Efficacy and safety of halo-gravity traction in the treatment of spinal deformities: A systematic review of the literature / Eficacia y seguridad de la tracción de halo-gravedad en el tratamiento de las deformidades de columna: una revisión sistemática de la literatura

Objective: To determine, through a systematic review, the effects of halo gravity traction in spinal deformity. Methods: Prospective studies or case series of patients with scoliosis or kyphosis treated with cranial halo gravity traction (HGT) were included. Radiological outcomes were measured in the sagittal and/or coronal planes. Pulmonary function was also assessed. Perioperative complications were also collected. Results: Thirteen studies were included. Congenital etiology was the most frequent etiology observed. Most studies provided clinically relevant curve correction values in the sagittal and coronal planes. Pulmonary values improved significantly after the use of HGT. Finally, there were a pool of 83 complications in 356 patients (23.3%). The most frequent complications were screw infection (38 cases). Conclusions: Preoperative HGT appears to be a safe and effective intervention for deformity that allows correction prior to surgery. However, there is a lack of homogeneity in the published studies.(AU)

Objetivo: Determinar, mediante una revisión sistemática, los efectos de la tracción de halo-gravedad (HGT) en las deformidades de columna. Métodos: Se incluyeron estudios prospectivos o series de casos de pacientes con escoliosis o cifosis tratados con HGT. Los resultados radiológicos se midieron en los planos sagital y/o coronal. También se evaluó la función pulmonar. Finalmente, se recogieron las complicaciones perioperatorias. Resultados: Se incluyeron 13 estudios. La etiología congénita fue la más frecuente. La mayoría de los estudios proporcionaron valores de corrección de la curva clínicamente relevantes en los planos sagital y coronal. Los valores pulmonares mejoraron significativamente tras el uso de HGT. Por último, existieron 83 complicaciones en 356 pacientes, siendo la infección la más frecuente (38 casos). Conclusiones: La HGT mostró ser una intervención segura y eficaz para la deformidad, que permite la corrección antes de la cirugía. Sin embargo, existe una falta de homogeneidad en los estudios publicados.(AU)

[Artículo traducido] Eficacia y seguridad de la tracción de halo-gravedad en el tratamiento de las deformidades de columna: una revisión sistemática de la literatura / Efficacy and safety of halo-gravity traction in the treatment of spinal deformities: A systematic review of the literature

Objective: To determine, through a systematic review, the effects of halo gravity traction in spinal deformity. Methods: Prospective studies or case series of patients with scoliosis or kyphosis treated with cranial halo gravity traction (HGT) were included. Radiological outcomes were measured in the sagittal and/or coronal planes. Pulmonary function was also assessed. Perioperative complications were also collected. Results: Thirteen studies were included. Congenital etiology was the most frequent etiology observed. Most studies provided clinically relevant curve correction values in the sagittal and coronal planes. Pulmonary values improved significantly after the use of HGT. Finally, there were a pool of 83 complications in 356 patients (23.3%). The most frequent complications were screw infection (38 cases). Conclusions: Preoperative HGT appears to be a safe and effective intervention for deformity that allows correction prior to surgery. However, there is a lack of homogeneity in the published studies.(AU)

Objetivo: Determinar, mediante una revisión sistemática, los efectos de la tracción de halo-gravedad (HGT) en las deformidades de columna. Métodos: Se incluyeron estudios prospectivos o series de casos de pacientes con escoliosis o cifosis tratados con HGT. Los resultados radiológicos se midieron en los planos sagital y/o coronal. También se evaluó la función pulmonar. Finalmente, se recogieron las complicaciones perioperatorias. Resultados: Se incluyeron 13 estudios. La etiología congénita fue la más frecuente. La mayoría de los estudios proporcionaron valores de corrección de la curva clínicamente relevantes en los planos sagital y coronal. Los valores pulmonares mejoraron significativamente tras el uso de HGT. Por último, existieron 83 complicaciones en 356 pacientes, siendo la infección la más frecuente (38 casos). Conclusiones: La HGT mostró ser una intervención segura y eficaz para la deformidad, que permite la corrección antes de la cirugía. Sin embargo, existe una falta de homogeneidad en los estudios publicados.(AU)

