Plasma cocaine levels and locomotor activity after systemic injection in virgin and in lactating maternal female rats

We have determined the temporal pattern of plasma cocaine levels and increased activity that result from acute systemic injections of cocaine to female rats in two different endocrine and behavioral states, in nonmaternal virgins and in lactating maternal dams. Plasma levels of cocaine as well as ambulatory and rearing activity were determined every 30 min for a total of 300 min after subcutaneous injections of either 10, 20, or 40 mg/kg of cocaine. Virgin females had no prior drug history, whereas lactating, maternal dams had received two cocaine injections before activity testing. Within 30 min after an injection, cocaine in the plasma and activity were substantially elevated, and generally remained so for 270-300 min. Overall, plasma cocaine levels and activity were well correlated and followed a predictable dose-response pattern. The onset, peak, duration, and decline of activity corresponded generally to the onset, peak, duration, and decline of plasma cocaine. For virgins, mean ambulatory activity increased 2.5-4.0-fold over baseline, whereas in lactating females activity increased 5-11-fold over baseline. Stereotypy did not occur. Although the general responsivity of these females to cocaine was very similar to that reported for males, there are differences in the timing of peak activity and the return of activity to baseline when the virgins and the lactating dams are compared to each other and to reports by others on male rats. These data support the hypothesis that endocrine or behavioral state may influence the responsiveness of animals to cocaine.     

Muscle metabolism of professional athletes using 31P-spectroscopy

PURPOSE: Cocaine abuse has reached epidemic proportions in the United States. Our recent study has shown that cocaine has adverse action on spermatogenesis and fertility in male rats. The indirect action of cocaine occurs by blocking the reuptake of neurotransmitter, which causes local vasoconstriction. In this study we evaluate blood flow to the testes after subcutaneous injection of cocaine to male rats. METHODS: Male Sprague-Dawley rats were divided into two main groups. The treatment group received subcutaneous cocaine (30 mg/kg body weight) and the control animals received normal saline. Xenon-133 wash out experiments were carried out on testes at 5, 10, 15, 20, 30, 45, 60, 90 min and 4.5 hours after injection of cocaine or normal saline. Statistical analysis was done by SPSS V. 7.S for windows. P < 0.05 was considered statistically significant. RESULTS: There was a reduction in testicular blood flow after cocaine administration to male rats. This vasoconstrictor effect was most pronounced at 15 min after injection of cocaine and persisted up to 60 min. At 90 min, the early restitution of blood flow to ischemic tissue occurred. There was a significant increase in testicular blood flow in cocaine-treated groups than in the control group during restitution phases at 90 min. At 4.5 hours, there was no difference in blood flow in both groups. CONCLUSION: This study demonstrates that cocaine, when given subcutaneously at a 30 mg/kg body weight dose, results in prolonged vasoconstriction of the blood vessels to the testes. Adverse effects of cocaine on the testes may be in part due to ischemic and postischemic reperfusion injury to the organ.     

Attenuation of cocaine-induced locomotor activity by butyrylcholinesterase.

A primary enzyme for the metabolism of cocaine is butyrylcholinesterase (BChE). To determine whether the systemic administration of BChE can increase the metabolism of cocaine sufficiently to alter a behavioral effect, rats were tested in a locomotor activity chamber after receiving 17 mg of cocaine per kg intraperitoneally. In rats pretreated intravenously with 5,000 IU of horse serum-derived BChE, the locomotor activity effect was significantly attenuated. BChE pretreatment increased plasma BChE levels approximately 400-fold. When added to rat plasma, this amount of BChE reduced the cocaine half-life from over 5 hr to less than 5 min. BChE altered the cocaine metabolic pattern such that the relatively nontoxic metabolite ecgonine methyl ester was produced, rather than benzoylecgonine. These results suggest that systemic administration of BChE can increase the metabolism of cocaine sufficiently to alter a behavioral effect of cocaine and thus should be investigated as a potential treatment for cocaine abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Altered ACTH and corticosterone responses to interleukin-1 beta in male rats exposed to an alcohol diet: possible role of vasopressin and testosterone

