro}$ and were blocked by propranolol. These results indicate that sex steroid receptors in the pinealocytes are controlled by norepinephrine via beta-adrenergic receptors and that depletion of neural norepinephrine enhanced responsiveness of pineal hormone receptors to exogenous catecholamines.     

Sex-related differences in the nuclear population of postpubertal rat pineal gland. A quantitative study.

Male and female parenchymal pineal cell types have been studied throughout postpubertal development to determine the existence of sex-related differences on a time basis. Six age groups (2, 3, 4, 8, 15 and 24 months) of eight rats (4 males and 4 females) were used in this study. Nuclei of both parenchymal pineal cell types were counted in 5 areas of 26.377 microns 2 per pineal gland on semithin sections. Nonparametric statistics of our results (Mann-Whitney U-test and Kruskal-Wallis H-test) demonstrated significant differences between male and female pinealocytes through the stages studied. In all age groups, the number of nuclei per unit area was larger in female rats. Pineoglial cells did not show significant sex-related differences.     

Electric field stimulation releases norepinephrine and cyclic GMP from the rat pineal gland.

Electrical field stimulation caused the release of preloaded ³H-norepinephrine and of cyclic GMP from the rat pineal gland. Increased release of catecholamines and of cyclic nucleotide occurred at low frequency and current, and was largely dependent on the presence of intact nerve endings and extracellular calcium. Presynaptic synthesis and release of cyclic GMP appears to accompany the exocytotic release of neurotransmitter.     

Effect of aspartic acid on control of ventilation in androgenized and ovariectomized female rats.

Previously we observed that acute subcutaneous administration of aspartic acid (580 mg/kg) depressed ventilation in awake male, but not female, rats, suggesting that this agent may be used as a marker for sexual dimorphism in the control of ventilation. Moreover, males castrated postpubertally showed a response similar to that of intact male rats. Thus the hormonal milieu of male rats appear not to be necessary to elicit the masculine type of ventilatory response to aspartic acid. The purpose of this study was 1) to determine whether adult female rats androgenized by the administration of testosterone propionate (TP) 1 day after birth would alter their ventilation in response to aspartic acid to be more malelike and 2) to compare these results with those of intact (I) and ovariectomized (O) female rats. Minute ventilation and O2 consumption in air and in response to aspartic acid administration were evaluated in awake animals in all three groups. Furthermore the minute ventilation of all rats to a hypercapnic challenge was also evaluated. Ovariectomy resulted in rats increased body weights but decreased weight-corrected ventilation and O2 consumption compared with TP-treated and I animals. Minute ventilation after hypercapnic challenge in the three groups was similar. TP-treated rats responded to aspartic acid administration with a marked depression of ventilation similar to that previously noted in males, whereas neither I nor O rats showed such a response. The depression of ventilation in the TP-treated group in response to aspartic acid was not a consequence of a depression of O2 consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

No short-term effects of high-frequency electromagnetic fields on the mammalian pineal gland

There is ample experimental evidence that changes of earth-strength static magnetic fields, pulsed magnetic fields, or alternating electric fields (60 Hz) depress the nocturnally enhanced melatonin synthesis of the pineal gland of certain mammals. No data on the effects of high-frequency electromagnetic fields on melatonin synthesis is available. In the present study, exposure to 900 MHz electromagnetic fields [0.1 to 0.6 mW/cm², approximately 0.06 to 0.36 W/kg specific absorption rate (SAR) in rats and 0.04 W/kg in Djungarian hamsters; both continuous and/or pulsed at 217 Hz, for 15 min to 6 h] at day or night had no notable short-term effect on pineal melatonin synthesis in male and female Sprague-Dawley rats and Djungarian hamsters. Pineal synaptic ribbon profile numbers (studied in rats only) were likewise not affected. The 900 MHz electromagnetic fields, unpulsed or pulsed at 217 Hz, as applied in the present study, have no short-term effect on the mammalian pineal gland. Bioelectromagnetics 18:376–387, 1997. © 1997 Wiley-Liss, Inc.     

