Pineal rhythm of N-acetyltransferase activity and melatonin in the male badger, Meles meles L, under natural daylight: relationship with the photoperiod.

The rhythmicity of melatonin secretion and of pineal NAT activity was compared in male badger kept in natural daylight during two distinctly different photoperiods (January and June). The hormone and its enzyme follow the same pattern with a nighttime elevation and a low level during the day, demonstrating the presence of a nyctohemeral rhythm. The high correlation found between the NAT activity and the melatonin concentration suggests that NAT is the rate-limiting enzyme in melatonin synthesis in the badger. Peak amplitudes were similar under the two photoperiods. Melatonin secretion occurred in the first part of the night irrespective of the photoperiod. The rhythm of melatonin secretion is modified by the photoperiod. The duration of high nighttime levels varies; it is longer (8 h) when the night is long (16 h) in January, and shorter (6 h) when the night is short (8 h) in June. In the badger, differences in the duration of high level melatonin at night may reflect variations in day length and convey to the animal the photoperiodic information.

[LHRH and LH release in the red fox Vulpes vulpes L]. / LHRH et libération de LH chez le Renard roux Vulpes vulpes L.

Pituitary responsiveness to exogenous LHRH was studied in vivo and in vitro in the female red fox, a mono-oestrous species. In vivo, the ability of the pituitary to release LH in response to a single injection of LHRH (2 micrograms/kg) was determined at various stages of the reproductive cycle. The greatest responsiveness is observed during the preovulatory period, the lowest during the luteal phase. During the anoestrus phase, the responsiveness is reduced by more than 50% in lactating females compared to non lactating females. In vitro, dispersed fox anterior pituitary cells were exposed four times to LHRH (10(-9) M), hourly, for 8 min. Pituitary cells were taken from lactating and non lactating females. The cells are not sensitive to LHRH in lactating females but become more and more sensitive after weaning. It is suggested the inhibitory influence of lactation could be the result of prolactin-ovarian steroids-gonadotrophins interactions.

Seasonal variations in plasma luteinizing hormone and testosterone levels in the European badger Meles meles L.

Although active spermatogenesis occurs throughout the year in the male European badger Meles meles L., seasonal fluctuations of testicular activity were observed. The present study compared the pattern of luteinizing hormone (LH) and testosterone (T) secretions throughout the annual cycle. LH secretion was investigated by means of a heterologous radioimmunoassay using anti-ovine LH beta antiserum and canine reference standard. Seasonal and nycthemeral changes in LH and T secretions were observed. During the year a period of maximal values for both hormones is well correlated with the breeding. Moreover, episodic LH releases occurs during the period of minimal testosterone values, indicating resumption of hypothalamo-pituitary activity well before the breeding period.

[Seasonal variations in the sexual activity of the male genet (Genetta genetta L.)]. / Variations saisonnières de l'activité sexuelle de la genette mâle (Genetta genetta L.).

The Genet testis shows a spermatogenic activity throughout the year. The plasmatic androgen level presents two periods where the values are higher; one in spring the other in autumn. The spring testosterone rise coïncides with a mating period.