We have previously shown that female rats exposed to an alcohol (ethanol, E) diet exhibited a blunted ACTH response to systemically administered interleukin-1 beta (IL-1 beta). Because of the presence of gender differences in the activity of the hypothalamic-pituitary-adrenal (HPA) axis, and of the possible role played by sex steroids in modulating the inhibitory influence of E in females, we studied the ability of a 10-day E diet to alter ACTH and corticosterone secretion of intact or castrated male rats injected with IL-1 beta or endotoxin, a releaser of endogenous cytokines. Pituitary responsiveness to secretagogues that mediate the endocrine effects of IL-1 beta, namely corticotropin-releasing factor (CRF) and vasopressin (VP), was also investigated. The ACTH responses of animals fed ad libitum (C group) or pair-fed (PF group) to the intravenous administration of IL-1 beta or endotoxin were not statistically different (p > 0.05); therefore, results from these two groups were combined in the initial experiments. Subsequent experiments only used E and C animals. When compared with this latter group, intact E males showed a significant (p < 0.01) decrease in ACTH levels measured 30 and 60 min after the intravenous injection of IL-1 beta or endotoxin. In contrast, E rats released as much corticosterone as C rats in response to IL-1 beta, but significantly (p < 0.05) more following administration of endotoxin (lipopolysaccharide). The stimulatory effect of VP on ACTH release was also measurably blunted by alcohol, whereas that of CRF was not. In none of these experiments were any significant differences observed between C and PF rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of chlordiazepoxide on low-rate behavior are gender dependent

Gender differences in anxiety have long been assumed to exist, but the experimental evidence is contradictory. It has also been suggested that antianxiety agents may have gender-dependent behavioral effects. The present experiment was designed to establish whether or not intact male and female rats behave differently when exposed to a Differential-Reinforcement of Low-Rate 72-s schedule of reinforcement (assumed to assess some of the inhibitory behavioral tendencies associated with anxiety), and whether or not the behavioral effects of acute chlordiazepoxide administration would differ between the sexes. There were no differences between male and female rats in the total number of responses, the total number of obtained reinforcers, or response efficiency in the absence of drug administration. Male and female Wistar rats were then challenged with different doses of chlordiazepoxide (vehicle, 1, 3, 10, 17, and 30 mg/kg). Low doses of chlordiazepoxide (1 and 3 mg/kg) decreased response efficiency, and medium doses (10 and 17 mg/kg) increased response efficiency in male and female rats. The highest dose of CDP (30 mg/kg) further increased response efficiency in male rats, but decreased response efficiency in female rats. These results suggest that the behavioral effects of chlordiazepoxide are dose dependent and that the effects of a large dose of chlordiazepoxide differ between male and female rats. Whether or not gender differences in drug metabolism or whether schedule contingencies played an important role in these observations remains to be determined in future experiments.     

Pharmacokinetic evaluation of liposomal encapsulated ampicillin in male and female rats

The dispositions of free and liposomal entrapped ampicillin were compared in male and female rats after i.v. administration. Serial blood samples were collected for 2 h in the free drug study and 12 h for the liposomal formulation. Pharmacokinetic parameters obtained with free drug were not significantly different between genders. However, gender significantly influenced the disposition of liposomal encapsulated ampicillin. While no difference was observed in distribution t1/2 between genders, female rats had a shorter MRT, smaller Vss and Vt, and faster clearance as compared to male rats. In a second study, spleen, liver, kidney, heart, and lung were harvested post-injection of free and liposomal entrapped ampicillin. Free ampicillin did not distribute extensively into the tissue compartment and no gender difference was noted. In contrast, liposomal encapsulation resulted in a substantial tissue uptake. In general, female rats had higher concentrations in the spleen and lung as compared to male rats. In vitro plasma stability was not significantly different, suggesting that destabilization of the liposomes does not play a large role in the dispositional differences observed in these studies. However, in vivo interaction of liposomes and plasma lipoproteins may influence the disposition of encapsulated drug.     

Acute abstinence effects following smoked cocaine administration in humans.

