Effect of gonadectomy on subsequent development of age-related cognitive impairment in dogs

A role for GnRH in olfaction and cognition: Implications for veterinary medicine

Pulsatile secretion of gonadotropin-releasing hormone (GnRH) is essential for the activation and maintenance of the function of the hypothalamic-pituitary-gonadal (HPG) axis, which controls the onset of puberty and fertility. Two provocative recent studies suggest that, in addition to control reproduction, the neurons in the brain that produce GnRH are also involved in the control postnatal brain maturation, odour discrimination and adult cognition. Long-acting GnRH antagonists and agonists are commonly used to control fertility and behaviour in veterinary medicine, primarily in males. This review puts into perspective the potential risks of these androgen deprivation therapies and immunization on olfactory and cognitive performances and well-aging in domestic animals, including pets. We will also discuss the results reporting beneficial effects of pharmacological interventions restoring physiological GnRH levels on olfactory and cognitive alterations in preclinical models of Alzheimer's disease, which shares many pathophysiological and behavioural hallmarks with canine cognitive dysfunction. These novel findings raise the intriguing possibility that pulsatile GnRH therapy holds therapeutic potential for the management of this behavioural syndrome affecting older dogs.

Inguinal Hernia in Nonhuman Primates: From Asymptomatic to Life-Threatening Events

In this study, a review of available data and literature on the epidemiology and anamnesis of inguinal hernias in nonhuman primates, as well as on their clinical evaluation and surgical management, was conducted. Inguinal hernias are assumed to be relatively common in male nonhuman primates. Clinical signs are usually limited to a visible or palpable mass in the groin region without pain or systemic illness. Most hernias contain omentum. Careful monitoring is an acceptable treatment option for those animals. Size, the danger of incarceration, and the presence of strangulation are important factors when considering surgical repair. A strangulated inguinal hernia is an emergency, requiring prompt surgery to avoid tissue necrosis and death. Imaging techniques, as well as computed tomography (CT), ultrasonography, and magnetic resonance imaging (MRI), provide information about the anatomical characteristics of the suspected region, allowing for a diagnosis and treatment. An inguinal hernia repair can be performed with either open surgery or laparoscopic surgery. The hernia repair can be achieved by mesh or suture. Decisions regarding which repair technique to use depend on the surgeon′s skill level and preference. Complication and recurrence rates are generally low. The most common postsurgical complication is a recurrence of the hernia. Contraceptive measures are not indicated in breeders, as there is no known hereditary component, and the presence of hernia does not appear to affect fertility, nor does it predispose to occurrence, recurrence, or incarceration.

Nutrients, Cognitive Function, and Brain Aging: What We Have Learned from Dogs

Due to a difference in genetics, environmental factors, and nutrition, just like in people, dogs age at different rates. Brain aging in people and dogs share similar morphological changes including irreversible cortical atrophy, cerebral amyloid angiopathy, and ventricular enlargement. Due to severe and irreversible brain atrophy, some aging dogs develop cognitive dysfunction syndrome (CDS), which is equivalent to dementia or Alzheimer’s disease (AD) in people. The risk factors and causes of CDS in dogs have not been fully investigated, but age, gender, oxidative stress, and deficiency of sex hormones appears to be associated with increased risk of accelerated brain aging and CDS in dogs. Both AD and CDS are incurable diseases at this moment, therefore more efforts should be focused on preventing or reducing brain atrophy and minimizing the risk of AD in people and CDS in dogs. Since brain atrophy leads to irreversible cognitive decline and dementia, an optimal nutritional solution should be able to not only enhance cognitive function during aging but also reduce irreversible brain atrophy. Up to now, only one nutritional intervention has demonstrated both cognition-enhancing benefits and atrophy-reducing benefits.

An Ancient Practice but a New Paradigm: Personal Choice for the Age to Spay or Neuter a Dog

Extensive practice and knowledge of the methods and effects of castration of male livestock and even humans has been widespread since ancient times, but only a few decades ago did neutering (including spaying) become a routine part of canine husbandry. In the US, the 6-month neuter became standard practice. Only recently, however, have some of the consequences of this major physiological alteration become evident. As the data-based study on 35 breeds reveals, there are major breed differences associated with effects of neutering, especially with early neutering, including increased risks of joint disorders and some cancers. The study of mixed-breed dogs reveals that the risk of joint disorders is increased in the large dogs. Implications of breed-specific and sex-specific effects for age of neutering have prompted the consideration of a new paradigm with regard to this practice. This involves focusing on each individual dog when deciding upon the appropriate age of neutering to avoid increasing the risk of a joint disorder or cancer above that inherent for the breed. For many breeds, particularly the smaller dogs, no effects were found for the age of neutering on joint disorders and the cancers followed. In these cases, the caregiver has a wide range of choice for neutering without increasing the dog's risk for these diseases. In the future, additional research may reveal more about other increased risks for age-related cognitive dysfunction or elevated levels of luteinizing hormone caused by gonad removal, and lead to revised guidelines.