Sex dimorphism in the thyroid gland. IV. Cytologic aspects of sex dimorphism in the rat thyroid gland

This study was designed to explain whether the sex-dependent differences in the structure of the thyroid gland of adult male and female rats depend on quantitative or qualitative changes in the thyroid follicular cells. Absolute thyroid gland weight was similar in male and female rats, but its relative weight was markedly higher in females however. Volume fractions of epithelium and stroma were higher and that of colloid lower in male than in female rats and the epithelium/colloid ratio was higher in the males. Also absolute the volumes (in mm3) of epithelium and stroma were higher in the males; the thyroid gland of females contained more colloid. The average volume of a thyroid follicular cell, estimated by stereology, was higher in males than in females, although the thyroid gland contained similar numbers of follicular cells in both sexes. Also, thyroid glands from both male and female rats contained a similar DNA quantity. Results of the present study show that the sex dimorphism in the rat thyroid depends upon a difference in the mean volume of thyroid follicular cells, with males having larger cells than females. However, in both sexes the thyroid gland contains a similar quantity of these cells.     

Gonadal steroid modulation of neuroendocrine transduction: A transynaptic view

Summary 1. Steroid hormones act on neuronal communication through different mechanisms, ranging from transynaptic modulation of neurotransmitter synthesis and release to development and remodeling of synaptic circuitry. Due the wide distribution of putative brain targets for steroid hormones, acute or sustained elevations of their circulating levels may affect, simultaneously, a variety of neuronal elements. In an elementary mode of interaction, steroids are able to modulate both the synthesis and release of a neurotransmitter at a particular synapse, and the response of its target postsynaptic cells. Using two neuroendocrine transducing systems—the rat pineal gland and the GT_1–7 cell line—we have examined these interactions and the following findings are discussed in this article.2. In the rat, pineal melatonin production is partially controlled by gonadal hormones. In females, melatonin synthesis and secretion is reduced during the night of proestrus, apparently as a consequence of elevated estradiol and progesterone levels. In males, circulating testosterone seems to be necessary to maintain the amplitude of the nocturnal melatonin peak.3. Some gonadal effects on pineal activity are exerted on its noradrenergic input, since changes in circulating steroid hormone levels are able to induce acute modifications of tyrosine hydroxylase activity in pineal sympathetic nerve terminals.4. Gonadal steroids are also able to regulate the response of pineal cells to adrenergic stimulation, since in vivo treatment of both male and female rats with steroid hormone blockers induces profound modifications in adrenergically-induced accumulation of cyclic AMP (cAMP) in dispersed pinealocytes.5. Direct exposure of pineal cells from gonadectomized female and male rats to estradiol (E₂) or testosterone (T), respectively, potentiates pinealocyte response to adrenergic activation. In addition, short-term (15 min) exposure to either progesterone (Pg) or progesterone coupled to bovine serum albumin (P-3-BSA) suppresses the E₂-dependent potentiation of adrenergic response in female rat pinealocytes.6. Exposure of GT_1–7 cells to E₂ completely blocked the norepinephrine (NE)-induced elevation of cAMP content. In E₂-treated GT_1–7 cells, additional exposure (15 min) to either Pg or P-3-BSA abolished E₂-dependent inhibition of NE responsiveness. In addition, P-3-BSA alone increased basal cAMP levels in GT_1–7 cells, regardless previous exposure to E₂.7. In conclusion, there are evidences, both from the current literature and from the present results, supporting the view that in some neuroendocrine systems gonadal hormones modulate neurotransmission by acting, simultaneously, at pre- and postsynaptic sites. The models presented here constitute appropriate examples of this transynaptic mode of steroid action and, therefore, may offer a useful approach to investigate steroid hormone actions on the brain.     

Effects of naloxone and acetylcholine on medial thalamic and cortical units in naive and morphine dependent rats.

The administration of 0.5 mg of testosterone propionate (TP) for 3 days to castrated male rats caused ³H-leucine incorporation into pineal proteins to increase significantly by 79%. TP effects depended on time of administration; rats receiving TP at 06.00 h exhibited a significant 150% increase in pineal protein synthesis 24 h later whereas rats injected at 14.00 h only showed a 54% increase in ³H-leucine incorporation into proteins. Superior cervical ganglionectomy decreased pineal testosterone uptake $\text{in vitro}$ by 21% and pineal protein synthesis by 27%; in addition it blocked the stimulatory effects of TP on protein synthesis. Ganglionectomy also modified the $\text{in vitro}$ metabolism of testosterone by pineal cells; it increased the amounts of ³H-androstenedione and decreased ³H-5∝-androstanedione extracted from pineal glands incubated with ³H-testosterone. These results indicate that the sympathetic nervous input reaching the pineal via the superior cervical ganglia is important to modulate the early steps of androgen action on the pinealocytes.     