Acute abstinence symptomatology following multiple deliveries of smoked cocaine was examined. Twelve crack cocaine users (male and female) participated in an inpatient study. Participants smoked 7 deliveries of cocaine on each of 4 experimental days, with each participant being exposed twice to 2 dose sizes of cocaine (0.40 vs. 0.07 mg/kg "placebo"). Symptoms of cocaine abstinence were measured for 6 hr following cocaine administration and again the following morning. Participants reported feeling increased craving, anxiety, and uncertainty 30 min after the 7th delivery of 0.40 mg/kg cocaine, when cocaine plasma levels were still on the descending curve. It is not clear whether these were true abstinence effects or were due to residual effects of cocaine. No significant differences were found at subsequent abstinence-assessment points. These data indicate that acute abstinence effects from smoked cocaine in a laboratory setting may be minimal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disposition and metabolism of [3H]cocaine in acutely and chronically treated dogs

1. Beagle dogs were chronically treated with cocaine, 5 mg/kg subcutaneously twice daily for 6 weeks, followed by same dose of [3H]cocaine given intravenously. 2. The t1/2 values of cocaine in plasma, liver, spleen and heart, in acutely and chronically treated dogs, were: 1-2, 1-1; 2-2, 1-8; 1-8, 1-3; 2-0, 1-2 h, respectively. In both groups, cocaine disappeared from all areas of the central nervous system 12-24 h after injection but significant amounts of radioactivity due to benzoylnorecgonine and benzoylecgonine persisted in the CNS even 1 week after administration of cocaine. Brain-to-plasma ratios of cocaine were lower in chronically-treated than in acutely-treated dogs 2 and 4 h after injection. 3. Norcocaine, benzoylnorecgonine, benzoylecgonine and ecgonine were metabolites of cocaine in dog brain in both groups. Norcocaine and benzoylnorecgonine were present in higher amounts in brains of chronically treated dogs. Rate of disappearance of norcocaine was similar to cocaine in both groups. 4. The amounts of cocaine excreted in urine and faeces as percentage of dose were 0-9-5-0, 1-1-6 in the acute and 2-2-3-3 and 0-2-0-3 in the chronically treated dogs. Major excretion of radiactivity occurred in urine within 24 h in both groups. Total radioactivity (65% of dose) in urine plus faeces was similar in both groups. 5. Norcocaine, benzoylnorecgonine, benzoylecgonine, ecgonine, norecgonine, ecgonine methyl ester and unidentified compounds were urinary metabolites of cocaine in both groups. Benzoylnorecgonine and ecgonine were excreted in higher amounts and benzoylecgonine and norecgonine in lower amounts in the acute than in the chronically treated dogs. 6. The possible role of persistence of benzoylnorecgonine and benzoylecgonine (which possessed potent stimulant activity intracisternally) in the CNS is discussed.     

Cocaine and metabolites in amniotic fluid may prolong fetal drug exposure

OBJECTIVE: Cocaine and metabolites can be found in the amniotic fluid after maternal use, presumably as a result of fetal urination. The fetus may be repeatedly exposed to the effects of these drugs through contact with amniotic fluid that contains these substances. The purpose of this study was to determine whether the naive fetal lamb generates detectable fetal blood levels of cocaine and metabolites when cocaine is placed directly into the amniotic fluid and, if so, whether fetal swallowing accounts for these findings. STUDY DESIGN: Six pregnant ewes with singleton fetuses of 120 to 125 days' gestation were chronically catheterized for daily sampling of cocaine and metabolite levels in maternal venous plasma, fetal venous plasma, and amniotic fluid over a 7-day period. Esophageal ligation was performed in three additional animals similarly instrumented to evaluate the role of fetal swallowing in the distribution of amniotic fluid cocaine and its metabolites. In each case, at the time of surgery, an Alzet osmotic pump delivering cocaine at 0.5 mg/kg estimated fetal weight per hour into the amniotic fluid was secured to the fetal back. Cocaine and metabolites (benzoylecgonine, ecgonine methyl ester, and norcocaine) were measured daily in material and fetal plasma, amniotic fluid, and meconium by solid-phase extraction and derivatization and quantified by high-performance gas chromatographic techniques. RESULTS: The concentrations of ecgonine methyl ester were highest in the amniotic fluid followed by cocaine and benzoylecgonine. In the normal and esophagus-ligated groups, cocaine, benzoylecgonine, and norcocaine were found in fetal plasma in concentrations of approximately 3% that of amniotic fluid. Ecgonine methyl ester was not detected in fetal plasma from either group. Meconium samples from sheep with and without esophageal ligation demonstrated high levels of norcocaine. CONCLUSION: We conclude that cocaine and metabolites in amniotic fluid enter the fetal circulation to produce detectable plasma levels through routes other than swallowing. Moreover, the results of meconium analyses in the two groups of fetuses suggest that fetal swallowing is not the primary mechanism by which cocaine and metabolites enter the intestine.     