A Mapping Study of Veterinary Literature on Perceptions and Attitudes of Female Canine Spaying

This is a mapping study conducted to evaluate the characteristics of where content that engages in perspectives or attitudes on female dog spaying is published. Three databases, CAB Direct, PubMed, and Scopus, were systematically searched. There were 84 out of 642 papers identified and screened for relevance on attitudes or perceptions on female canine spaying. These 84 articles were then examined for recurring authors, institutional representation, and publisher information. Additionally, information regarding the population being addressed, veterinarian or client, was noted with most literature addressing the veterinary perspective. Many important articles were published in a wide array of journals from many countries, which suggests the importance of not only browsing journals but also searching for relevant literature in databases like CAB Abstracts and MEDLINE.

Influence of gender, neuter status, and training method on police dog narcotics olfaction performance, behavior and welfare

OBJECTIVE

This study was carried out to study the influence of gender, neuter status, and training method on police dog narcotics olfaction performance, behavior, and welfare.

MATERIALS AND METHODS

A total of 120 German Shepherds aged 1-3 years were used for this study. The dogs were separated into two experiments. The first experiment (32 dogs and 28 bitches) was used to study the influence of gender on olfaction and smell to narcotics in police dog performance and training methods with behavioral problems and welfare. The second experiment (30 dogs and 30 bitches) was used to study the influence of sexual status (entire or neutered) on the smelling of narcotics in police dog performance by comparing with intact dogs and bitches.

RESULTS

We found that there were significant differences in sex in training to detect narcotics. Male German Shepherds were found to be significantly more trainable than females. Neutering causes a difference in trainability in male and female dogs. Gonadectomy had adverse effects on training. The intact male and female German Shepherds were found to be significantly more trainable than the neutered ones, and the reward-based method was found to be significantly more trainable than punishment. Dog training methods incorporated by punishment result in pain, suffering, emotional instability, symptoms of depression, aggression, unwanted barking, growling at other people, not under control all time, less trainability, increased problematic behavior, and decreased dog welfare.

CONCLUSION

Reward-based method is associated with lower lousy behavior and dogs with good behavior, such as, attachment attention behavior, dogs under the control of handler all times, higher trainability, less problematic behavior, and increased dog welfare.

Assisting Decision-Making on Age of Neutering for Mixed Breed Dogs of Five Weight Categories: Associated Joint Disorders and Cancers

The early neutering of male and female dogs and its relationship to an increased risk of joint disorders and some cancers has recently become a concern, raising questions about the standard practice in the U.S. and much of Europe of neutering by 6 months of age. A noteworthy recent finding from this center is that there are major breed differences with small-dog breeds generally showing little vulnerability to neutering compared with breeds of larger body size. These findings on purebreds raise questions for dog owners and veterinarians about mixed-breed dogs. The purpose of this study was to examine a sample of mixed breed dogs of five weight categories using the same veterinary hospital database and diagnostic criteria for joint disorders and cancers as used in the newly published paper on 35 breeds and previous papers on the Golden Retriever, Labrador Retriever, and German Shepherd Dog. The weight categories were <10 kg (739 cases), 10–19 kg (546 cases), 20–29 kg (992 cases), 30–39 kg (604 cases), and over 40 kg (258 cases). Males and females were analyzed separately, as were various ages at neutering. The joint disorders examined were hip dysplasia, cranial cruciate ligament tear or rupture, and elbow dysplasia. The cancers were lymphoma, mast cell tumor, hemangiosarcoma, and osteosarcoma. There was no significant increased occurrence of one or more cancers, compared with intact dogs, in any weight category. However, in the three categories of dogs weighing 20 kg or more, neutering before 1 year generally was significantly associated with risks of one or more joint disorders above that of dogs left intact, commonly to 3 times the level of intact dogs, with sex differences in the degrees of joint disorders associated with neutering. For the dogs in the two weight categories <20 kg, no increased risks were found for joint disorders. This information can be useful to dog caregivers in deciding on the age at which to neuter specific dogs, and for veterinarians offering guidance to pet owners.

Age influences domestic dog cognitive performance independent of average breed lifespan

Across mammals, increased body size is positively associated with lifespan. However, within species, this relationship is inverted. This is well illustrated in dogs (Canis familiaris), where larger dogs exhibit accelerated life trajectories: growing faster and dying younger than smaller dogs. Similarly, some age-associated traits (e.g., growth rate and physiological pace of aging) exhibit accelerated trajectories in larger breeds. Yet, it is unknown whether cognitive performance also demonstrates an accelerated life course trajectory in larger dogs. Here, we measured cognitive development and aging in a cross-sectional study of over 4000 dogs from 66 breeds using nine memory and decision-making tasks performed by citizen scientists as part of the Dognition project. Specifically, we tested whether cognitive traits follow a compressed (accelerated) trajectory in larger dogs, or the same trajectory for all breeds, which would result in limited cognitive decline in larger breeds. We found that all breeds, regardless of size or lifespan, tended to follow the same quadratic trajectory of cognitive aging-with a period of cognitive development in early life and decline in later life. Taken together, our results suggest that cognitive performance follows similar age-related trajectories across dog breeds, despite remarkable variation in developmental rates and lifespan.

