National Anti-vivisection Society

 

National Antivisection Society

Case study: research using rabbits funded by Diabetes UK

Posted: 13 December 2011. Updated: 17 April 2012

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Sergeant, G. P. et al (2009) “Spontaneous Ca2+ Waves in Rabbit Corpus Cavernosum: Modulation by Nitric Oxide and cGMP”, Journal of Sexual Medicine, vol. 6, pp: 958 – 966

Diabetes UK

This study used male New Zealand White rabbits to study the corpus cavernosum taken from the penis and whether smooth muscle calcium (Ca2+) waves were regulated by nitric oxide (NO). An unspecified number of rabbits were killed with an overdose of anaesthetic and their penises removed. The penises were dissected, the relevant parts taken and cells used in calcium imaging on a plate, or in whole slice tissue experiments.

Repetition

Some of the authors have previously carried out the same procedures in rabbits, with a very similar study, also funded by Diabetes UK (1) The paper described rabbits being killed in order to remove their penises and use the tissue in experiments to investigate cellular mechanisms of penile erection. In fact, the current paper cites the 2004 paper in explaining the methods used, demonstrating the repeated use of male rabbits for very similar experiments over a number of years.

Both studies concluded that NO has an influence on penile erection – something which was already elucidated in the earlier paper.

Species differences and awareness of them

The researchers do not address any differences between human and rabbit physiology. A 2006 paper described differences between rabbit and human penises, including differences between the corpus cavernosum of the two species; “we observed a larger amount of elastic fibres in the rabbit penis than in human penis components” (2)

Current available treatments

Erectile dysfunction (ED) may be caused by an underlying physiological condition, such as diabetes, or psychological conditions. Treating the cause may resolve the problem of ED. Hormonal treatment may be given if a hormonal condition is the underlying cause, and lifestyle changes can also have an impact. These include losing weight, giving up smoking, taking exercise and reducing stress. There are also some medications which temporarily increase the blood flow to the penis. It is also possible for men to use “vacuum pumps” which cause the penis to fill with blood and a ring is used keep the blood in place. Surgery is only recommended if all other treatments have failed, or in younger men (3)

Animal suffering

The animals were killed before their penises were removed. However, there is no mention of the housing and environmental conditions in which the animals were kept prior to the investigation and how the animals were handled and if they were restrained. This information is important especially considering that it is known that routine laboratory procedures predictably cause “significant fear, stress, and possibly distress” (4). In addition, these were young animals; 16 – 20 weeks old.

Alternative advance techniques

The researchers cite research in which human erectile tissue was used. This study, published more than two decades ago, utilised human isolated erectile tissue from patients undergoing surgery to implant penile prostheses. Specific contractions in the tissue were “reliably assayed up to 24h after surgical removal” and the study demonstrated mechanisms involved in the spontaneous contractions of the human tissues. Importantly, it was stated that “Pharmacological studies on human isolated vascular smooth muscle tissues represent an initial step toward understanding mechanisms of contraction and relaxation in vivo and, ultimately, toward characterization of alterations in vascular smooth muscle function related to age and pathology.” (5)

This demonstrates that comparable human tissue studies are possible and have been for some time.

Poor experimental planning

The paper fails to describe basic information such as the animals housing and environment, and even the number of animals used. Clearly the number of animals used is important to assess if the results are of statistical significance. This is also vital to show if an excessive number of animals were used. The housing of laboratory rabbits is also important, because certain aspects such as social contact and a “bolt-hole” are important to them (6) and because enrichment can “have a major impact on the laboratory animal throughout its life and will thereby influence the outcome of animal experiments” (7)

Disease context

Erectile dysfunction is a highly prevalent condition which is associated with age as well as important co-morbidities such as diabetes (8). One study showed that prevalence over the world ranges from 2% in men under 40 years old, up to 86% in men who are 80 years and older (9)

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References:

1.Craven, M et al (2004) “Modulation of spontaneous Ca2+ -activated Cl- currents in the rabbit corpus cavernosum by the nitric oxide-cGMP pathway” Journal of Physiology, vol. 556.2, pp: 495 - 506.
2.Miai, R.S et al (2006) “Concentration of elastic system fibres in the corpus cavernosum, corpus spongiosum, and tunica albuginea in the rabbit penis, International Journal of Impotence Research, vol. 18, pp: 121-125.
3.http://www.nhs.uk/Conditions/Erectile-dysfunction/Pages/Treatment.aspx - accessed 04/10/11
4.Balcombe, J. P et al (2004) “Laboratory Routines Cause Animal Stress” Contemporary Topics, vol. 43, no. 6, pp:42 - 51.
5.Christ, G. J et al (1990) “Pharmacological studies of human erectile tissue: characteristics of spontaneous contradictions and alterations in α-adrenoreceptor responsiveness with age and disease in isolated tissues” British Journal of Pharmacology, vol. 101, pp:375-381
6.Seaman, S. C (2002) “Laboratory rabbit housing: An investigation of the social and physical environment”, University of Edinburgh,
7.Baumans, V (2005) “Environmental Enrichment for Laboratory Rodents and Rabbits: Requirements of Rodents, Rabbits, and Research, ILAR Journal, vol. 46, no. 2, p:162 - 170.
8.Mulcahy. J. J, (2006) Chapter 2 Epidemiology of Erectile Dysfunction, in Male sexual function: a guide to clinical management, Humana Press, USA
9.Prins, J et al (2002) “Prevalence of erectile dysfunction: a systematic review of population-based studies” International Journal of Impotence Research, vol. 14, pp: 422 - 432.

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