Selective uptake of intact parathyroid hormone by the liver: differences between hepatic and renal uptake

Hepatic and renal extraction of immunoreactive parathyroid hormone (i-PTH) was studied in awake dogs with explanted kidneys and chronic indwelling hepatic vein catheters. After a single injection of bovine PTH 1-84 (b-PTH 1-84), hepatic arteriovenous (A-V) differences for immunoreactive PTH (i-PTH) was 39% at 2 min after injection but decreased to 0% by 25 min, despite high levels of i-PTH in the arterial circulation. Gel filtration of arterila and hepatic venous samples obtained when hepatic A-V differences for i-PTH were demonstrable revealed hepatic uptake of the intact hormone and addition of a smaller COOH-terminal fragment, eluting just after the intact hormone, to the hepatic venous blood. Gel filtration of samples obtained 20-30 min after injection of b-PTH was demonstrable) revealed no detectable intact hormone in the circulation. Levels of COOH-terminal fragments of the hormone at the time were identical in arterial and hepatic venous samples. In additional experiemtns no hepatic A-V difference was observed after the injection of the synthetic bovine PTH 1-34 (syn b-PTH 1-34). By comparison there was a demonstrable A-V difference of 20% across the kidney for both intact PTH and COOH-terminal fragments that persisted until i-PTH disappeared from the circulation. The kidney also demonstrated an A-V difference of 22% after injection of syn b-PTH 1-34. These studies demonstrate selective extraction of intact PTH but not of its fragments by the liver. The kidney, on the other hand, extracted the intact hormone and both COOH and NH2 terminal fragments. The studies demonstrate that the kidney was the only organ of those examined that detectably removed the fragments of PTH from the circulation.     

Molecular cDNA cloning and tissue distribution of mRNA encoding a novel ATP-binding cassette (ABC) half-transporter

After feeding a commercial rodent chow for 8 weeks, tissues from male and female rats were collected and examined for selenium content, glutathione peroxidase (GPX) activities and selenoprotein W (Se-W) levels. There were no differences (P > 0.05) between plasma selenium content, plasma GPX activity, whole blood selenium content, or whole blood GPX activity between male and female rats. There was also no gender effect on selenium concentration in muscle, brain, spleen, and skin, but selenium concentration in liver was higher (P < 0.05) in female than in male rats. Western blots indicated that the tissue distribution of Se-W was similar in male and female rats. Se-W protein level was high in testes of male rats but very low in ovaries of female rats. Muscle and skin from female rats had significantly higher (P < 0.05) Se-W levels than from male rats. Consistent with Se-W content, the Se-W mRNA levels from female skins were significantly higher (P < 0.05) than from male rats. The expression of Se-W was different in various tissues and gender influenced this regulation in some tissues.     

Concurrent pharmacokinetic analysis of plasma cocaine and adrenocorticotropic hormone in men

The purpose of this study was to determine the covariance between plasma cocaine and ACTH pharmacokinetics. Twelve healthy male occasional cocaine users participated in a double blind study. Intravenous cocaine (0.2 mg/kg) or placebo was infused over 1 min, and samples for cocaine, ACTH and cortisol analysis were collected at 2, 4, 8, 12, 16, 20, 30, 40, 60, 80, 120, 180, and 240 min. Peak cocaine plasma levels averaged 101.2 +/- 14.6 ng/mL. ACTH increases were significantly correlated (P < 0.0001) with increases in plasma cocaine levels (r = 0.67; r2 = 0.44). Pharmacokinetic analysis showed that the t(max) (observed time to maximum concentration) values for cocaine (6.0 +/- 1.4 min) and ACTH (7.3 +/- 1.2 min) were almost identical. The area under the curve was calculated using the trapezoidal rule. The area under the curve for plasma cocaine was 6463 +/- 1070 ng/min x mL, and the area under the curve for ACTH was 1873 +/- 188 pmol/min x L. The mean half-life for plasma cocaine was 46.7 +/- 4.0 min, and that for ACTH was 35.8 +/- 5.1 min. Cardiovascular and subjective effect measures were correlated with concurrent increases in plasma cocaine and ACTH levels.     