Retorno a la actividad completa tras cirugía de reconstrucción de ligamento cruzado anterior en personal militar: metaanálisis / Return to full duty after anterior cruciate ligament reconstruction surgery in military personnel: A meta-analysis

Objetivo: Se realizó un metaanálisis para evaluar los resultados clínico-funcionales de la cirugía de ligamento cruzado anterior en militares, así como las complicaciones asociadas a la misma. Material y métodos: Se realizó una búsqueda en las 3 principales fuentes de bases de datos hasta diciembre de 2022 (PubMed, Google Scholar y ScienceDirect) en cuanto a los resultados tras la cirugía de ligamento cruzado anterior en personal militar. La revisión sistemática se realizó siguiendo las normas Preferred Reporting Items for Systematic Reviews and Meta-Analyses –PRISMA–, y los criterios de inclusión siguieron la estrategia PICO. Los datos de los estudios incluidos se analizaron mediante el software Review Manager 5.4. Resultados: Se seleccionaron un total de 7 estudios retrospectivos. La tasa general de retorno a la actividad completa en el personal militar fue del 62,3% (61,5% para el grupo de no oficiales frente a 68,3% para el grupo de oficiales), sin ser esta diferencia significativa (p=0,92). La tasa general de lesión meniscal en los militares fue del 58,8%, sin ser esta diferencia significativa (p=0,88). La homogeneidad en ambos casos fue buena (I2=0%, p=0,99). Conclusión: El regreso a la actividad militar completa puede usarse en la población militar como un marcador de éxito después de una reconstrucción de ligamento cruzado anterior. Hay que destacar que una gran cantidad de militares experimentan limitaciones permanentes en la actividad que impiden el regreso completo al servicio.(AU)

Objective: A meta-analysis was carried out to evaluate the clinical-functional results of anterior cruciate ligament surgery in military population, as well as the complications associated with it. Material and method: Three major database sources up to December 2022 (PubMed, Google Scholar, and ScienceDirect) were searched for outcomes after anterior cruciate ligament surgery in military personnel. The systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses –PRISMA– standards, and the inclusion criteria following the PICO strategy. Data from included studies were analyzed using Review Manager 5.4 software. Results: A total of 7 retrospective studies were selected. The general rate of return to full duty in military personnel was 62.3% (61.5% for the non-officer group vs. 68.3% for the officer group) without this difference being significant (p=0.92). The general rate of meniscal injury in the military was 58.8%, without this difference being significant (p=0.88). The homogeneity in both cases was good (I2=0%, p=0.99). Conclusion: Return to full military duty can be used in the military population as a marker of success after anterior cruciate ligament reconstruction. It should be noted that a large number of military personnel experience permanent activity limitations that prevent full return to service.(AU)

[Translated article] Return to full duty after anterior cruciate ligament reconstruction surgery in military personnel: A meta-analysis / Retorno a la actividad completa tras cirugía de reconstrucción del ligamento cruzado anterior en personal militar: metaanálisis

