The impact of body site, topical melatonin and brushing on hair regrowth after clipping normal siberian husky dogs

Veterinary Dermatology 2006, 17, 45– 50
Blackwell Publishing Ltd The impact of body site, topical melatonin and brushing on hair
regrowth after clipping normal Siberian Husky dogs
SANDRA F. DIAZ, SHEILA M. F. TORRES, SANDRA A. F. NOGUEIRA, SOPHIE GILBERT and CARL R. JESSEN Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Paul, (Received 9 January 2005; accepted 18 November 2005) The aims of this study were to determine the impact of body site, vigorous brushing and topical mela- tonin treatment on hair regrowth after clipping normal dogs. Siberian Husky dogs were randomly assigned tothree groups of eight dogs each. All dogs had the lumbosacral region and both lateral thighs clipped. The leftthigh and lumbosacral area received no treatment and were compared in all 24 dogs. Eight dogs had the rightthigh treated with 0.1% melatonin twice daily for 2 months, and hair regrowth was compared with the left thigh.
Eight dogs had the right thigh brushed twice daily for 2 months, and hair regrowth was compared with the leftthigh. Eight dogs had neither thigh treated. Hairs were plucked before and 2 months postclipping, and the pro-portion of hair growth from the original length was calculated and compared as described above. Biopsy sampleswere collected before and after treatment to determine if brushing induced dermal inflammation and melatoninincreased the proportion of anagen follicles. Proportionally, left thigh hairs were significantly longer comparedto lumbosacral hairs 2 months postclipping. No significant differences in hair regrowth were noted between thenontreated thigh and the thigh treated with melatonin or brushed. No significant difference in dermal inflam-mation was noted before and after brushing. No significant differences were observed in the proportion of anagenfollicles before and after topical melatonin treatment. Our results showed that the hairs in the lumbosacral regionwere proportionally shorter than lateral thigh hairs 2 months postclipping. Moreover, topical melatonin andbrushing had no impact on hair regrowth after clipping normal dogs.
I N T RO D U C T I O N
Skin histopathology of dogs that experience delay in hair regrowth postclipping shows hair follicle arrest.10 The delay in hair regrowth after clipping is a well- An interesting and frequently observed finding in these recognized but a poorly understood condition that worries cases is the regrowth of tufts of hairs at the biopsy site many pet owners who take pride in their pet's coat. Con- a few weeks after the procedure.10 This has also been cerned owners frequently ask veterinarians how they can reported in follicular arrest associated with endocrine help accelerate hair regrowth. Few studies have evaluated alopecia, suggesting that local inflammation stimulates factors that influence canine hair growth and those that hair regrowth.11,12 However, to our knowledge, no exist are uncontrolled and include few dogs.1–4 controlled studies have been conducted to determine Hair growth is controlled by complex interactions whether induced skin inflammation stimulates hair between endogenous and exogenous influences.5–7 It has often been observed that hairs on the lumbosacral Melatonin is thought to play either a direct or an indi- region grow more slowly than hairs on the lateral thigh rect role in the neuroendocrine control of moulting and when both areas are clipped for hip surgery. Troncy hair growth in mammals.13–15 In dogs, oral melatonin et al. noticed while investigating two epidural anaes- has been used to treat various forms of alopecia, such as thesia protocols that 11% of the dogs included in the recurrent flank alopecia, pattern baldness and alopecia- study experienced a delay in hair regrowth on the lum- X of the Nordic breeds, with variable success.16–19 bosacral region after clipping.8 Preliminary data from Researchers have investigated the therapeutic use of a study conducted in Greece indicated that neither melatonin in humans as well. In a recent study per- epidural anaesthesia nor scrubbing or clipping seems formed in women with either androgenic or diffuse to affect hair regrowth in this area.9 These results seem alopecia, topically applied 0.1% melatonin led to a to confirm the frequent anecdotal finding that body significant increase in anagen hair rate when compared region has an impact on hair regrowth postclipping.
with placebo.20 It is tempting to investigate the impactof topical melatonin on hair regrowth in dogs withpostclipping follicular arrest. Topical application of Correspondence: Dr Sheila M. F. Torres, Department of Small melatonin has been shown to limit the drug effect to Animal Clinical Sciences, College of Veterinary Medicine, University treated areas, thus allowing higher concentrations at or Minnesota, C339 Veterinary Hospitals, 1352 Boyd Avenue, SaintPaul, MN 55108, USA. E-mail: [email protected] the treated sites, which may increase the chances of 2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology SF Diaz et al. success.20 Therefore, the aim of this study was to deter- of the neutroceutical 0.1% melatonin in alcohol (99.1% mine the impact of body site, vigorous brushing and bulk melatonin powder Village Drug, Northfield, MN, topical melatonin treatment on hair regrowth after USA),20 and the left lateral thigh served as control.
clipping the hair coat of healthy Siberian Husky dogs.