Gender differences in ethanol preference and ingestion in rats. The role of the gonadal steroid environment

An ethanol oral self administration paradigm showed the existence of gender differences in alcohol preference in rats: whereas males and females initiated alcohol drinking at similar rates, females maintained their preference for ethanol over a longer duration. Neonatal estrogenization of females, which effectively confers a male phenotype on a genetically female brain, resulted in patterns of drinking that were similar to those displayed by intact male rats, indicating that gender differences in alcohol drinking patterns may be, at least partially, accounted for by sexual differentiation of the brain. To test whether gonadal steroids also exert activational effects on ethanol-seeking behavior, we also examined the effects of gonadectomy alone, or in combination with gonadal steroid replacement therapy. Castration did not significantly alter ethanol consumption in males, although treatment of castrated rats with dihydrotestosterone resulted in a significant inhibition of this parameter. As compared with the situation in intact female rats, ethanol ingestion was significantly reduced in ovariectomized female rats receiving estradiol (E2) and in ovariectomized female rats receiving combined E2 and progesterone replacement therapy. However, neither ovariectomy nor progesterone replacement in ovariectomized rats resulted in ethanol drinking patterns that were different compared to those observed in intact female controls. Thus, dihydrotestosterone and E2, respectively, appear to exert modulatory influences on the male and female rats' preference for ethanol, but further investigations are necessary to determine to what extent these effects result from activational actions on the brain.     

Conditioned facilitation of brain reward function after repeated cocaine administration.

Cocaine lowers brain reward thresholds, reflecting increased brain reward function. The authors investigated whether, similar to acute cocaine administration, cocaine-predictive conditioned stimuli would lower intracranial self-stimulation (ICSS) thresholds. Rats received a saline injection for 5 days, a cocaine injection (10 mg/kg) for 20 consecutive days, then saline for 5 additional days. Thresholds were measured immediately before and 10 min after each injection. The initial 5 saline injections had no effect on thresholds, whereas cocaine significantly lowered thresholds for 20 days. There was no tolerance or sensitization to this effect of cocaine over days. During the last 5 days when cocaine administration was substituted with saline, rats demonstrated a conditioned lowering of thresholds during the 2nd daily ICSS session. These data demonstrate that cocaine-predictive conditioned stimuli induce a conditioned facilitation of brain reward function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Regulation of sulfotransferase mRNA expression in male and female rats of various ages

Sulfotransferases (SULTs) are Phase II drug-metabolizing enzymes that catalyze the addition of a sulfuryl moiety to both endogenous compounds, including steroids and neurotransmitters, and certain xenobiotics, including N-hydroxy-2-acetylaminoflourine and phenolic compounds, like alpha-naphthol. In contrast to certain Phase I drug-metabolizing enzymes, little is known about the regulation of the sulfotransferases. These series of studies were designed to analyze SULT mRNA expression and hormonal regulation in male and female rats. The hepatic expression of six different SULT isoforms was examined including three phenol SULTs and three hydroxysteroid SULTs. SULT mRNA expression was examined in adult and developing rats, as well as, in hypophysectomized (HX) and growth hormone-supplemented HX animals. SULT1A1 is thought to be important for the sulfation of simple phenols and its mRNA expression is about twice as high in adult male as in female rats. This difference in SULT1A1 mRNA levels is largely due to a greater decrease in mRNA levels after puberty in female than in male rats. Hypophysectomy resulted in a decrease in expression of SULT1A1 mRNA in both male and female rats. Replacement of growth hormone (GH) by either intermittent injection (male pattern) or infusion (female pattern) failed to restore SULT1A1 expression. Sulfotransferase SULT1C1 has been implicated in activation of N-hydroxyacetylaminoflourine. In contrast to SULT1A1, SULT1C1 mRNA expression is about 10-fold higher in adult males than in adult female rats. This male-dominant expression pattern emerges at 40-50 days of age and is due to an increase in SULT1C1 mRNA in males. Hypophysectomy abolished SULT1C1 expression in male rats. Interestingly, replacement of GH by injection (male pattern) restored SULT1C1 mRNA expression in males and enhanced SULT1C1 expression in female rats to levels observed in adult male rats. GH infusion (female pattern) did not affect SULT1C1 mRNA expression in either male or female rats. Estrogen sulfotransferase (SULT1E2) may play a role in estrogen homeostasis. Adult male rats express SULTIE2 mRNA at levels 10-fold higher than those observed in adult females and similar to SULT1C1, this is due to an increase in SULT1E2 mRNA occurring during puberty in the male rat. Hypophysectomy did not appreciably affect SULT1E2 expression in male rats, however in contrast to males, hypophysectomy markedly enhanced SULT1E2 expression in female rats. GH infusion suppressed SULT1E2 levels in HX male rats. The expression of hydroxysteroid sulfotransferases was also examined. The SULT-20/21 isoform was expressed in both male and female rats. Male expression of this isoform peaked at 30 days of age and then declined to approximately 30% of the level observed in adult females. SULT-20/21 mRNA expression increased sharply at 45 days of age in female rats and remained elevated. Expression of SULT-20/21 mRNA was decreased markedly by hypophysectomy in both male and female rats. GH injection did not affect SULT-20/21 mRNA expression in HX males, however this treatment resulted in a 4-fold increase in SULT-20/21 mRNA in HX females. GH infusion restored SULT-20/21 expression in HX-male rats. GH infusion did elevate SULT-20/21 mRNA expression in female-HX rats, but not to the level observed in intact females. Hydroxysteroid SULT isoform SULT-40/41 was expressed in adult female but not adult male rats. SULT-40/41 expression peaked at 15 days of age in both male and female rats and decreased thereafter. The decrease in expression was more pronounced in male rats. SULT-60 mRNA, like SULT-40/41, was expressed only in adult female rats. Male rats express SULT-60 at 30 days of age, but SULT-60 mRNA is undetectable at 60 days. SULT-60 mRNA was expressed in females only after day 30 and female SULT-60 mRNA expression remains high thereafter. SULT-40/41 and SULT-60 mRNA expression was increased by HX in male rats and decreased by HX in female rats. (ABSTRACT TRUNCATED)     