Objetivo: Se realizó un metaanálisis para evaluar los resultados clínico-funcionales de la cirugía de ligamento cruzado anterior en militares, así como las complicaciones asociadas a la misma. Material y métodos: Se realizó una búsqueda en las 3 principales fuentes de bases de datos hasta diciembre de 2022 (PubMed, Google Scholar y ScienceDirect) en cuanto a los resultados tras la cirugía de ligamento cruzado anterior en personal militar. La revisión sistemática se realizó siguiendo las normas Preferred Reporting Items for Systematic Reviews and Meta-Analyses –PRISMA–, y los criterios de inclusión siguieron la estrategia PICO. Los datos de los estudios incluidos se analizaron mediante el software Review Manager 5.4. Resultados: Se seleccionaron un total de 7 estudios retrospectivos. La tasa general de retorno a la actividad completa en el personal militar fue del 62,3% (61,5% para el grupo de no oficiales frente a 68,3% para el grupo de oficiales), sin ser esta diferencia significativa (p=0,92). La tasa general de lesión meniscal en los militares fue del 58,8%, sin ser esta diferencia significativa (p=0,88). La homogeneidad en ambos casos fue buena (I2=0%, p=0,99). Conclusión: El regreso a la actividad militar completa puede usarse en la población militar como un marcador de éxito después de una reconstrucción de ligamento cruzado anterior. Hay que destacar que una gran cantidad de militares experimentan limitaciones permanentes en la actividad que impiden el regreso completo al servicio.(AU)

Objective: A meta-analysis was carried out to evaluate the clinical-functional results of anterior cruciate ligament surgery in military population, as well as the complications associated with it. Material and method: Three major database sources up to December 2022 (PubMed, Google Scholar, and ScienceDirect) were searched for outcomes after anterior cruciate ligament surgery in military personnel. The systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses –PRISMA– standards, and the inclusion criteria following the PICO strategy. Data from included studies were analyzed using Review Manager 5.4 software. Results: A total of 7 retrospective studies were selected. The general rate of return to full duty in military personnel was 62.3% (61.5% for the non-officer group vs. 68.3% for the officer group) without this difference being significant (p=0.92). The general rate of meniscal injury in the military was 58.8%, without this difference being significant (p=0.88). The homogeneity in both cases was good (I2=0%, p=0.99). Conclusion: Return to full military duty can be used in the military population as a marker of success after anterior cruciate ligament reconstruction. It should be noted that a large number of military personnel experience permanent activity limitations that prevent full return to service.(AU)

Short versus long intramedullary nails for intertrochanteric hip fracture: Meta-analysis. / [Artículo traducido] Clavo corto versus clavo largo en la fractura intertrocantérica de cadera: metaanálisis.

OBJECTIVE: To compare short versus long intramedullary nails for intertrochanteric hip fractures in terms of efficacy and safety. METHODS: We included cohort studies and randomized clinical trials. The methodological quality of the studies was assessed by the Newcastle-Ottawa Scale. The meta-analysis was performed using the Review Manager 5.4. Heterogeneity was checked with the I2 test. A fixed effects model was adopted if there was no heterogeneity. RESULTS: Twelve studies were included. The reoperations rate was lower in the short nail group (OR: 0.58, 95%CI: 0.38-0.88) and there were no differences regarding the peri-implant fracture rate (OR: 1.77, 95%CI: 0.68-4.60). Surgery time and blood loss was significantly higher in the long nail group (MD: -12.44, 95%CI: -14.60 -10.28) (MD: -19.36, 95%CI: -27.24 -11.48). There were no differences in functional outcomes. CONCLUSIONS: The long nail showed a higher reoperation rate, blood loss and surgery time compared to the short nail. LEVEL OF EVIDENCE: III.

[Translated article] Return to full duty after anterior cruciate ligament reconstruction surgery in military personnel: A meta-analysis.

OBJECTIVE: A meta-analysis was carried out to evaluate the clinical-functional results of anterior cruciate ligament surgery in military population, as well as the complications associated with it. MATERIAL AND METHOD: Three major database sources up to December 2022 (PubMed, Google Scholar, and ScienceDirect) were searched for outcomes after anterior cruciate ligament surgery in military personnel. The systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses -PRISMA- standards, and the inclusion criteria following the PICO strategy. Data from included studies were analysed using Review Manager 5.4 software. RESULTS: A total of seven retrospective studies were selected. The general rate of return to full duty in military personnel was 62.3% (61.5% for the non-officer group versus 68.3% for the officer group) without this difference being significant (p=0.92). The general rate of meniscal injury in the military was 58.8%, without this difference being significant (p=0.88). The homogeneity in both cases was good (I2=0%, p=0.99). CONCLUSION: Return to full military duty can be used in the military population as a marker of success after anterior cruciate ligament reconstruction. It should be noted that a large number of military personnel experience permanent activity limitations that prevent full return to service.

