Effect of Melatonin Implants during the Non-Breeding Season on the Onset of Ovarian Activity and the Plasma Prolactin in Dromedary Camel

To examine a possible control of reproductive seasonality by melatonin, continual-release subcutaneous melatonin implants were inserted 4.5 months before the natural breeding season (October–April) into female camels (Melatonin-treated group). The animals were exposed to an artificial long photoperiod (16L:8D) for 41 days prior to implant placement to facilitate receptivity to the short-day signal that is expected with melatonin implants. The treated and control groups (untreated females) were maintained separately under outdoor natural conditions. Ovarian follicular development was monitored in both groups by transrectal ultrasonography and by plasma estradiol-17β concentrations performed weekly for 8 weeks and then for 14 weeks following implant insertion. Plasma prolactin concentrations were determined at 45 and 15 days before and 0, 14, 28, 56, and 98 days after implant insertion. Plasma melatonin concentration was determined to validate response to the artificial long photoperiod and to verify the pattern of release from the implants. Results showed that the artificial long photoperiod induced a melatonin secretion peak of significantly (P < 0.05) shorter duration (about 2.5 h). Melatonin release from the implants resulted in higher circulating plasma melatonin levels during daytime and nighttime which persisted for more than 12 weeks following implants insertion. Treatment with melatonin implants advanced the onset of follicular growth activity by 3.5 months compared to untreated animals. Plasma estradiol-17β increased gradually from the second week after the beginning of treatment to reach significantly (P < 0.01) higher concentrations (39.2 ± 6.2 to 46.4 ± 4.5 pg/ml) between the third and the fifth week post insertion of melatonin implants. Treatment with melatonin implants also induced a moderate, but significant (P < 0.05) suppressive effect on plasma prolactin concentration on the 28th day. These results demonstrate that photoperiod appears to be involved in dromedary reproductive seasonality. Melatonin implants may be a useful tool to manipulate seasonality and to improve reproductive performance in this species. Administration of subcutaneous melatonin implants during the transition period to the breeding season following an artificial signal of long photoperiod have the potential to advance the breeding season in camels by about 2.5 months

Tobacco status, impulsivity, and the five-factor of the PANSS in paranoid schizophrenia

International audienceThere is consistent evidence that impulsivity is linked to tobacco consumption and to symptomatology in schizophrenia. In the current study, we propose a new integrative model of the relationship between impulsivity, psychopathological symptoms, and tobacco status in patients with paranoid schizophrenia. We investigated 33 paranoid schizophrenia patients and 37 healthy controls using a battery of psychopathological scales included the Structured Clinical Interview forDSM-IV(SCID), the five-factor model of the Positive and Negative Symptom Scale (PANSS), the Barratt Impulsiveness Scale (BIS-10), and the UPPS Impulsive Behavior scale (UPPS). Step-wise regression analysis revealed that positive factor of the PANSS and tobacco status contributed positively and significantly to the explained variance of impulsivity. In addition, non-planning impulsivity and sensation-seeking emerged as significant predictors of tobacco status, while smoking predicted non-planning impulsivity and sensation-seeking. Our results suggest that the relationship between sensation-seeking and tobacco use is reciprocal and proposes a new integrative model of the relationship between impulsivity, positive symptoms and tobacco status in patients with paranoid schizophrenia. However, the exact mechanisms for these relationships deserve further investigation