Possible Relationship between Long-Term Adverse Health Effects of Gonad-Removing Surgical Sterilization and Luteinizing Hormone in Dogs

Spaying and neutering dogs is commonly used to prevent the birth of unwanted animals and eliminate the risk of reproductive diseases. However, removal of the gonads prevents the feedback of estrogen and testosterone on the pituitary and hypothalamus. As a result, luteinizing hormone (LH) is continuously elevated at supraphysiologic concentrations. Although the main role of LH is for reproductive function (e.g., ovulation), there are LH receptors present in several normal tissues including the thyroid and adrenal glands, gastrointestinal tract, cranial cruciate ligament and round ligament, and lymphocytes. In addition, there are LH receptors present in several neoplastic tissues (e.g., lymphoma, hemangiosarcoma, mastocytoma, transitional cell carcinoma, and osteosarcoma). The role of LH receptors in non-reproductive normal and neoplastic tissues is not known but may stimulate nitric oxide release and induce cell division. The precise etiology of the increased incidence of several non-reproductive long-term health complications following spaying and neutering is not known but may be related to LH receptor activation in these non-reproductive target tissues. How these effects may be mediated is described in this review.

Desexing Dogs: A Review of the Current Literature

Background: Desexing dogs is promoted for population control, preventative healthcare, and behavior modification. Common methods are orchiectomy and ovariectomy/ovariohysterectomy. GnRH superagonist implants are available in some areas. Alternative methods like vasectomy and salpingectomy/hysterectomy are uncommon. The terminology used to describe desexing is inconsistent and contradictory, showing a need for the adaption of standardized terminology. Population Control: Surprisingly, empirical studies show no effects of desexing on population control in companion and shelter dogs despite desexing being consistently recommended in the literature. There is evidence for a population control effect in free-roaming dogs, where desexing also has benefits on zoonotic disease and bite risk. Population control in free-roaming dogs is mostly correlated with female, not male desexing. Health and Lifespan: Desexing affects numerous disease risks, but studies commonly neglect age at diagnosis and overall lifespan, age being by far the most important risk factor for most diseases. We argue that lifespan is a more important outcome than ultimate cause of death. A beneficial effect of desexing on lifespan is consistently demonstrated in females, while evidence for a beneficial effect in males is inconsistent. Studies are likely biased in desexing being a proxy for better care and desexed dogs having already lived to the age of desexing. Desexing reduces or eliminates common life-limiting diseases of the female reproductive system such as pyometra and mammary tumors, while no analogous effect exists in males. Disease risks increases across sexes and breeds include cruciate ligament rupture, various cancers, and obesity. Urinary incontinence risk is increased in females only. Various other disease risk changes show considerable variability between breeds and sexes. Behavioral Effects: Desexed males show reduced libido, roaming, conspecific mounting, and urinary marking frequency, as well as reduced male dog-directed aggression in a majority of males desexed for behavioral reasons. There is a detrimental effect on the risk and progression of age-related cognitive dysfunction. Desexed dogs may be less likely to cause bite injuries across sexes. The evidence for other effects such as human-directed aggression, human or object mounting, resource guarding, or shyness and anxiety is inconsistent and contradictory. There are few studies specific to females or individual breeds. Conclusions: The evidence for a beneficial effect of desexing is stronger in female than in male dogs; however, there is significant variation between breeds and sexes, and more research is needed to further elucidate these differences and to arrive at individualized evidence-based recommendations for clinical practice.

A cross-species approach to disorders affecting brain and behaviour

Structural and functional elements of biological systems are highly conserved across vertebrates. Many neurological and psychiatric conditions affect both humans and animals. A cross-species approach to the study of brain and behaviour can advance our understanding of human disorders via the identification of unrecognized natural models of spontaneous disorders, thus revealing novel factors that increase vulnerability or resilience, and via the assessment of potential therapies. Moreover, diagnostic and therapeutic advances in human neurology and psychiatry can often be adapted for veterinary patients. However, clinical and research collaborations between physicians and veterinarians remain limited, leaving this wealth of comparative information largely untapped. Here, we review pain, cognitive decline syndromes, epilepsy, anxiety and compulsions, autoimmune and infectious encephalitides and mismatch disorders across a range of animal species, looking for novel insights with translational potential. This comparative perspective can help generate novel hypotheses, expand and improve clinical trials and identify natural animal models of disease resistance and vulnerability.

The Views of the UK Public Towards Routine Neutering of Dogs and Cats

Despite being routinely recommended by veterinarians, neutering of dogs and cats has both positive and negative impacts on animal welfare and is ethically problematic. We examined attitudes of a sample of the UK public towards routine neutering of dogs and cats using a questionnaire. Respondents indicated their level of agreement with statements describing welfare and ethical reasons 'for' and 'against' the neutering of male and female dogs and cats. We conducted a general linear model (GLM) analysis to investigate the effects of demographic factors on agreement scores. Respondents (n = 451) expressed views both supporting and opposing neutering. The predominant view (>80%) supported neutering, justified primarily by prevention of unwanted offspring and reproductive diseases. Around 10% of the respondents disagreed and felt that neutering should only be done for medical reasons. Men were less likely than women to support neutering (p < 0.001). Those with meat reduction diets were more likely to be against neutering (p < 0.05) and cat owners supported neutering more than non-cat owners (p < 0.05). Although the data reflected a wide range of ethical views, our findings show that the UK public generally supports the routine neutering of dogs and cats. This insight has implications for future policy-making and compliance with veterinary advice.