Return to full duty after anterior cruciate ligament reconstruction surgery in military personnel: A meta-analysis. / Retorno a la actividad completa tras cirugía de reconstrucción de ligamento cruzado anterior en personal militar: metaanálisis.

OBJECTIVE: A meta-analysis was carried out to evaluate the clinical-functional results of anterior cruciate ligament surgery in military population, as well as the complications associated with it. MATERIAL AND METHOD: Three major database sources up to December 2022 (PubMed, Google Scholar, and ScienceDirect) were searched for outcomes after anterior cruciate ligament surgery in military personnel. The systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses -PRISMA- standards, and the inclusion criteria following the PICO strategy. Data from included studies were analyzed using Review Manager 5.4 software. RESULTS: A total of 7 retrospective studies were selected. The general rate of return to full duty in military personnel was 62.3% (61.5% for the non-officer group vs. 68.3% for the officer group) without this difference being significant (p=0.92). The general rate of meniscal injury in the military was 58.8%, without this difference being significant (p=0.88). The homogeneity in both cases was good (I2=0%, p=0.99). CONCLUSION: Return to full military duty can be used in the military population as a marker of success after anterior cruciate ligament reconstruction. It should be noted that a large number of military personnel experience permanent activity limitations that prevent full return to service.

The Impact of Hypoalbuminemia on Postoperative Complications in Patients Undergoing Shoulder Arthroplasty: A Meta-Analysis.

OBJECTIVES: The objective of this meta-analysis was to investigate the association between hypoalbuminemia and postoperative complications in patients undergoing shoulder arthroplasty. METHODS: This meta-analysis study was registered in PROSPERO (CRD42023442466) and adhered to the PRISMA guidelines. Studies focused on shoulder arthroplasty that compared hypoalbuminemia and normal albumin levels were included. A systematic literature search was conducted in PubMed, EMBASE, Scopus, and the Cochrane Collaboration database. Seven comparative studies were included, and odds ratios with a 95% confidence interval were calculated for the dichotomous variables. A fixed-effect model was used when there was no statistical evidence of heterogeneity, and a random-effect model was used when significant heterogeneity was observed. Review Manager 5.4 software was used for data analysis. RESULTS: The meta-analysis included a total of 20,290 patients from seven studies. Hypoalbuminemia was significantly associated with a higher risk of readmissions (OR 2.92, 95%CI 1.74 to 4.91), reoperations (OR 3.23, 95%CI 1.98 to 5.27), an increase in hospital stay duration (MD 1.59, 95%CI 0.86 to 2.32), and complications such as death (OR 5.75, 95% CI 2.98 to 11.08; studies = 4), thromboembolic events (OR 2.43, 95% CI 1.46 to 4.06; studies = 4), cardiac events (OR 2.78, 95% CI 1.07 to 7.24; studies = 3), pulmonary infections (OR 3.09, 95% CI 1.54 to 6.20; studies = 3), systemic infections (OR 2.19, 95% CI 1.51 to 3.16; studies = 3), and transfusions (OR 3.16, 95% CI 2.23 to 4.48; studies = 2). However, there was no significant association between hypoalbuminemia and renal complications, surgical site infections, urinary tract infections, wound problems, or cardiovascular events. CONCLUSION: This meta-analysis provides strong evidence that hypoalbuminemia is associated with a higher risk of postoperative complications in patients undergoing shoulder arthroplasty.

Does vitamin D deficiency affect functional outcomes in hip fracture patients? A meta-analysis of cohort studies.

