Effects of multiple, chronic and early hashish exposure on mating behavior, nest-building and gestation in mice

1. The effects of hashish extract on social behavior were investigated in pairs of mice living together from mating to parturition. The drug was administered orally to both animals at a dose of 20 mg delta 9-tetrahydrocannabinol/kg three times a week, either (I) during the 3 weeks from mating to parturition, (II) during the 12 weeks from weaning to mating and parturition, or (III) only during the 3 weeks after weaning. 2. In the mating tests, an acute administration (I) caused a general sedation. Chronically treated animals (II) showed decreased sexual behavior and lower social investigations despite significantly more non-social activities. Early drug treatment (III) had no effect on mating behavior. In all three series of experiments the females had conceived by the next morning. 3. The nest-building behavior during pregnancy was suppressed after multiple (I) and chronic (II) drug administration. In early drug-treated animals (III) the transport of nesting material was only slowed down. Non-social activities were normal or increased in all three series. 4. Parturition was significantly delayed by one day after multiple (I) and chronic (II) drug administration. The birth weight was not affected, but the litter size was decreased after chronic drug treatment. Early drug administration (III) had no effects on these parameters. 5. In conclusion, whereas tolerance to the sedative effects of hashish developed very rapidly, the drug influences on social behavior were stable. Therefore, discussions on legalization of cannabis should pay attention to the drug effects on social behavior.     

Relation between mating or ovulation and the duration of gestation in dogs

The effects of day of mating and litter size on gestation length in dogs were studied in 36 beagle bitches (age 2-10 yr). The day that plasma progesterone concentrations exceeded 2 ng/mL was considered the day of ovulation; dogs were randomly assigned to be bred once, 1-5 days after the estimated day of ovulation. The interval from mating to parturition was negatively correlated with the number of days from estimated ovulation to mating (P < 0.01). Gestation length (interval from ovulation to parturition) was almost constant at 63.9 +/- 0.2 days (mean +/- S.E.M.), with no significant relationship between the number of fetuses and the duration of gestation.     

Effects of hypothalamic deafferentation late in gestation on lactation and nursing behavior in the rat

Complete deafferentation of the medial basal hypothalamus (MBH) in 13 primiparous Sprague-Dawley rats was performed on or about Day 14 of gestation. The most significant result was a depression in litter growth as evidenced by the marked number of dead pups by the postpartal Day 5 and the loss of weight in those that survived. Control animals deafferented in the same region but only along one side (the incomplete deafferented rats, n = 9) adequately maintained young. Animals in both groups gave birth as expected. There were no significant differences in the latency and duration of retrieving and crouching behaviors. Therefore, nursing behavior appeared normal. Only milk ejection seemed disturbed, judging from the fact that suckling alone could not release milk, oxytocin in addition was needed. Thus, by the methods we employed, the MBH appears to be necessary for lactation but not for nursing behavior in the primiparous rat.     

Testosterone,androstenedione and dihydrotestosterone: Effects on mating behavior of male rats

The relative effectiveness of testosterone, androstenedione, and dihydrotestosterone in maintaining mating behavior following castration of male rats was studied. In Experiment 1 testosterone, but not dihydrotestosterone, was found to maintain mating. In Experiment 2 testosterone and androstenedione were found to be equally effective in maintaining mating. Dihydrotestosterone failed to maintain mating and was no more effective than no treatment at all. Testosterone, androstenedione, and dihydrotestosterone significantly enhanced seminal vesicle and penis weight. In Experiment 3 castrated male rats were administered radiolabeled testosterone, androstenedione, or dihydrotestosterone. Radioactivity was found in hypothalamic and seminal vesicle samples indicating that these steroids can be accumulated by brain as well as peripheral androgen-sensitive tissues. It was concluded that the peripherally active steroid dihydrotestosterone probably plays no role in the maintenance of sexual behavior.     