Owner reported sensory impairments affect behavioural signs associated with cognitive decline in dogs

To describe the extent of age-related cognitive decline in dogs, information regarding the baseline occurrence of associated behaviours in the general population is necessary. With a seven-item, data driven Age-Related Changes scale, we evaluated the relationship between sensory functions, training, sex, and the occurrence of behavioural signs associated with cognitive decline across the whole adult lifespan. The twofold difference in lifespan between small and large dogs presents challenges for ageing studies, with no widely accepted method to control for body size as it relates to chronological age and longevity, when comparing behavioural signs of cognitive decline. To address this issue, we utilized relative age, calculated using the estimated expected lifespan of the individuals in our questionnaire study. Signs of cognitive decline were already detectable in' Mature' dogs (at 50-75% of the expected lifespan). Visual, auditory and olfactory impairments all resulted in significantly higher scores on the Age-Related Changes scale. Participating in dog training activities was revealed to be protective against behavioural signs of cognitive decline in aged dogs as perceived by the owners. These results revealed possible beneficial effects of training on cognitive ageing and emphasize the importance of routinely screening the sensory capacities of ageing dogs.

Exploring the potential of natural and synthetic neuroprotective steroids against neurodegenerative disorders: A literature review

Neurodegeneration is a complex process, which leads to progressive brain damage due to loss of neurons. Despite exhaustive research, the cause of neuronal loss in various degenerative disorders is not entirely understood. Neuroprotective steroids constitute an important line of attack, which could play a major role against the common mechanisms associated with various neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Natural endogenous steroids induce the neuroprotection by protecting the nerve cells from neuronal injury through multiple mechanisms, therefore the structural modifications of the endogenous steroids could be helpful in the generation of new therapeutically useful neuroprotective agents. The review article will keep the readers apprised of the detailed description of natural as well as synthetic neuroprotective steroids from the medicinal chemistry point of view, which would be helpful in drug discovery efforts aimed toward neurodegenerative diseases.

Correlation of neuter status and expression of heritable disorders

BACKGROUND

Gonadectomy, or neutering, is a very common surgery for dogs having many positive effects on behavior, health, and longevity. There are also certain risks associated with neutering including the development of orthopedic conditions, cognitive decline, and a predisposition to some neoplasias. This study was designed specifically to identify if a correlation exists between neuter status and inherited conditions in a large aggregate cohort of dogs representing many different breeds.

RESULTS

Neutered dogs were at less risk for early and congenital conditions (aortic stenosis, early onset cataracts, mitral valve disease, patent ductus arteriosus, portosystemic shunt, and ventricular septal defect) than intact dogs. Neutering was also associated with reduced risk of dilated cardiomyopathy and gastric dilatation volvulus in males. Neutering was significantly associated with an increased risk for males and females for cancers (hemangiosarcoma, hyperadrenocorticism, lymphoma, mast cell tumor, and osteosarcoma), ruptured anterior cruciate ligament and epilepsy. Intervertebral disk disease was associated with increased risk in females only. For elbow dysplasia, hip dysplasia, lens luxation, and patellar luxation neutering had no significant effect on the risk for those conditions. Neutering was associated with a reduced risk of vehicular injury, a condition chosen as a control.

CONCLUSIONS

In this retrospective study, several conditions showed an increased risk associated with neutering whereas other conditions were less likely to be expressed in neutered dogs. The complexity of the interactions between neutering and inherited conditions underscores the need for reflective consultation between the client and the clinician when considering neutering. The convenience and advantages of neutering dogs that will not be included in a breeding program must be weighed against possible risk associated with neutering.

Risk factors for canine cognitive dysfunction syndrome in Slovakia

Background

Increasing prevalence of cognitive impairment in an aging canine population poses a serious health problem. Identifying risk factors, which may influence the onset of cognitive decline, is becoming increasingly important. Here we investigated whether age, sex, weight, nutrition, dogs’ housing and reproductive state were associated with increased risk of canine cognitive dysfunction syndrome (CCDS) in Slovakia.

Results

Age was associated with cognitive decline and nutrition emerged as a significant predictor variable. Dogs fed controlled diets had 2.8 times lower odds of developing CCDS when compared with dogs fed uncontrolled diets. Sex, weight, reproductive state and dogs’ housing were not significantly associated with cognitive decline. Further, the prevalence of CCDS was similar in both small and medium/large sized dogs aged 8–11 years, but differed in dogs at an age of 11–13 years.

Conclusion

Age was found to be the most prominent risk factors of CCDS. Nutrition may influence the cognitive state of dogs. This finding suggests that nutritional interventions may modify canine cognitive functions.