Apoptosis mediated by Fas and its related diseases]

This study discusses the effect of gammahydroxy butyric acid (GHB) on growth hormone (GH) secretion changes in cocaine addicts. Ten male cocaine users and 10 normal controls were tested with a single oral administration of GHB at a dose of 25 mg/kg body weight. Cocaine addicts were tested before and after 30 days of abstinence. All subjects underwent a control with a placebo. Basal GH levels were similar in normal controls and cocaine users and remained unmodified during the control test. In the normal control subjects, plasma GH levels rose significantly after the administration of GHB; in contrast, plasma GH concentrations failed to increase after GHB treatment in cocaine addicts. These data show that a chronic abuse of cocaine induces alterations of the GABAergic system which were unmasked by the absent GH response to GHB.     

Effects of oestradiol-18beta, hypophysectomy and age on cytoplasmic oestradiol-17beta receptor sites in rat testis interstitial tissue

After administration of oestradiol-17beta to intact mature and immature rats, a decrease in the testicular concentration of specific oestradiol-binding sites was observed within 1 h. The binding capacity was replenished starting about 3 h after oestradiol administration and after 5 h the oestrogen receptor level had returned to control values. Exposure of intact animals to oestradiol-17beta for longer periods (up to 24 h) did not result in an increase of receptor levels in testicular cytosol. Mature animals which were hypophysectomized for periods of up to 10 days did not show a significant change in the number of specific oestradiol-binding sites in either total testicular tissue or dissected interstitial tissue. At 15 days or longer periods after hypophysectomy, an apparent increase in receptor concentrations in total testicular cytosol was observed due to a relative increase in the amount of interstitial tissue. A specific oestradiol-binding protein is present in plasma of immature male rats aged less than 30 days. This plasma protein could also be demonstrated in the cytosol of testes of immature rats. In contrast to the cytosol receptor, which shows a moderate affinity for diethylstilbestrol (DES), the plasma protein did not bind DES. The sedimentation values of the plasma protein and the oestradiol receptor were 4 S and 8 S respectively. These differences in characteristics made it possible to demonstrate the presence of the oestradiol receptor in addition to the binding protein in testicular cytosol of rats from 14 days of age onwards. The nuclear receptor for oestradiol-17beta could be demonstrated after incubation of testicular tissue of rats from 4 days of age onwards.     