BACKGROUND: Vitamin D deficiency is common in patients with hip fractures and may negatively affect functional recovery and quality of life (QOL). OBJECTIVE: This study aimed to conduct a meta-analysis to quantify the effects of vitamin D deficiency on physical function and quality of life after hip fractures. METHODS: The PubMed, EMBASE, Scopus, and Cochrane Library databases were searched for relevant studies. The inclusion criteria were hip fracture, comparison between vitamin D deficiency and normal vitamin D levels in patients with hip fracture, and functional outcome as the primary outcome. The exclusion criteria were case reports, reviews, duplicates, studies with a high risk of bias, and non-comparable or missing data. Two independent reviewers selected studies, extracted data, assessed bias, and performed meta-analyses using the Review Manager. Heterogeneity and publication bias were also assessed. Two independent reviewers selected the studies, extracted data, and assessed the risk of bias. We performed a meta-analysis using Review Manager and assessed heterogeneity and publication bias. RESULTS: Seven studies with 1,972 patients were included. Vitamin D deficiency was defined as a 25(OH)D level < 20 ng/mL. There were no significant differences in the ability to walk (OR 0.68, 95% CI 0.31-1.53, I2 = 69%) or length of hospital stay (MD 2.27 days, 95% CI - 2.47 to 7.01, I2 = 93%) between patients with and without vitamin D deficiency. However, patients with vitamin D deficiency had significantly worse functional ability and quality of life (SMD - 1.50, 95% CI - 2.88 to - 0.12, I2 = 96%). CONCLUSIONS: Despite the limitations of this study, such as small sample size, heterogeneous outcome assessments, and variable vitamin D measurement techniques, the results demonstrated that screening for vitamin D status and optimizing levels through supplementation could facilitate rehabilitation, promote lifestyle changes, aid in the recovery of independence, and help reduce long-term burdens.

Efficacy and safety of halo-gravity traction in the treatment of spinal deformities: A systematic review of the literature. / [Artículo traducido] Eficacia y seguridad de la tracción de halo-gravedad en el tratamiento de las deformidades de columna: una revisión sistemática de la literatura.

OBJECTIVE: To determine, through a systematic review, the effects of halo-gravity traction (HGT) in spinal deformity. METHODS: Prospective studies or case series of patients with scoliosis or kyphosis treated with cranial HGT were included. Radiological outcomes were measured in the sagittal and/or coronal planes. Pulmonary function was also assessed. Perioperative complications were also collected. RESULTS: Thirteen studies were included. Congenital etiology was the most frequent etiology observed. Most studies provided clinically relevant curve correction values in the sagittal and coronal planes. Pulmonary values improved significantly after the use of HGT. Finally, there were a pool of 83 complications in 356 patients (23.3%). The most frequent complications were screw infection (38 cases). CONCLUSIONS: Preoperative HGT appears to be a safe and effective intervention for deformity that allows correction prior to surgery. However, there is a lack of homogeneity in the published studies.

Short versus long intramedullary nails for intertrochanteric hip fracture: Meta-analysis.

OBJECTIVE: To compare short versus long intramedullary nails for intertrochanteric hip fractures in terms of efficacy and safety. METHODS: We included cohort studies and randomized clinical trials. The methodological quality of the studies was assessed by the Newcastle-Ottawa Scale. The meta-analysis was performed using the Review Manager 5.4. Heterogeneity was checked with the I2 test. A fixed effects model was adopted if there was no heterogeneity. RESULTS: Twelve studies were included. The reoperations rate was lower in the short nail group (OR 0.58, 95% CI 0.38-0.88) and there were no differences regarding the peri-implant fracture rate (OR 1.77, 95% CI 0.68-4.60). Surgery time and blood loss was significantly higher in the long nail group (MD -12.44, 95% CI -14.60 to (-10.28)) (MD -19.36, 95% CI -27.24 to (-11.48)). There were no differences in functional outcomes. CONCLUSIONS: The long nail showed a higher reoperation rate, blood loss and surgery time compared to the short nail.