Long-term effects of castration on the skeleton of male rhesus monkeys (Macaca mulatta)

While osteopenia (OPE) and osteoporosis (OPO) have been studied in various species of aging nonhuman primates and extensively in ovariectomized rhesus and cynomolgus macaques, there is virtually no information on the effects of castration on the skeleton of male nonhuman primates. Most information on castrated male primates comes from a few studies on the skeletons of eunuchs. This report used a subset of the Caribbean Primate Research Center's (CPRC) Cayo Santiago (CS) rhesus macaque skeletal collection to qualitatively and quantitatively compare the bone mineral density (BMD) of castrated and age-matched intact males and, thereby, determine the long-term effects of castration (orchidectomy) on bone. Lumbar vertebrae, femora, and crania were evaluated using dual-energy X-ray absorptiometry (DEXA or DXA) and digital radiography augmented, when fresh tissues were available, with autoradiography and histology. Results confirmed physical examinations of long bones that castration causes changes in the skeleton of male rhesus macaques similar to those found in eunuchs, including OPE and OPO of the vertebrae and femora, thinning of the skull, and vertebral fractures and kyphosis of the spine more severe than that caused by normal aging alone. Also like eunuchs, some castrated CS male rhesus monkeys had a longer life span than intact males or females. Based on these results and the effects of castration on other tissues and organs of eunuchs, on behavior, hormone profiles and possibly on cognition and visual perception of human and nonhuman primates, and other mammals, castrated male rhesus macaques should be used with caution for laboratory studies and should be considered a separate category from intact males. Despite these caveats, the castrated male rhesus macaque should make an excellent animal model in which to test hormone replacement therapies for boys and men orchidectomized for testicular and prostate cancer.

Long-term health effects of neutering dogs: comparison of Labrador Retrievers with Golden Retrievers

Our recent study on the effects of neutering (including spaying) in Golden Retrievers in markedly increasing the incidence of two joint disorders and three cancers prompted this study and a comparison of Golden and Labrador Retrievers. Veterinary hospital records were examined over a 13-year period for the effects of neutering during specified age ranges: before 6 mo., and during 6–11 mo., year 1 or years 2 through 8. The joint disorders examined were hip dysplasia, cranial cruciate ligament tear and elbow dysplasia. The cancers examined were lymphosarcoma, hemangiosarcoma, mast cell tumor, and mammary cancer. The results for the Golden Retriever were similar to the previous study, but there were notable differences between breeds. In Labrador Retrievers, where about 5 percent of gonadally intact males and females had one or more joint disorders, neutering at <6 mo. doubled the incidence of one or more joint disorders in both sexes. In male and female Golden Retrievers, with the same 5 percent rate of joint disorders in intact dogs, neutering at <6 mo. increased the incidence of a joint disorder to 4–5 times that of intact dogs. The incidence of one or more cancers in female Labrador Retrievers increased slightly above the 3 percent level of intact females with neutering. In contrast, in female Golden Retrievers, with the same 3 percent rate of one or more cancers in intact females, neutering at all periods through 8 years of age increased the rate of at least one of the cancers by 3–4 times. In male Golden and Labrador Retrievers neutering had relatively minor effects in increasing the occurrence of cancers. Comparisons of cancers in the two breeds suggest that the occurrence of cancers in female Golden Retrievers is a reflection of particular vulnerability to gonadal hormone removal.

Neutering dogs: effects on joint disorders and cancers in golden retrievers

In contrast to European countries, the overwhelming majority of dogs in the U.S. are neutered (including spaying), usually done before one year of age. Given the importance of gonadal hormones in growth and development, this cultural contrast invites an analysis of the multiple organ systems that may be adversely affected by neutering. Using a single breed-specific dataset, the objective was to examine the variables of gender and age at the time of neutering versus leaving dogs gonadally intact, on all diseases occurring with sufficient frequency for statistical analyses. Given its popularity and vulnerability to various cancers and joint disorders, the Golden Retriever was chosen for this study. Veterinary hospital records of 759 client-owned, intact and neutered female and male dogs, 1–8 years old, were examined for diagnoses of hip dysplasia (HD), cranial cruciate ligament tear (CCL), lymphosarcoma (LSA), hemangiosarcoma (HSA), and mast cell tumor (MCT). Patients were classified as intact, or neutered early (<12 mo) or late (≥12 mo). Statistical analyses involved survival analyses and incidence rate comparisons. Outcomes at the 5 percent level of significance are reported. Of early-neutered males, 10 percent were diagnosed with HD, double the occurrence in intact males. There were no cases of CCL diagnosed in intact males or females, but in early-neutered males and females the occurrences were 5 percent and 8 percent, respectively. Almost 10 percent of early-neutered males were diagnosed with LSA, 3 times more than intact males. The percentage of HSA cases in late-neutered females (about 8 percent) was 4 times more than intact and early-neutered females. There were no cases of MCT in intact females, but the occurrence was nearly 6 percent in late-neutered females. The results have health implications for Golden Retriever companion and service dogs, and for oncologists using dogs as models of cancers that occur in humans.

