Camillo Vellano

Prolactin and sexual behaviour in the crested newt (Triturus cristatus carnifex Laur.)

Abstract In an attempt to elucidate the possible prolactin involvement in sexual behaviour in the male crested newt, we have devised three experimental approaches: (1) hypophysectomy followed by replacement therapy with prolactin; (2) ectopic pituitary autograft; and (3) treatment with ergocryptine. After hypophysectomy (1), the percent time spent in courtship falls rapidly and is restored partially only by exogenous prolactin. In the short-term ectopic pituitary autograft (2), the enhanced release of endogenous prolactin triggered by the operation exerts a stimulatory effect on sexual behaviour. Courtship behaviour declines in the subsequent days. In long-term operated animals, spermatophore deposition is suppressed and concurrent testes regression takes place. After ergocryptine treatment (3), the percent of time spent in courtship decreases and is restored partially by exogenous prolactin. Hence prolactin appears to control sexual behavior in the crested newt, although other hormones seem to be involved in this mechanism. The occurrence of a synergism between prolactin and gonadal hormones in sustaining sexual behaviour in the crested newt is suggested. The action of prolactin on peripheral organs also is discussed.

Tail height, a prolactin-dependent ambisexual character in the newt (triturus cristatus carnifex Laur.) ☆

Abstract In castrated as well as in castrated and thyroidectomized Triturus cristatus carnifex adults from both sexes, prolactin administration alone (100 IU per newt), unlike LH or TSH, was seen to promote the increase in tail height, which is a seasonal gonadal hormones-independent ambisexual character. The same effects were seen to be exerted in the summer, or in aestivating normal newts by exogenous prolactin, or by treatments enhancing endogenous prolactin production, such as a drop in temperature and ectopic pituitary autografts. The naturally occurring seasonal variations in tail height parallel the circumannual prolactin level variations and water drive. Consistent changes are entailed by prolactin in both the fin connective axis (swelling and pigment redistribution in chromatophores) and the epidermis (acceleration of the mitotic rhythm and slowing down of keratinization processes). The present results lead us to conclude that the seasonal ambisexual character here investigated, the height of the tail, is prolactin dependent. The parallelism between water drive and tail height variations is stressed.

Androgen control of male sex behavior in the crested newt (Triturus cristatus carnifex Laur.): Castration and sex steroid administration

Castration significantly lowers serum testosterone in sexually active male Triturus cristatus. Replacement therapy by implants of testosterone in silastic capsules elevates the serum testosterone level to higher values than normal. Sex behavior is depressed by castration and partially reinstated by replacement therapy with testosterone. 5 alpha-dihydrotestosterone was the only testosterone metabolite showing some behavioral effectiveness in castrates; estradiol and 5 beta-dihydrotestosterone failed to elicit sex behavior.

Sex steroid profile and plasma vitellogenin during the annual reproductive cycle of the crested newt (Triturus carnifex laur.)

The annual reproductive cycle of the crested newt, Triturus carnifex, has been studied in the field. Temperatures, rainfall, humidity, and photoperiod were recorded throughout the year. Adult male and female newts were sampled monthly; snout vent lengths, crest heights of males, and body ovarian, oviducal, testicular, and abdominal gland weights were recorded. Plasma samples were assayed for androgen, estradiol-17 beta, and progesterone by radioimmunoassay and for vitellogenin by enzyme-linked immunosorbent assay. Air, deep water, water surface, and soil temperatures were low from October to March, but increased in April and May without consistent summer variations. Ovarian and oviducal weights increased in October to reach maximum values between January and March (reproductive period). Crest height and abdominal gland weight in males mirrored the ovarian and oviducal pattern, while testicular weights were maximal in October and November. In females, plasma androgens were high during the reproductive period, and plasma estradiol peaked sharply in March, while plasma progesterone changed little. In the males plasma androgen and estradiol concentrations were similar to those of females, while plasma progesterone was significantly correlated with the cycle in testicular weight. In both sexes androgens showed a significantly negative correlation with air and water surface temperature. Plasma vitellogenin peaked in March but it did not correlate with either ovarian weight or plasma estradiol concentrations. These data support and confirm those previously reported for newts under laboratory conditions. The negative correlation between androgens and temperature suggests that this hormone may trigger the reproductive process. Moreover the correlations between plasma progesterone and testicular weight may indicate that this hormone is involved in male newts reproduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigonadal effects of prolactin in adult male crested newt (Triturus cristatus carnifex Laur.)

Abstract In adult estivating male newts ( Triturus cristatus carnifex Laur.) the administration of 100 IU of prolactin (ovine, N.I.H. P-S-7; “Luteolactin” Richter) elicits the same effects as those occurring naturally at the onset of the declining phase of spermatogenesis, i.e., water drive, and cessation of spermatogenesis following the pycnotic degeneration of spermatogonia that are about to change into primary spermatocytes. It is suggested that the latter phenomenon is due to the inhibition of the production of pituitary FSH by prolactin.

Identification by immunofluorescence of prolactin-producing cells in the hypophysis of the newt, Triturus cristatus carnifex Laur

Abstract In sections of the pituitary of the newt treated with fluorescent antiprolactin globulin, a green fluorescent antigen-antibody complex is present only in the acidophilic cells localized in the dorsocentral region of the distal lobe. These cells are identifiable with type I acidophils according to Mazzi (1949) and with type II acidophils according to van Oordt (1968) . These results are in keeping with the observation that purified newt prolactin obtained by polyacrylamide disc electrophoresis reacts immunologically with rabbit antisheep prolactin antiserum.

Gonadotropin stimulation by chronic administration of synthetic luteinizing hormone-releasing hormone in hypophysectomized pituitary grafted male newts

Abstract Chronic administration of synthetic LH-RH (0.5 μg/8 g body weight per day) directly into the graft area in hypophysectomized newts bearing a pituitary autograft results in an increase in testis volume and a recrudescence of spermatogenesis. In two cases round spermatids were formed. In LH-RH-treated animals the graft appears better preserved and richer in type II basophils (presumed gonadotropic cells). The height of the caudal fin (a prolactin-dependent ambisexual character), is more developed in saline-treated than in LH-RH-treated animals.

Steroid hormones in the plasma of the elasmobranch Torpedo marmorata at various stages of the sexual cycle

Abstract Cortisone, cortisol, corticosterone, deoxycorticosterone, testosterone, progesterone, estrone and estriol have been identified in the plasma of female Torpedo marmorata at various stages of the sexual cycle. Details are given about the method, based on thin-layer chromatography followed by gas-liquid chromatography, which has permitted the identification of these steroids.

The effect of synthetic luteinizing hormone releasing hormone on ovulation in the crested new

Abstract Six micrograms of synthetic LH-RH administered by perifusion of the pituitary in situ caused ovulation in winter female newts. A minor effect was obtained through intraperitoneal injection of 24 μg of the hormone. No effect was obtained by means of perifusion of ectopic pituitary autograft or infusion of the hormone into the third ventricle.

Prolactin and Reproduction

In this review we set out to examine the state-of-the-art research into the effects of prolactin (PRL) on various aspects of reproduction in anamniote vertebrates and reptiles. As an introduction, we will examine our knowledge of PRL receptors from a comparative viewpoint (see also Ensor61).