Sex differences in prostaglandin metabolism.

Prostaglandin E2 (PGE2), PGF2alfa and PGD2 were synthetized from [1-¹⁴C]-arachidonic acid by rat kidney medulla microsomal fraction. The formation of each prostaglandin was significantly less in female animals than in males. The rate of inactivation of [³H]-PGF2alfa by kidney cortex cytosol was almost linear with the time of incubation during the first 30 min. The production of PGF2alfa metabolite (13,14-dihydro-15-keto PGF2alfa) was higher in male rats than in females.     

Sex-specific interactions between aggressive and sexual behavior in the rat: Effects of testosterone and progesterone

The influence of progesterone on sexual and aggressive behaviors during aggressive encounters was investigated in pairs of TP-treated male and female rats. Gonadectomized females, chronically injected with testosterone propionate (TP), showed low but consistent levels of feminine sexual behavior which alternated with aggression. Progesterone when given in addition to TP facilitated receptive and proceptive behaviors, but reduced levels of aggression. In TP-treated males, levels of aggression were the same as observed in TP-treated females. However, TP-treated males seldomly showed sexual behavior during aggressive encounters and additional treatment with progesterone did not affect their behavior. After the aggression tests, animals were tested in a social preference test in which an ovariectomized female cage mate and the opponent from the aggressive encounter served as incentives. Positive correlations between levels of aggression and social preference for an opponent were found in both sexes, although correlations only reached statistical significance when progesterone was given in addition to TP. These correlations were found in both sexes, despite the fact that group analysis revealed pronounced sex differences in social preference: males preferred to spend their time near ovariectomized female cage mates, whereas females divided their time equally among female cage mates and opponents.     

Gender differences in β‐adrenoceptor system in cardiac hypertrophy due to arteriovenous fistula

This study was undertaken to determine alterations in the β‐adrenoceptor (β‐AR) signaling system in male and female rats at 4 weeks after the induction of arteriovenous (AV) fistula or shunt. AV shunt produced a greater degree of cardiac hypertrophy and larger increase in cardiac output in male than in female animals. Increases in plasma levels of norepinephrine and epinephrine (EPI) due to AV shunt were also higher in male than females. While no difference in the β₁‐AR affinity was seen in males and females, AV shunt induced increase in β₁‐AR density in female rats was higher than that in males. Furthermore, no changes in basal adenylyl cyclase (AC) V/VI mRNA levels were seen; however, the increase in EPI‐stimulated AC activities was greater in AV shunt females than in males. AV shunt decreased myocardial β₁‐AR mRNA level in male rats and increased β₂‐AR mRNA level in female hearts; an increase in G_i‐protein mRNA was detected only in male hearts. Although GRK2 gene expression was increased in both sexes, an increase in GRK3 mRNA was seen only in AV shunt female rats. β‐arrestin1 mRNA was elevated in females whereas β‐arrestin 2 gene expression was increased in both male and female AV shunt rats. While these data demonstrate gender associated differences in various components of the β‐AR system in cardiac hypertrophy due to AV shunt, only higher levels of plasma catecholamines may account for the greater increase in cardiac output and higher degree of cardiac hypertrophy in males. J. Cell. Physiol. 226: 181–186, 2010. © 2010 Wiley‐Liss, Inc.     

Estradiol modulation of pineal gland activity in the wild bandicoot rat, Bandicota bengalensis

In the present study, the effect of estradiol dipropionate on the cytology and mitotic activity of the pineal gland was evaluated in adult ovariectomized and juvenile bandicoot rats, Bandicota bengalensis. Estradiol treatment for 5 days inhibited the ovariectomy-induced hypertrophy of the pineal gland, and increased the nuclear diameters of pinealocytes in juvenile males while having no effect on the pineal cytology of juvenile females. Estradiol injection induced mitosis in the pinealocytes of adult ovariectomized and juvenile bandicoot rats. Thus, estradiol exhibited a dual action (stimulatory and inhibitory) on the pineal gland of this wild rat.     