Estrogen-regulated synaptogenesis in the hippocampus: sexual dimorphism in vivo but not in vitro

Hippocampal neurons are capable of synthesizing estradiol de novo. Estradiol synthesis can be suppressed by aromatase inhibitors and by knock-down of steroid acute regulatory protein (StAR), whereas elevated levels of substrates of steroidogenesis enhance estradiol synthesis. In rat hippocampal cultures, the expression of estrogen receptors (ERs) and synaptic proteins, as well as synapse density, correlated positively with aromatase activity, regardless of whether the cultures originated from males or females. All effects induced by the inhibition of aromatase activity were rescued by application of estradiol to the cultures. In vivo, however, systemic application of letrozole, an aromatase inhibitor, induced synapse loss in female rats, but not in males. Furthermore, in the female hippocampus, density of spines and spine synapses varied with the estrus cycle. In addressing this in vivo-in vitro discrepancy, we found that gonadotropin-releasing hormone (GnRH) regulated estradiol synthesis via an aromatase-mediated mechanism and consistently regulated spine synapse density and the expression of synaptic proteins. Along these lines, GnRH receptor density was higher in the hippocampus than in the cortex and hypothalamus, and estrus cyclicity of spinogenesis was found in the hippocampus, but not in the cortex. Since GnRH receptor expression also varies with the estrus cycle, the sexual dimorphism in estrogen-regulated spine synapse density in the hippocampus very likely results from differences in the GnRH responsiveness of the male and the female hippocampus. This article is part of a Special Issue entitled 'Neurosteroids'.

Clinical signs and management of anxiety, sleeplessness, and cognitive dysfunction in the senior pet

Physical signs of old age may be obvious, but mental and cognitive changes require more careful observation. Changes in behavior may represent the earliest indications of medical problems, or disorders of the central nervous system, and these may be bidirectional. Cognitive dysfunction syndrome is underdiagnosed and affects a substantial portion of aged companion animals. This article describes potential treatment regimens to address age-related behavioral problems, as well as a framework for investigating differential diagnoses. Early identification of changes in behavior is essential for the adequate treatment and management of medical and behavioral problems, and for monitoring outcomes.

AAHA canine life stage guidelines

Guidelines are offered to guide the veterinary practitioner in designing a comprehensive, individualized wellness plan for each stage of a dog's life. Life stages are defined by both age and breed characteristics for practical purposes. Each patient visit should use an individualized approach to patient handling, preventive care, and early disease detection. Environment, behavior, nutrition, parasite control, vaccinations, dental care, zoonotic disease control, safety, and reproductive health should be addressed.

Survey of veterinary practice policies and opinions on neutering dogs

A cross-sectional survey was conducted in 2008 to obtain information on the advice veterinary practices currently give to their clients and the opinions of veterinary surgeons regarding neutering of dogs. An additional survey of dog owners was conducted to obtain information on the neuter status of the general dog population in Great Britain. A significantly higher proportion of practices had a policy for the age of neutering bitches than for dogs. The average recommended age for neutering bitches was 6.5 months (95 per cent confidence interval [CI] 3.1 to 9.7 months) and for dogs it was 7.5 months (95 per cent CI 1.4 to 13.6 months). There was very little agreement between veterinary practices as to whether bitches should be allowed to have their first season before neutering, with 164 of 973 respondents (16.9 per cent) always recommending this, 198 (20.3 per cent) recommending it most of the time, 203 (20.9 per cent) sometimes, 203 (20.9 per cent) rarely and 201 (20.6 per cent) never recommending it. The owner study showed that 54 per cent of dogs (233 of 431) were neutered, with the North region having the lowest proportion of neutered dogs (11 of 25; 44.0 per cent).

The opposing roles of estradiol on synaptic protein expression in hippocampal cultures

Estrogen-induced synaptic plasticity was frequently shown by an increase of spines at apical dendrites of CA1 pyramidal neurons after systemic application of estradiol to ovariectomized rats. Surprisingly, exogenous application of estradiol to hippocampal cultures had no effect on spines and on spine synapses, although quantitative immunohistochemistry revealed an upregulation of spinophilin and of synaptophysin, in these cultures. The role of synaptophysin as a presynaptic marker and of spinophilin as a postsynaptic marker, appears questionable from these discrepancies. In contrast, synaptopodin, a marker protein of "mature" mushroom-shaped spines, was downregulated after treatment of hippocampal cultures with estradiol. Synaptopodin is strongly associated to the spine apparatus, a spine-specific cell organelle, which is present in 80% of all mushroom-shaped spines. Consistently, we found a reduction in the number of spines, containing a spine apparatus in response to estradiol, suggesting that the presence of a spine apparatus in many but not all spines is very likely a result of their dynamic character. In summary, synaptic proteins appear to be regulated by estradiol, independent of its function on spine and spine synapse formation.

Senescence of the human immune system

The umbrella term 'immunosenescence' is applied to describe age-associated failing systemic immunity and is believed to contribute to the increased incidence and severity of infectious disease in old animals and people. Very limited studies in man have begun to reveal biomarkers of immune ageing ('immune signatures') increasingly recognized as an 'immune risk profile' (IRP) predicting mortality in the elderly. Even more limited studies in companion animals seem consistent with the idea that most or all other mammals may also show an IRP. It is of practical and scientific interest to more accurately determine the IRP and to devise interventions to modulate immune ageing. In man, cytomegalovirus (CMV) infection has an enormous impact on biomarkers associated with immunosenescence; it is not clear whether the same is true for a persistent viral infection in other animals. A significant fraction of the human immune system is committed to controlling CMV; this commitment increases with age and may itself cause pathology as a result of maintaining higher systemic levels of inflammatory mediators. It will be interesting to test whether similar phenomena occur in relatively long-lived animals, often sharing a human environment, like cats and dogs, and whether interventions to restore appropriate immunity in companion animals might also be applicable to people.