Induction of ovulation, mating, and conception in androgen-treated immature rats

Attempts were made to induce pregnancy in androgen-treated immature rats. Treatment with PMSG alone, which causes ovulation in normal immature rats, failed to cause ovulation in androgenized rats. However, treatment with PMSG plus LHRH was effective in causing ovulation. After ovulation, some of the normal and androgenized rats mated. Normal mated rats became pregnant but androgenized mated rats did not. However, when a pituitary gland was transplanted from a normal rat into the kidney capsule of an androgenized rat to maintain functional corpora lutea, implantation occurred in some of the mated animals. The positive decidual reaction in the uteri of such androgenized rats was similar to that observed in normal rats. These results suggest that the uterine sensitivity to blastocyst implantation of androgenized immature rats may be normal.     

Effects of gestation and lactation on rat gastric fundus

This study evaluated the effects of gestation and lactation on stomach growth in rats. Constant increases were observed in gastric fundus weight during pregnancy and lactation, with a maximum obtained after 3 weeks of lactation. This increase in tissue weight was not associated with hyperplasia of the gastric fundus as in no instance did total DNA contents from mated females differ significantly from those of the unmated controls. Mild hypertrophy, as evidenced by significant increases in cellular mass and RNA and protein concentrations, was observed during late lactation. Gastrin might be responsible for these modest changes in the gastric fundus.     

The effect of mating on the afternoon of proestrus on serum LH (and FSH) and ovulation in the rat

Possible relationships between coitus and serum gonadotrophin levels and ovulation in the rat were investigated. Female rats were mated betw een 1700 and 1730 or between 1800 and 1830 hours. 1.3 ml of blood was withdrawn by cardiac puncture 30 minutes postcoitus for luteinizing hormone (LH) analysis. After autopsy on the morning of estrus, counts were made of tubal ova, and LH and follicle-stimulating hormone (FSH) were measured in terminal blood from all animals. Those mated at 1700-1730 with no cardiac puncture showed significantly more ova than those with cardiac puncture (p less than .05) and those which were neither mated nor received cardiac puncture (p les than .05). No differences were found between those mated at 1800-1830 hours because of the large variance in each group. Coitus during the time of normal mating did not increase LH levels 30 minutes postmating or terminal LH and FSH levels. Terminal LH levels were significantly increased in the no cardiac puncture-no mate animals (p less than .05) in comparison with the cardiac puncture-no mate animals.     

Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 +/- 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 +/- 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 +/- 1 or 71 d +/- 1 d of gestation for evaluation of reproductive performance. Age (190 +/- 3 d vs 195 +/- 3 d) and body weights (106 +/- 2 kg vs 106 +/- 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 +/- 0.7 vs 12.9 +/- 0.9, P = 0.31) and 71 d (13.9 +/- 0.6 vs 12.4 +/- 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 +/- 0.7 vs 9.7 +/- 0.7) but not at 71 d (10.0 +/- 1.1 vs 9.6 +/- 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.     

三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响

近年来越来越多研究表明,雄性产生精子(精液)也需付出代价。在多次交配的动物中,雄性为获得最大生殖潜力,必须依据配偶的质量策略性地调整每次交配的生殖投入。雄性策略性的生殖投入主要体现在两个方面,一是精子竞争(sperm competition),二是柯立芝效应(Coolidge effect)。目前精子竞争研究主要集中于昆虫类群,而柯立芝效应研究集中于高等脊椎动物,同时验证结果也时常与假说不一致。以多次交配的三突伊氏蛛为材料,以雄蛛交配行为为指标,在蜘蛛类群中探讨和验证雄性精子竞争强度假说和柯立芝效应。设定3个交配组合:2只雄蛛依次与1只雌蛛各交配1次(A组)、2只雄蛛依次与2只雌蛛各交配1次(B组)和1只雄蛛与1只雌蛛交配2次(C组),分析比较3个交配组合的三突伊氏蛛第1次交配和第2次交配在交配潜伏期、交配持续时间和交配回合数方面的差异,比较三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响,以此验证雄性精子竞争强度假说和柯立芝效应。研究结果表明A和B组的三突伊氏蛛第2次交配的交配潜伏期和交配持续时间显著长于第1次交配。同时,C组的三突伊氏蛛第1次交配的交配潜伏期和交配持续时间与第2次交配都没有显著差异。同时,A、B和C组的三突伊氏蛛第1次交配的交配回合数与第2次交配都没有显著差异。研究结果支持精子竞争强度假说,而不支持柯立芝效应。     