Sex differences in adrenocortical structure and function

Summary The zonation and cellular composition of the adrenal cortex of intact mature male and female rats of different strains (Chbb Thomm, CFY) and three strains of Wistar rats (W1, W2 and W3) at the age of 84–90 days were compared using morphometry.Both absolute and relative adrenal gland weights were higher in female than male rats. Rats of W3 and Chbb Thomm strains had the largest adrenals. These differences depended upon the higher volume of the zona fasciculata (ZF) and zona reticularis (ZR) in the W3 and Chbb Thomm strains than in the remaining animals. Females had larger adrenocortical zones than corresponding males. The average volume of the ZF cell ranged in males from 1589 m³ (W1 strain) to 2111 m³ (Chbb Thomm) and in females from 2249 m³ (W1 strain) to 2894 m³ (W3 strain). The average nuclear volume of the ZF cells was higher in female rats whereas there were no strain-and sex-differences in the size of zona glomerulosa (ZG) and ZR cells.The total number of parenchymal cells per pair of adrenals varied markedly among the studied strains, with the highest number in W3 and Chbb Thomm females. W3, Chbb Thomm and CFY females had larger number of parenchymal cells than males; the reverse was true for W1 strain whereas no differences were found among W2 male and female rats.     

Adrenal-mediated depression of N-acetyltransferase activity and melatonin levels in the rat pineal gland

N-acetyltransferase (NAT) is believed to be the rate-limiting enzyme in the synthesis of melatonin from serotonin in the pineal gland. Norepinephrine released from sympathetic nerve endings within the pineal gland stimulates NAT activity and, therefore, melatonin synthesis. When an animal is subjected to a stressful stimulus, it would be expected that the increase in plasma stimulus, it would be expected that the increase in plasma catecholamines originating from the adrenal medulla and/or the sympathetic nervous system would result in a stimulation of pineal NAT activity. Adult male rats were given a 1.5cc injection of physiological saline subcutaneously into the back leg. Compared to non-injected controls, animals stressed in this manner were shown to have significantly lower pineal melatonin content 10 min after the saline injection late in the light phase of the light/dark cycle (at 18.30 h-lights on at 07.00 h). To test this more thoroughly, a time course study was conducted during the dark phase (at 02.00 h-5 hours after lights out) when pineal NAT activity and melatonin levels are either increasing or elevated. NAT activity and melatonin levels in the pineal were significantly depressed in stressed animals as compared to controls by 10 min after the saline injection, and remained so until 60 min after injection. By 90 min they had returned to control values. In the next study the nighttime response of the pineal to stress was compared in intact and adrenalectomized rats. Adrenalectomy prevented the changes in NAT activity and melatonin content associated with the saline injection. Some factor, such as a catecholamine or corticosterone from the adrenal, seems to be eliciting the response in the pineal to the saline injection. It is not known if the factor is acting centrally or directly on the pineal gland.     

Hormonal differentiation of sexual behavior in Japanese quail

The effect of hormones on the development of Japanese quail during the postembryonic period was examined. First, subcutaneous implants of estradiol monobenzoate (EB) and testosterone propionate (TP) were implanted 6–12 hr after hatching. EB and TP had no effect on the differentiation of sexual behavior in genetic males or females. However, EB had marked feminizing effects on plumage in genetic males. Second, the role of gonadal hormones during development was examined by gonadectomizing males and females 6–12 hr after hatching and treating them intramuscularly with EB or TP as adults. EB-treated adult females displayed sexual behavior typical of the genetic female and developed female plumage. A significant proportion of TP-treated females (57%) displayed male sexual behavior patterns. Cloacal gland development and male-type vocalizations were induced. EB-treated males displayed either male or female sexual patterns depending on the stimulus conditions. Third, to test whether bisexuality in gonadectomized males and females is maintained despite steroid treatment and expression of sexual behavior in adulthood, gonadectomized quail which were originally treated with EB received TP and vice versa. The results indicate that in the absence of gonadal hormones after hatching female quail remain bisexual until exposed to estrogen, whereas gonadectomized male quail retain behavioral bisexuality irrespective of prior estrogen or androgen exposure.     