Based on a pilot study, the amount of solution necessaryto cover the clipped area was determined to be approxi-mately 0.5 mL. A spray bottle capable of delivering 0.1 mL per pump was used to apply the melatoninsolution; therefore, five pumps of melatonin solution Study population were applied to the clipped area on the right thigh twice Privately owned intact male Siberian Husky sled dogs daily for 2 months. As with group 2, hair regrowth were considered for inclusion in the study. This group of between the right and left thighs and between the dogs was deliberately chosen because the dogs were of the lumbosacral area and the left thigh was compared.
same breed and gender, kept in the same environmentalconditions and fed the same diet for the duration of the Follow-up of hair regrowth study, which was conducted during a single season (July Before clipping, hairs representing each of the three and August 2004). Therefore, we were able to control clipped sites were plucked by one of the investigators for factors that could potentially influence hair regrowth, (SD), with the necessary caution to preserve the hair such as breed, gender, temperature, day light, diet and structure. Before measuring, the hairs were scrutinized season.7 Inclusion criteria were the lack of systemic or under the microscope to assure that the hair shafts dermatological diseases as evaluated by complete history were intact and straight. From this hair pool, 10 and thorough physical examinations. Blood was drawn primary and 10 secondary hair shafts were mounted in from all dogs prior to the beginning of the study and a microscope slide using a 10-mm wide, double-sided submitted for serum total thyroxine concentrations. Dogs adhesive tape and measured in centimetres from tip to were excluded from the study if serum total thyroxine root with a ruler. The average length of primary and concentrations were below the normal reference range secondary hairs was considered as representative of the for the Veterinary Diagnostic Laboratory at the University sites that were followed up postclipping (lumbosacral of Minnesota and if they were receiving medications area, and right and left lateral thighs). At the end of the that could affect hair growth (e.g. progestins, oestrogen, study, one of the investigators (SD) plucked hairs from androgens, melatonin, glucocorticoids and -thyroxine).
the clipped areas of all 24 dogs. The proportion of hair The study was approved and overseen by the Institu- growth from the original length for each clipped area tional Animal Care and Use Committee of the University was calculated and compared as described previously of Minnesota.
for each group.
Groups and procedures Biopsy collection Twenty-four dogs met the inclusion criteria and were Two skin biopsy samples were collected from the right randomly assigned to three groups of eight dogs each.
lateral thigh from all dogs in groups 2 and 3. One sample All dogs in each group had an area of 6 × 8 cm clipped was collected before and one after the last treatment on the lumbosacral region and both lateral thighs. The to determine whether any dermal inflammation was areas clipped were marked on the dog's skin with a per- induced by brushing (group 2) and whether melatonin manent marker through a template containing a 6 × 8 cm application influenced the hair cycle phases (group 3).
precision-drilled rectangle. The left lateral thigh and the Before treatment, the biopsy sample was collected from lumbosacral area were not treated in any of the 24 dogs.
an area adjacent to the clipped site to avoid inflamma-tion induced by the biopsy procedure influencing hair Group 1. No treatment was administered to the dogs in regrowth of the treated area. After the last treatment, this group. Hair regrowth of lumbosacral area was the biopsy was collected from the treated site. Samples compared to that of left thigh. The right thigh served were collected with a 6-mm punch biopsy instrument as control for the left thigh.
using subcutaneous 2% lidocaine. For group 2, thesamples were sectioned longitudinally to assess dermal Group 2. All eight dogs had the clipped area on the inflammation. Samples from group 3 were transversally right lateral thigh vigorously brushed twice daily for sectioned for morphometric assessment of hair cycle 30 s using a rubber brush (Zoom /Groom®, Kong phases. Skin biopsy samples were routinely processed Company, Golden, CO, USA) for the 2-month study for histopathology and stained with haemotoxylin and duration. Based on a pilot study, the brushing period eosin stain (H&E).
was shown to induce the desired mild skin irritation.
The left lateral thigh served as control. Hair regrowth between the right and left thighs and between the To assess the degree of dermal inflammation in group lumbosacral area and the left thigh was compared.
2, all inflammatory cells present within the dermis ofthe whole tissue section were counted at ×40 magnifi- Group 3. All eight dogs had the clipped area on the cation. In fields containing glands and hair follicles, only right lateral thigh treated with a compounded solution intervening dermal regions were counted. Intravascular 2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology

Body site, melatonin and brushing effect on hair regrowth and fibroblastic cells were excluded from the count.