Effects of variations in the male copulatory behavior on ovulation and implantation in prairie voles, Microtus ochrogaster

The effects of copulation on ovulation and implantation were studied in the prairie vole (Microtus ochrogaster). Both 1 and 2 ejaculatory series induced ovulation in 9 of 10 females. 2 ejaculatory series resulted in slightly fewer corpora lutea and implanted embryos, and in a slightly greater incidence in intrauterine mortality. In the first ejaculatory series, the likelihood of ovulation increases with increased numbers of intromissions and ejaculatory thrusts. Vaginal penetration is required for the induction of ovulation. The congruence of male copulatory behavior and female reproductive physiology would seem to indicate a coadapatation among this species.     

Effects of caffeine on mating behavior and sperm precedence in Tribolium castaneum

Biogenic amines such as dopamine are physiologically neuroactive substances that affect behavioral and physiological traits in invertebrates, and it has long been known that these substances affect mating behavior in insects. Caffeine is a dopamine activator and thus enhances dopamine receptor activity. However, the effects of caffeine intake on insect mating behavior have been largely unexplored. Therefore, we examined the effect of caffeine on mating behavior in the red flour beetle Tribolium castaneum. Caffeine, which activates dopamine, affected the mating behavior of T. castaneum males. Males who orally ingested caffeine courted faster than males who did not, resulting in faster mounting of females and less time to a male's external aedeagus protrusion. However, the present results showed no difference in sperm precedence measured as a P2 value between males fed caffeine and males not fed caffeine. We discuss the effects of caffeine on insect mating and the possibility that caffeine consumption may cause males to mate with more females in the laboratory.     

Effects of ventromedial nucleus lesions on estradiol induced ovulation in the rat

Small bilateral stereotaxic lesions were made in the hypothalamic ventromedial nucleus (SVMN) to determine: (i) whether estrogen would restore early receptivity in unreceptive SVMN lesioned female rats and (ii) whether SVMN lesions would suppress estrogen induced ovulation in the rat. SVMN lesions were shown to completely suppress spontaneous early receptivity and seriously impair estrous receptivity in 5-day cyclic female Wistar rats. A loss of early receptivity in response to 10 μg estradiol benzoate (EB) was also observed in SVMN lesioned females, in comparison to unoperated, sham VMN and dorsomedial nucleus (DMN) lesioned animals. Isolated SVMN lesioned females exhibited a weak ovulatory response to 10 μg EB, but, where shown to be unreceptive prior to estrogen injection, they never ovulated. On the contrary, ovulation occured in about 50% of cases in isolated unoperated and in sham VMN and DMN lesioned females following estrogen administration. The mechanisms whereby EB brought about precocious ovulation in 5-day cyclic female rats were therefore concluded to be dependent on VMN functional integrity and thereby on the degree of early sexual receptivity in the rat.     

Prostaglandins and the rat seminal vesicle: Effects of mating and adrenergic stimulation

The concentrations of PGE, PGF, and 6-keto-PGF_1α were increased in rat seminal vesicle tissue following mating activity. Likewise, synthesis of PGE and PGF was stimulated by epinephrine (3 × 10⁻⁷to 3 × 10⁻⁶ M) in tissues and media from incubations of intact rat seminal vesicles. The stimulation was inhibited by phentolamine, an α-adrenoreceptor blocking agent. Carbamylcholine (2 × 10⁻⁶ M) and bradykinin (1 × 10⁻⁶ M) had no effect on PGE or PGF synthesis, even though both compounds stimulated contractility of the rat seminal vesicle at these concentrations. These data suggest that mating and adrenergic stimulation increase prostaglandin synthesis in] the rat seminal vesicle, probably through an α-adrenergically mediated mechanism.