Prevalence and risk factors of behavioural changes associated with age-related cognitive impairment in geriatric dogs

OBJECTIVES

The aim of this study was to describe the prevalence and severity of behavioural changes associated with age and their relationship to risk factors such as sex, reproductive status, bodyweight and age.

METHODS

A cross-sectional study design was chosen. A total of 325 geriatric dogs were included. Owners of dogs older than nine years were interviewed by a veterinary behaviourist. Structured phone interviews were used to gather information about four behavioural categories related to cognitive impairment: sleep/wake cycles, social interaction, learning and house training and signs of disorientation.

RESULTS

Signs of cognitive impairment showed a prevalence of 22.5 per cent in geriatric dogs. Sex and age emerged as significant predictor variables. Females and neutered dogs were significantly more affected than males and entire dogs, respectively. Prevalence and severity increased with age. Although weight was not a statistically significant predictor variable, smaller animals had greater odds of showing age-related cognitive impairment. The most impaired behavioural categories were social interaction and house training.

CLINICAL SIGNIFICANCE

Age-related behavioural changes should be considered by practicing veterinarians because of their relative high prevalence among geriatric dogs, especially in females.

Oxidative stress, aging, and central nervous system disease in the canine model of human brain aging

Decline in cognitive functions that accompany aging in dogs may have a biologic basis, and many of the disorders associated with aging in dogs may be mitigated through dietary modifications that incorporate specific nutraceuticals. Based on previous research and the results of laboratory and clinical studies, antioxidants may be one class of nutraceutical that provides benefits to aged dogs. Brains of aged dogs accumulate oxidative damage to proteins and lipids, which may lead to dysfunction of neuronal cells. The production of free radicals and lack of increase in compensatory antioxidant enzymes may lead to detrimental modifications to important macromolecules within neurons. Reducing oxidative damage through food ingredients rich in a broad spectrum of antioxidants significantly improves, or slows the decline of, learning and memory in aged dogs.

Therapeutic Options for Cognitive Decline in Senior Pets

Many treatment options are now available for pets with age-related cognitive dysfunction, including drugs, nutritional supplements, and diets. This article describes the theory, evidence of efficacy, and potential neuroprotective effects of products used to treat cognitive dysfunction. Cognitive dysfunction is a diagnosis of exclusion, because many painful conditions and health problems may present with similar signs. Practitioners must, therefore, actively question owners of senior pets in order to diagnose cognitive dysfunction and to assess the pet’s general health and well-being.

Reproductive behavior of small animals

Normal and abnormal reproductive behavior of dogs and cats, and known and proposed hormonal bases for these behaviors are addressed. Emerging information includes use of oxytocin to promote pair-bonding between dam and offspring and the possible effect of prolactin in inhibiting sexual behaviors.

Behavior Problems in Geriatric Pets

Aging pets often suffer a decline in cognitive function (eg, memory,learning, perception, awareness) likely associated with age-dependent brain alterations. Clinically, cognitive dysfunction may result in various behavioral signs, including disorientation; forgetting of previously learned behaviors, such as house training; alterations in the manner in which the pet interacts with people or other pets;onset of new fears and anxiety; decreased recognition of people, places, or pets; and other signs of deteriorating memory and learning ability. Many medical problems, including other forms of brain pathologic conditions, can contribute to these signs. The practitioner must first determine the cause of the behavioral signs and then determine an appropriate course of treatment, bearing in mind the constraints of the aging process. A diagnosis of cognitive dysfunction syndrome is made once other medical and behavioral causes are ruled out.

Therapeutic agents for the treatment of cognitive dysfunction syndrome in senior dogs

With increasing age, dogs develop a form of neurodegenerative disease which has many similarities to age related cognitive impairment and Alzheimer's disease in humans. A decline in learning and memory can be demonstrated in dogs beginning as young as 7 years of age using a variety of neuropsychological tests. However, clinical cases of cognitive dysfunction syndrome are seldom identified until the age of 11 years or older. This is likely due to the fact that the owners are relying on clinical observations such as house-soiling, sleep-wake cycles and disorientation, rather than tests of learning and memory. On the other hand, dogs that are trained to more exacting tasks such as guide dogs for the visually impaired, or bomb detection and agility trained dogs might be noticed to have a decline in performance at a much earlier age. Through the use of standardized neuropsychological testing protocols, a number of drugs, natural products and supplement formulations have been developed for use in dogs with cognitive dysfunction and, in some cases clinical trials have validated their efficacy. Furthermore, the testing of products currently licensed and in the pipeline for the treatment of cognitive decline and Alzheimer's in humans, may provide additional therapeutic agents for the treatment of senior dogs, as well as provide insight as to the potential for the efficacy of these compounds in humans. This review will examine those products that are now marketed along with some that might be considered for use in senior dogs with cognitive dysfunction as well as the research that has been used to validate the efficacy (or lack thereof) of these compounds.

