The objective of this work was to study the effect of small doses of naloxone (Nx) on plasma prolactin (PRL) and testosterone levels, and to correlate hormone changes induced by the opioid antagonist with sexual exhaustion in adult male rabbits. Two groups of 8 adult New Zealand White male rabbits were divided into 2 groups: Group 1 (n=8) was treated with daily intramuscular injections of 0.5 mg of naloxone at 08:00 and at 20:00 hours for 15 days. Group 2 was treated with saline injections. Copulatory behaviour was similar on the first day and during seven days of treatment with Nx in both groups; mounts and copulations averaged 8.1 to 7.21. After 15 days of treatment with Nx, a significant increase in mount/copulation events was observed in naloxone treated rabbits as compared with controls (11.1 vs 7.6) (P<0.001). Mounts and copulations in the Nx treated rabbits was significantly higher than control rabbits (P<0.001) (9.4 vs 7.6) seven days after treatment with Nx was discontinued. During the first week of treatment, plasma testosterone levels in Nx treated rabbits were similar to those of the control group. At the end of the first week of treatment with Nx, there was a continuous increase in testosterone levels and high levels of the androgen were still detectable seven days after naloxone treatment was discontinued. There was a significant overall effect of treatment (P<0.001). It was concluded that endogenous opioids are important modulators of sexual behaviour in rabbits

Ewe sexual preference depends on several factors; ram attractiveness is important. This work was carried out in in the first week of September 2020 and repeated in November 2021. For the first trial two rams were treated with 0.5 mg naloxone im for 15 days, two control rams were treated with saline injections. Sexual preference was studied with synchronized ewes (n 0 12) displaying estrus at the end of naloxone treatment of the rams. Ewe’s proceptive and receptive behavior were noted. Plasma testosterone levels were monitored through the duration of the experiment in treated and control rams. For the second trial 4 rams and ewes were treated same as trial 1, and the number of ewes was increased to 24. It was observed that on the first week of treatment, testosterone levels were not significantly different between treated and control rams; but at the beginning of the second week of treatment testosterone plasma levels in naloxone treated rams increased until values reached levels of 15 ng/mL compared with 6 ng/mL in control rams. When ewes were exposed to treated and untreated rams during the first trial, 11 ewes showed high proceptivity and receptivity for the naloxone treated ram (p<0.01) and they were mated, for the control ram only one ewe showed complete preference. In the second trial it was observed that 19 ewes also showed high proceptivity and receptivity for naloxone treated rams (p < .001). Hormone levels behaved following the same pattern as that observed during the first trial. It was concluded that naloxone treatment facilitated the secretion of testosterone in rams and the high concentration of this androgen motivated ewes to prefer mating with the naloxone treated ram.

In a quarter-mile horse, a tumor-like mass was presented on the left flank, with a diagnosis of sarcoid. At the beginning, cures were carried out twice a day with natural water, hydrogen peroxide and coumaphos with propoxur as mosquicide and larvicide, observing that there was no favorable regeneration of the tissue and after the surgical removal of the tumoral mass. Treatment with NANOCIT was initiated on the 16th after surgery, a spray with citrus extracts adsorbed to a titanium nanoparticles (NANOCIT) at 12 hours intervals for 15 days, treatment wit NANOCIT promoted an abundant granulation tissue with a termination of the inflammatory process with good cicatrization.

Se discute la interacción de los opioides endógenos con la reproducción en bovinos y los experimentos previos para relacionar las endorfinas con la secreción de LH y FSH a nivel Hipotalámico. Se discute el uso de antagonistas opioides para estudiar la interacción de las endorfinas con la secreción de gonadotrofinas. Se discute el uso de antagonistas opioides en diferentes dosis. Se hace énfasis en la presencia de diferentes receptores opioides endógenos y su interacción con antagonistas opioides en función de la dosis administrada. Se discute el uso de pequeñas dosis de antagonistas opioides para de manera selectiva interferir con receptores endógenos micro, relacionados íntimamente con su función sobre la secreción de GnRH hipotalámica, efecto que permite contemplar el uso de antagonistas opioides para el tratamiento de quistes foliculares en vacas repetidoras.