Neonatal Androgen Affects Copulatory Behavior in the Female Musk Shrew

The role of neonatal testosterone in the development of copulatory behavior was examined in an insectivore, the musk shrew (Suncus murinus). Female musk shrews were treated with testosterone propionate (TP) for the first 5 days of life and then tested in adulthood for either female or male-like copulatory behavior. Early TP had a masculinizing effect; neonatally treated animals mounted a stimulus female more frequently, and with shorter latencies, in response to adult testosterone treatment than did control females. Neonatally androgenized females also showed deficits in female sexual behavior; few received ejaculations from stud males. This difference was likely caused by increased aggression exhibited by the neonatally TP-treated females toward males. In turn, female aggression decreased efficiency of male partners' intromission attempts. Early TP treatments also caused structural abnormalities in the ovaries, but did not effect their capacity to ovulate in response to either gonadotropin-releasing hormone or human chorionic gonadotropin injection. In sum, exposure to TP during development augmented display of male-like behavior in females and had subtle deleterious effects on expression of feminine behavior.     

Frequency of cocaine administration affects behavioral and endocrine responses in male and female Fischer rats.

Accumulating evidence has shown disparate behavioral responses to cocaine in male and female rats. To date, there is a lack of understanding of how cocaine administration frequency affects sexually dimorphic behavioral responses. In the present study we investigated the behavioral and endocrine responses to single (1 x 15 mg/kg) and "binge" (3 x 15 mg/kg) cocaine administration in male and female Fischer rats. Overall, females showed a more prolonged and robust behavioral response to both acute and "binge" pattern cocaine administration. Furthermore, sex-dependent behavioral topographies emerged during binge-pattern cocaine administration; female rearing activity increased across "binge" injections while ambulatory activity decreased. In contrast, male ambulatory and rearing behaviors remained constant across injections of "binge" cocaine. At the hormonal level, both single and "binge" pattern cocaine administration decreased testosterone levels in male rats. However, cocaine's modulation of testosterone levels was transient since testosterone levels were decreased by cocaine 30 min but not 3 hr following a single injection. In both male and female rats, "binge" cocaine increased plasma progesterone levels. However, acute cocaine administration increased progesterone levels transiently in only female rats. Our results show that pattern of administration affects both cocaine-stimulated behavioral and endocrine responses in male and female rats.     

Induction of ear wiggling in the estrous female rat by gonadectomized rats treated with androgens and estrogens

Intact and gonadectomized male and female rats treated with estradiol and/or dihydrotestosterone were introduced into the cage of estrous female rats. For 3 min the number of periods with ear wiggling displayed by the estrous female and the total duration of the periods with ear wiggling were recorded. It was found that estrous females showed about twice as much ear wiggling in the presence of intact males as in the presence of gonadectomized male and female rats. However, gonadectomized male and female rats treated with dihydrotestosterone induced as much ear wiggling as intact males did. In contrast, administration of estradiol to the gonadectomized stimulus rats did not affect the rate of ear wiggling of the estrous females. Estrous females showed the lowest rate of ear wiggling in the presence of intact female rats. It has been suggested that dihydrotestosterone-treated male and female rats have an odor which sexually excites estrous female rats.     

The role of male accessory-gland substance on female reproduction with some observations of spermatogenesis in the stable fly

The bulbous tubular portion of the median ejaculatory duct functions as the accessory gland in the male stable fly, Stomoxys calcitrans. The gland started to enlarge after emergence when the fly was fed on sugar-water or blood. Implants of accessory glands from sugar-water or blood-fed males were effective in stimulating oviposition in virgin females. The injection into females of accessory-gland extracts from males fed blood prevented insemination; this extract was effective in concentration as low as 0.25 gland per female. Accessory-gland extracts from sugar-water fed males were only partially effective in preventing female insemination. However, the accessory-gland extracts of male stable flies had little effect on insemination when injected into three other species of female dipterans.Spermatogenesis was completed by the time of emergence, or shortly thereafter, a process independent of blood feeding. Three types of spermatids were identified, forming a continuum of spermiogenesis stages. Fat, fusiform spermatozoa elongated to become thin, elongate and mature spermatozoa.