Nutraceuticals, aging, and cognitive dysfunction

Decline in cognitive function that accompanies aging in dogs might have a biological basis, and many of the disorders associated with aging in canines might be preventable through dietary modifications that incorporate specific nutraceuticals. Based on previous research and the results of laboratory and clinical studies, antioxidants might be one class of nutraceutical that benefits aged dogs. Brains of aged dogs accumulate oxidative damage to proteins and lipids, which can lead to dysfunction of neuronal cells. The production of free radicals and lack of increase in compensatory antioxidant enzymes might lead to detrimental modifications to important macromolecules within neurons. Reducing oxidative damage through food ingredients rich in a broad spectrum of antioxidants significantly improves, or slows the decline of, learning and memory in aged dogs; however, determining which compounds, combinations, dosage ranges, when to initiate intervention, and long-term effects constitute critical gaps in knowledge about this subject.

Testosterone's Analgesic, Anxiolytic, and Cognitive-Enhancing Effects May Be Due in Part to Actions of Its 5α-Reduced Metabolites in the Hippocampus

Although testosterone (T) may decrease anxiety and enhance cognitive performance, its mechanisms are not well understood. The authors hypothesized that if T's effects are mediated in part through actions of its 5alpha-reduced, nonaromatizable metabolite dihydrotestosterone (DHT) and/or its 3alpha-hydroxysteroid dehydrogenase reduced metabolite 3alpha-androstanediol (3alpha-diol) in the hippocampus, then T, DHT, and 3alpha-diol administration should produce similar behavioral effects concomitant with elevating T metabolites in the hippocampus. Gonadectomized male rats administered T, DHT, or 3alpha-diol via Silastic capsules or intrahippocampal infusions had greater analgesia (tail flick, paw lick), less anxiety behavior (plus-maze, open field, defensive freezing), and better learning (inhibitory avoidance) compared with vehicle control rats. Only 3alpha-diol levels in the hippocampus were consistently elevated in conjunction with these behavioral effects.

Role of androgens in mild cognitive impairment and possible interventions during andropause

Mild cognitive impairment (MCI) is becoming fashionable as a diagnosis, representing a state of cognitive decline associated with negligible functional loss. MCI is important as it often precedes Alzheimer's disease (AD). Recognizing MCI may lead to preventive strategies that can delay the onset of AD. Many patients who transition into andropause report problems with their memory. There is strong evidence from basic sciences and epidemiological studies that both estrogens and androgens play a protective role in neurodegeneration. The evidence from small prospective clinical trials lends support to the role of hormones in improving cognitive function. The improvement in cognitive function with hormones is subtle and often not measurable on standard neuropsychological batteries. Patients have reported memory improvements in both declarative and procedural domains after being on hormonal replacement. Functional changes and vascular changes can be detected after hormonal replacement with more sophisticated imaging of the brain like PET scans. We hypothesize androgens and perhaps selective androgen receptor modulators as future treatment options for MCI in aging males.

Gonadal hormones affect spine synaptic density in the CA1 hippocampal subfield of male rats

The effects of androgen on the density of spine synapses on pyramidal neurons in the CA1 area of the hippocampus were studied in male rats. Gonadectomy (GDNX) had no significant effect on the number of CA1 pyramidal cells but reduced CA1 spine synapse density by almost 50% (to 0.468 +/- 0.018 spine synapses/microm(3)) compared with sham-operated controls (0.917 +/- 0.06 spine synapses/microm(3)). Treatment of GDNX rats with testosterone propionate (500 microg/d, s.c., 2 d) increased spine synapse density to levels (1.01 +/- 0.026 spine synapses/microm(3)) comparable with intact males. A similar increase in synapse density (1.013 +/- 0.05 spine synapses/microm(3)) was observed in GDNX animals after treatment with dihydrotestosterone (DHT) (500 microg/d, s.c., 2 d) but not after estradiol (10 microg/d, s.c., 2 d; 0.455 +/- 0.02 spine synapse/microm(3)). These data indicate that testosterone is important for maintenance of normal spine synapse density in the CA1 region of the male rat hippocampus. The comparable responses to testosterone and the non-aromatizable androgen DHT, coupled with the lack of response to estradiol, suggest that testosterone acts directly on hippocampal androgen receptors rather than indirectly via local estrogen biosynthesis.

Role of androgens in mild cognitive impairment and possible interventions during andropause

Mild cognitive impairment (MCI) is becoming fashionable as a diagnosis, representing a state of cognitive decline associated with negligible functional loss. MCI is important as it often precedes Alzheimer's disease (AD). Recognizing MCI may lead to preventive strategies that can delay the onset of AD. Many patients who transition into andropause report problems with their memory. There is strong evidence from basic sciences and epidemiological studies that both estrogens and androgens play a protective role in neurodegeneration. The evidence from small prospective clinical trials lends support to the role of hormones in improving cognitive function. The improvement in cognitive function with hormones is subtle and often not measurable on standard neuropsychological batteries. Patients have reported memory improvements in both declarative and procedural domains after being on hormonal replacement. Functional changes and vascular changes can be detected after hormonal replacement with more sophisticated imaging of the brain like positron emission tomography (PET) scans. We hypothesize androgens and perhaps selective androgen receptor modulators as future treatment options for MCI in aging males.