Efficacy and safety of halo-gravity traction in the treatment of spinal deformities: A systematic review of the literature.

OBJECTIVE: To determine, through a systematic review, the effects of halo gravity traction in spinal deformity. METHODS: Prospective studies or case series of patients with scoliosis or kyphosis treated with cranial halo gravity traction (HGT) were included. Radiological outcomes were measured in the sagittal and/or coronal planes. Pulmonary function was also assessed. Perioperative complications were also collected. RESULTS: Thirteen studies were included. Congenital etiology was the most frequent etiology observed. Most studies provided clinically relevant curve correction values in the sagittal and coronal planes. Pulmonary values improved significantly after the use of HGT. Finally, there were a pool of 83 complications in 356 patients (23.3%). The most frequent complications were screw infection (38 cases). CONCLUSIONS: Preoperative HGT appears to be a safe and effective intervention for deformity that allows correction prior to surgery. However, there is a lack of homogeneity in the published studies.

Mothers and offspring: The rabbit as a model system in the study of mammalian maternal behavior and sibling interactions.

UNLABELLED: This article is part of a Special Issue "Parental Care". Jay Rosenblatt effectively promoted research on rabbit maternal behavior through his interaction with colleagues in Mexico. Here we review the activities of pregnant and lactating rabbits (Oryctolagus cuniculus), their neuro-hormonal regulation, and the synchronization of behavior between mother and kits. Changing concentrations of estradiol, progesterone, and prolactin throughout gestation regulate nest-building (digging, straw-carrying, fur-pulling) and prime the mother's brain to respond to the newborn. Nursing is the only mother-young contact throughout lactation. It happens once/day, inside the nest, with ca. 24h periodicity, and lasts around 3min. Periodicity and duration of nursing depend on a threshold of suckling as procedures reducing the amount of nipple stimulation interfere with the temporal aspects of nursing, though not with the doe's maternal motivation. Synchronization between mother and kits, critical for nursing, relies on: a) the production of pheromonal cues which guide the young to the mother's nipples for suckling; b) an endogenous circadian rhythm of anticipatory activity in the young, present since birth. Milk intake entrains the kits' locomotor behavior, corticosterone secretion, and the activity of several brain structures. Sibling interactions within the huddle, largely determined by body mass at birth, are important for: a) maintaining body temperature; b) ensuring normal neuromotor and social development. Suckling maintains nursing behavior past the period of abundant milk production but abrupt and efficient weaning occurs in concurrently pregnant-lactating does by unknown factors. CONCLUSION: female rabbits have evolved a reproductive strategy largely dissociating maternal care from maternal presence, whose multifactorial regulation warrants future investigations.

Ovarian hormones and fasting differentially regulate pituitary receptors for estrogen and gonadotropin-releasing hormone in rabbit female.

To investigate the mechanisms by which caloric restriction affects reproductive function in female rabbits, we measured, in animals intact or ovariectomized (OVX) estrogen-primed and fed ad libitum or fasted for 48 h, the adenohypophysial expression of estrogen receptor-alpha (ESR1) and gonadotropin releasing hormone receptor (GnRHR) and the dynamic secretion of LH following GnRH stimulation. Fasting increased the number of GnRHR-immunoreactive (-IR) cells in intact animals, whereas reduced the density of ESR1-IR cells in OVX rabbits. Estrogen priming decreased the number of ESR1-IR cells in fasted and OVX animals. Ovariectomy increased the number of ESR1-IR cells in fed rabbits, but caused an opposite effect in both fed and fasted animals treated with estrogen. Fasting down regulated the mRNA levels for ESR1 and GnRHR. Estrogen-priming reduced the abundance for ESR1 mRNA in both fed and fasted rabbits, and that for GnRHR in fasted rabbits. Ovariectomy halved ESR1 mRNA levels independently of treatment and feeding condition, whereas increased (P < 001) that for GnRHR in estrogen-primed rabbits. In all rabbits, an LH surge occurred 30 min after GnRH injection but the lowest levels were found in intact fasted rabbits and the highest in fasted, estrogen-primed animals. The LH profile was similar in intact and OVX rabbits and neither fasting nor estrogen priming modified it. In conclusion, fasting differentially modifies the ESR1 and GnRHR expression in the pituitary, depending on the presence of gonadal hormones, indicating complex interactions between metabolic signals and ovarian steroids.