Effects of chronic ethanol consumption and withdrawal on the neuroactive steroid 3alpha-hydroxy-5alpha-pregnan-20-one in male and female rats

Prolonged alcohol (ethanol) consumption leads to the development of alcohol tolerance and cross-tolerance to some benzodiazepines and barbiturates. In contrast, rats undergoing alcohol withdrawal are sensitized to the anticonvulsant effects of the endogenous GABA(A) receptor modulator, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP). Alterations in endogenous, cerebral cortical levels of 3alpha,5alpha-THP during alcohol withdrawal could contribute to the observed sensitization to 3alpha,5alpha-THP. Therefore, this study investigated plasma and brain levels of 3alpha,5alpha-THP, progesterone, and corticosterone during alcohol dependence and withdrawal in the rat. Plasma corticosterone, progesterone (a precursor of 3alpha,5alpha-THP) and 3alpha,5alpha-THP levels were unchanged in alcohol-dependent animals. Cerebral cortical levels of 3alpha,5alpha-THP decreased in dependent male animals, but not in dependent female rats. During alcohol withdrawal, plasma corticosterone and progesterone levels increased in male, but not female rats. However, neither plasma nor cerebral cortical 3alpha,5alpha-THP levels were altered from control levels in male or female rats during alcohol withdrawal. Plasma and brain levels of 3alpha,5alpha-THP were markedly higher in female compared with male rats. Cerebral cortical levels of 3alpha,5alpha-THP during the diestrus phase of the estrus cycle were approximately 4 to 6 ng/g, a concentration that may approach physiological relevance. These findings suggest that sensitization to 3alpha,5alpha-THP during alcohol withdrawal is not mediated by elevations in brain levels of endogenous 3alpha,5alpha-THP in male or female rats. However, elevations in circulating corticosterone and progesterone levels during ethanol withdrawal in male rats may underlie gender differences in allopregnanolone sensitivity during ethanol withdrawal.     

Repeated cocaine augments excitatory amino acid transmission in the nucleus accumbens only in rats having developed behavioral sensitization

Rats were pretreated with daily cocaine or saline injections for 1 week. The rats treated with daily cocaine were separated into two groups: a sensitized group of animals demonstrating > 20% increase in motor activity on the last injection compared with the first injection of daily cocaine, and a nonsensitized group showing < 20% elevation. At 2-3 weeks after the last daily injection, four experiments were performed to assess changes in excitatory amino acid (EAA) transmission in the nucleus accumbens produced by repeated cocaine administration. (1) Rats were challenged with a microinjection of AMPA into the shell or core of the nucleus accumbens. The sensitized rats demonstrated greater motor activity than did the saline-pretreated or nonsensitized animals after AMPA injection into either subnucleus. (2) It was shown that the behavioral distinction between sensitized, nonsensitized, and control rats in behavioral responsiveness to AMPA was not mediated by differences in AMPA-induced dopamine release. (3) The extracellular content of glutamate was measured after a cocaine challenge given at 21 d of withdrawal. Cocaine elevated the levels of glutamate in the core of sensitized rats, but not of nonsensitized or control rats. (4) Microinjection of the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione into the core abolished the augmented motor response to a cocaine challenge in sensitized rats, but was without effect on cocaine-induced motor activity in nonsensitized animals. These results indicate that repeated cocaine administration increases EAA transmission in the nucleus accumbens only in rats that develop behavioral sensitization to cocaine.     

Effects of novelty and pain on behavior and hippocampal extracellular ACh levels in male and female rats

In vivo microdialysis was used to assess the effects of novelty and pain on hippocampal ACh release in male and female rats. Experiments were carried out during the dark phase and consisted of 2 days of tests: on Day 1, after Baseline 1, animals were exposed to a new cage (Novelty) to which, 30 min later, a plastic cylinder (Object) was introduced. On Day 2, after Baseline 2, the Formalin test (50 microl of formalin 10%, s.c. injected in the dorsal hindpaw) was carried out in the animal's home cage. All behaviors were recorded. The extracellular levels of ACh in the dorsal hippocampus were estimated, in 10-min samples, by assay of ACh in the dialysates by HPLC. On Day 1 the raw values of ACh were higher in females than in males, but no sex difference was present when the percentage of change was considered. In both sexes the Novelty and Object tests induced an increase in ACh levels with respect to Baseline. Higher levels of exploration were present in females than males during the first 10 min of Novelty. On Day 2, ACh release increased in both sexes during the Formalin test. No sex difference in either ACh raw values or the percentages of change were found. Females showed higher levels of licking and lower levels of activity than males. The present study shows that novelty and pain induce similar hippocampal cholinergic activation in male and female rats but different behaviors. The results are discussed in light of the several anatomical and functional sex differences present in the hippocampus.