Nares occlusion eliminates heterosexual partner selection without disrupting coitus in ferrets of both sexes.
(65/1479)
Using an airtight Y maze and a new method to induce peripheral anosmia in ferrets, we assessed the contribution of conspecific odors, either alone or in combination with visual and auditory signals, to heterosexual partner preference. Sexually naive ferrets were gonadectomized and treated with sex steroids, after which their nares were either bilaterally occluded using dental impression material or were sham-occluded. Behavioral and histological evidence suggested that nares occlusion blocked access of odors to the main olfactory epithelium for the duration of the study. Sham-occluded females and males preferred to approach odor only or odor plus visual plus auditory cues from opposite-sex conspecifics, whereas nares-occluded ferrets approached opposite- and same-sex cues equally. All ferrets subsequently mated successfully in tests conducted in a small chamber. When retested in the Y maze, sham-occluded females and males again preferred to approach odor-only or odor plus visual plus auditory cues from opposite-sex ferrets, whereas nares-occluded subjects showed no such preference even in tests when a brief physical interaction with tethered stimulus ferrets was allowed after each trial. Our results show that in the ferret, a carnivore, the detection and processing of volatile odors from conspecifics by the main olfactory system is required for heterosexual mate choice. (+info)
Thermoregulatory changes induced by cholinomimetic substances introduced into the cerebral ventricles of sheep.
(66/1479)
1 Thermoregulatory responses have been recorded from Welsh Mountain sheep exposed to warm, neutral or cold environments while injections of cholinomimetic drugs and/or their antagonists have been given into a lateral cerebral ventricle. 2. Carbachol and physostigmine inhibited panting of animals at high ambient temperature (ta), caused vasoconstriction and initiated shivering at neutral ta, and accentuated shivering at low ta. Rectal temperature (tre) invariably increased. Oxotremorine had apparently identical effects. 3. Nicotine and another ganglionic stimulant, the quaternary methyl derivative of dopamine, had no effects on thermoregulation. 4. Atropine given 10 min before injections of carbachol, physostigmine or oxotremorine completely inhibited their hyperthermic effects, but pretreatment with the ganglion-blocking drug, pempidine, caused no inhibition. The cholinergic synapses that respond to cholinomimetic drugs injected into the lateral cerebral ventricles of sheep are therefore muscarinic and not nicotinic. 5. When atropine was given to sheep exposed to cold, no detectable reduction of shivering occurred and tre decreased only slightly, even with doses of atropine far greater than needed to inhibit shivering induced by physostigmine. This may be because shivering is controlled by neural pathways unaffected by drugs administered intracerebroventricularly or because the cholinergic synapses activated by physostigmine do not carry the input from cold sensors. (+info)
Enhanced inactivation of prostaglandin E2 by the rabbit lung during pregnancy or progesterone treatment.
(67/1479)
1. The inactivation of prostaglandin E2 by the rabbit lung was estimated in vivo by comparing its depressor potency following intravenous and intra-aortic injections, and in vitro by measuring the rate of disappearance of smooth muscle stimulating activity when the prostaglandin was incubated with high speed supernatant fractions from lung homogenates. 2. The ability of the lung to inactivate prostaglandin E2 in vivo increased gradually throughout pregnancy, and then decreased rapidly during the three days post-partum. 3. An increased lung inactivation was also seen in pseudopregnant (day 12) rabbits, and in non-pregnant rabbits treated with progesterone for 12 days. A further increase occurred when progesterone treatment was prolonged to 26 days. 4. Treatment with oestradiol monobenzoate or cortisol for 12 days, and deprivation of ovarian hormones for 14-17 days by ovariectomy, were without effect on the lung inactivation of prostaglandin E2. 5. The in vitro experiments revealed a striking increased in the activity of lung prostaglandin metabolizing enzymes during pregnancy. 6. The results are discussed in relation to the hormonal changes occurring during pregnancy, and it is suggested than an enhanced lung inactivation of prostaglandins might have an important protective function at this time. (+info)
Uptake of 3H-progesterone by brain and pituitary of castrated male rats.