Expression of the cannabinoid receptor type 1 in the pituitary of rabbits and its role in the control of LH secretion.

The aim of this study was to elucidate the possible direct regulatory role of the endocannabinoids in the modulation of LH secretion in rabbits, a reflex ovulator species. The cannabinoid receptor type 1 (CB1) was characterized by RT-PCR techniques in the anterior pituitary of intact and ovariectomized does treated with GnRH and primed with estrogen and CB1 antagonist, rimonabant. Cannabinoid receptor type 1 immune reaction was evidenced by immunohistochemistry in the cytoplasm of approximately 10% of the pituitary cells with a density of 8.5 ± 1.9 (per 0.01 mm(2)), both periodic acid-Schiff positive (30%) and negative (70%). All CB1-immunoreactive cells were also immune reactive for estrogen receptor type 1. Ovariectomy, either alone or combined with estrogen priming, did not modify the relative abundances of pituitary CB1 mRNA, but decreased (P < 0.01) the expression of estrogen receptor type 1 mRNA. Treatment with CB1 antagonist (rimonabant) inhibited (P < 0.01) LH secretory capacity by the pituitary after GnRH injection, and estrogen priming had no effect. The present findings indicate that the endocannabinoid system is a potential candidate for the regulation of the hypothalamic-pituitary-ovarian axis in reflex ovulatory species.

Relevance of ovarian signaling for the early behavioral transition from estrus to pregnancy in the female rabbit.

During estrus, the female domestic rabbit (Oryctolagus cuniculus) displays scent marking behavior (chinning), which is immediately inhibited after mating, temporarily recovers, and then declines and remains inhibited across pregnancy. Chinning is inhibited by progesterone (P) and the activation of the progesterone receptor (PR), but it is unlikely that P participates in the "acute" (immediate) or "early" inhibition of chinning (24 to 96 h post-mating, before plasma P levels rise). Since PR is activated in a ligand-independent manner by a variety of signaling molecules, some of which (e.g., GnRH) are also associated with reflexive ovulation in this species, we hypothesized that neurochemical/neuroendocrine signals associated with mating activate PR, resulting in the inhibition of chinning. In Experiment 1, we tested whether the PR antagonist, RU486 (20 mg, injected s.c. at -1 h, or at -7 h and +3 h relative to mating) prevented the post-mating inhibition of chinning in intact females. RU486 did not prevent the post-mating decline in chinning, indicating that PR activation associated with mating is not necessary for this effect. In Experiment 2, we used ovariectomized (OVX), estradiol benzoate (EB)-treated females to test the hypothesis that ovarian signaling is necessary for the post-mating inhibition of chinning. The acute inhibition of chinning occurred in OVX females, but the early inhibition was absent. We conclude that ovarian signaling is necessary for the early, but not acute, post-mating inhibition of chinning. The PR seems not to participate in either of these phases.

Maternal care of rabbits in the lab and on the farm: endocrine regulation of behavior and productivity.

Maternal behavior in rabbits has been well described in the wild, the laboratory, and the farm. Salient characteristics include: (a) the construction of a nest (inside an underground burrow or a box), composed of straw/grass and body hair and (b) the display of a single, brief (ca. 3 min) nursing bout per day. The onset and decline of nest-building in mid and late pregnancy are controlled by specific combinations of estradiol, progesterone, testosterone, and prolactin. Following parturition (kindling) does can mate and become pregnant again. Management strategies have been used on the farm to enhance productivity, impinging on specific reproductive processes (e.g., use of hormones to synchronize estrus, artificial insemination at kindling, doe-litter separation on specific days of lactation to increase sexual receptivity and fertility). Knowledge about the rabbit's reproductive physiology and behavior will be enriched by integrating research coming from the laboratory (where estrus, pregnant-only, or lactating-only animals are the main categories investigated) with studies performed on the farm or research station (where pregnant-lactating rabbits are prevalent). Similarly, the high productivity demands of modern rabbit farms will benefit from the information obtained in the laboratory where specific issues in reproductive neuroendocrinology are explored with methodologies that are not amenable for farm use.

Progesterone receptor activation signals behavioral transitions across the reproductive cycle of the female rabbit.

The female rabbit is an exceptional experimental model to define mechanisms by which progesterone (P) controls the expression of reproductive behaviors. In the rabbit, the rise in P levels during pregnancy inhibits estrous scent marking ("chinning"), stimulates the excavation of a nest burrow ("digging"), and primes behaviors later used for nest construction. The pre-parturient fall of P triggers the construction of a straw nest ("straw carrying") that is lined with hair that she pulls from her own body ("hair pulling"). These behaviors can be replicated in ovariectomized (ovx) females given a schedule of estradiol (E) and P that mimics hormone levels during pregnancy (E from days 0 to 4, E + P from days 5 to 17, E from days 18 to 27). We administered PR antagonists RU486 or CDB(VA)2914 to ovx female rabbits during either the initial (days 5-11) or late (days 12-17) phases of P treatment, to determine the role of PR activation in coordinating the expression of these behaviors. Both antiprogestins attenuated the P-mediated decline in chinning and increase in digging when administered during days 5-11. When given across days 12-17, both antiprogestins triggered an early decline in digging, the onset of nest building in some Ss, and the reinstatement of chinning. These results point to a central role of PR activation for establishing and maintaining the behavioral phenotype of pregnancy, and for the behavioral transition from pregnancy to estrus.

Intracerebroventricular injections of prolactin counteract the antagonistic effect of bromocriptine on rabbit maternal behaviour.

To investigate the participation of prolactin in nest-building and maternal behaviour in rabbits, we administered (from pregnancy day 26 to parturition) rabbit prolactin (rbPRL; or vehicle) intracerebroventricularly (i.c.v.) to primiparous animals injected with bromocriptine subcutaneously (s.c.). Control females (given vehicle s.c. and i.c.v.) built a maternal nest (of straw and body hair) in 77% of cases. This proportion decreased to 19% in the bromocriptine-only group (P < 0.05) and increased to 93% in the group given bromocriptine plus rbPRL (P > 0.05). Maternal behaviour (i.e. the adoption of a crouching posture over the litter inside the nest box) was expressed by 77% of control rabbits, 19% of bromocriptine-only animals (P < 0.05) and 57% of females given bromocriptine plus rbPRL (P > 0.05). Values of nonmaternal activities (i.e. scent-marking, ambulation in an open field) were similar among the three studied groups. These results suggest that prolactin, acting in late pregnancy, plays a major role in the stimulation of nest-building and maternal behaviour in rabbits.

Non-ligand activation of estrous behavior in rodents: cross-talk at the progesterone receptor.

Estrous behavior in rodents is triggered by the binding of progesterone (P) to its intracellular receptor (PR). Non-steroidal agents (i.e., gonadotropin-releasing hormone, noradrenaline, dopamine and others), acting at the membrane, can facilitate estrous behavior in estrogen-primed rats. This action is mediated through the generation of second messengers (cyclic AMP, cyclic GMP, calcium) which, in turn, phosphorylate through diverse kinase systems (protein kinases A, G or C) either the PR or associated effector proteins linking the PR to the trans-activation machinery. P or its metabolites also activate cyclic AMP-signaling pathways by acting directly on the membrane or by modulating neurotransmitter release. Molecular processes resulting from second messenger signaling pathways and those from the progesterone-RP interaction synergize to elicit a full behavioral response.