(68/1479)
Gonadectomized male rats of Wistar strain were administered 3H-progesterone. Various brain tissues and anterior pituitary were analyzed for retention of radioactivity, using a liquid scintillation technique. Radioactivity, in all tissues, was highest at 20 min after steroid treatment, and thereafter dropped nearly in the same pattern as each other. Among the tissues examined median eminence and anterior pituitary retained more radioactivity for a longer period of time than did other tissues. The results suggest that there is long-term retention of progesterone in the median eminence and anterior pituitary of male rats. (+info)
Altered sexual development in male rats after oestrogen administration during the neonatal period.
(69/1479)
Male rats given 250 mug oestradiol benzoate by subcutaneous injection on Day 4 of postnatal life showed a marked delay in the onset of the pubertal increase in the weight of the testes and seminal vesicles and in spermatogenesis but not a complete failure of sexual development. The increase in plasma testosterone concentration at puberty was also delayed in oestrogen-treated males but the eventual increase in seminal vesicle weight was closely related in time to the delayed increase in plasma testosterone concentration. Both plasma LH and FSH concentrations were reduced for about 10 days after oestrogen administration as compared to control values. After 22 days of age, plasma LH concentration did not differ significantly from the control values. The plasma FSH concentration of the oestrogen-treated males showed a delayed rise to values equal to or higher than those of controls of the same age. The delayed rise in plasma FSH concentration in the oestrogen treated males preceded the delayed rise in plasma testosterone in these animals. The decrease in plasma FSH concentration from the high prepubertal values to the lower values in adults occurred at different ages in the control and in oestrogen-treated rats but in both groups the decrease occurred as plasma testosterone levels were increasing and the first wave of spermatogenesis was reaching completion. The increase in plasma FSH concentration after castration was reduced in oestrogen-treated males during the period throughout which FSH levels in the intact animals were subnormal but the levels in oestrogen-treated males castrated after the delayed rise in FSH had occurred did not differ from control values. It is suggested that the delayed sexual maturation of male rats treated with high doses of oestrogen in the neonatal period is related principally to abnormalities in the secretion of FSH. (+info)
Cyproterone acetate diminishes sexual activity in male rabbits.
(70/1479)
Cyproterone acetate (CA) was injected daily in eleven rabbits for 3 weeks at a dose of 20 mg/day, and for a further week at a dose of 40 mg/day. After 3 weeks of treatment, the ejaculation frequency was reduced but other measures of sexual behaviour were not significantly changed. There was no reduction in the fructose concentration of the semen, but the volume of the ejaculates decreased. The vesicular glands from the experimental animals showed histological changes typical of those occurring after castration. It was concluded that CA reduced the activity of at least one of the accessory sex glands as well as sexual behaviour. This lends support to the current hypothesis that the endocrine regulation of rabbit sexual behaviour differs from that of the rat. (+info)
The role of ovarian steroids in placental development and endovascular trophoblast migration in the golden hamster.
(71/1479)
Pregnant hamsters were ovariectomized on Day 7 and daily supplements of progesterone or progesterone plus oestradiol benzoate were given. Fetal development and survival was 14% and 62% respectively. Histological examination indicated that failure of labyrinthine development in the placenta resulted in failure to form an adequate number of maternal arterial spaces communicating with the base of the trophospongium to allow trophoblast migration in the related maternal spiral arteries. Progesterone was essential at all stages of gestation to sustain decidualized tissues and allow survival of a minority of fetuses. Oestradiol supplementation significantly increased fetal survival, but not to normal levels, suggesting that other oestrogens may be essential for the maintenance of normal hamster pregnancy. (+info)
Effects of 5-hydroxytryptamine on fertility and luteal development following intravaginal administration in the rat.
(72/1479)
Intravaginal administration of 5HT was effective in terminating pregnancy when given after implantation in the rat, provided that the tampon was allowed to remain in the vagina for 4 hr or more. Complete antifertility efficacy was associated with a prevention or reversal of the increase in ovarian weight, which occurs in untreated rats between Days 12 and 17 of pregnancy, and correlates with enlargement of the CL. Data from hysterectomized, ovariectomized and progesterone-implanted rats indicated that the effect on CL was not a cause of the antifertility effect. Intravaginal administration of 5HT was found to lead to general systemic effects. (+info)