The degree of inflammation was classified as 0 – absent;1 – low (< 10 inflammatory cells/section); 2 – medium(10–50 inflammatory cells/section); or 3 – high (> 50inflammatory cells/section). The investigator per-forming the counting (SD) was blind, regarding whetherthe histopathological section referred to before or afterbrushing.
Morphometric assessment of hair follicle cycle phases Figure 1. Average percentage of hair regrowth 2 months after
in group 3 was performed in transversally sectioned clipping the lumbosacral area and left lateral thigh of 24 normal Siberian Husky dogs. Primary and secondary hairs were evaluated. skin biopsies as previously described.21,22 Briefly, 40 –50 LSP = lumbosacral area, primary hairs; LTP = left thigh, primary transversal sections per biopsy sample were initially hairs; LSS = lumbosacral area, secondary hairs; LTS = left thigh, reviewed to select follicular units showing sebaceous secondary hairs. *Significantly (P = 0.002) different from LTP. glands and arrector pili muscle. The presence of these †Significantly (0.026) different from LTS.
structures indicated that the hair follicles were sectionedat the mid-isthmus level, which allowed the determina-tion of the hair follicle phases.23 A follicular unit wasdefined as a group of three compound follicles.21,23Anagen and telogen hair follicles were counted in fivefollicular units per biopsy sample.21 The investigatorperforming the counting (SD) was blind, regardingwhether the histopathological section referred to beforeor after melatonin treatment.
Figure 2. Average percentage of hair regrowth after 2 months of
Paired Student's t-test was used to compare the pro- clipping the left and right lateral thighs of eight normal Siberian portion of hair regrowth postclipping between the lum- Husky dogs. The right lateral thigh was also brushed twice daily for bosacral area and the left lateral thigh on all 24 dogs.
the 2-month period. Primary and secondary hairs were evaluated. RTP = right thigh, primary hairs; LTP = left thigh, primary hairs; Paired Student's t-tests was also used to compare the RTS = right thigh, secondary hairs; LTS = left thigh, secondary proportion of hair regrowth between the brushed thigh hairs. No significant difference was found between RTP and LTP (right) and the control thigh (left) in group 2, and (P = 0.84) or between RTS and LTS (P = 0.40).
between the melatonin-treated thigh (right) and thecontrol thigh (left) in group 3. Wilcoxon signed rankstest was used to compare the score given to dermal and brushing the right thigh was 3.20 and 2.46 cm, inflammation before and after brushing the right leg of and after only clipping, the left thigh was 3.10 and the eight dogs in group 2 and to compare the proportion 2.21 cm, respectively. No significant difference was of anagen follicles before and after melatonin treatment found in the proportion of primary (P = 0.84) or of the eight dogs in group 3. A value of P < 0.05 was secondary (P = 0.40) hair regrowth when the brushed considered significant. All analyses were preformed thigh (right thigh) was compared with the control thigh using    (SAS Institute, Cary, NC, USA).
The average length of primary hairs before and 2 months after clipping and treating the right thighwith melatonin was 3.80 and 2.15 cm, and after only clipping, the left thigh was 3.8 and 2.09 cm, respect-ively. The average length of secondary hairs before and The average length of primary hairs before and 2 months 2 months after clipping and treating the right thigh after clipping the lumbosacral area was 5.70 and with melatonin was 3.00 and 2.36 cm, and after only 2.95 cm, and the left lateral thigh was 3.30 and 2.10 cm, clipping, the left thigh was 3.10 and 2.26 cm, respect- respectively. The average length of secondary hairs ively. No significant difference in the proportion of before and 2 months after clipping the lumbosacral primary (P = 0.52) or secondary (P = 0.15) hair regrowth area was 4.40 and 2.79 cm, and the left lateral thigh was was seen when comparing the melatonin-treated thigh 2.80 and 2.03 cm, respectively. Proportionally, primary (right thigh) with the control thigh (Fig. 3).
(P = 0.002) and secondary (P = 0.026) hairs were sig- Before brushing in group 2, the degree of dermal nificantly longer on the left lateral thigh compared to inflammation was low in one dog and medium in seven the lumbosacral region 2 months postclipping (Fig. 1).
dogs. Two months after twice-daily brushing, the degree The average length of primary hairs before and 2 of dermal inflammation was low in one dog and medium months after clipping and brushing the right thigh was in six dogs. These differences were not significant (P = 3.50 and 2.35 cm, and after only clipping, the left thigh 1.00). Dermal inflammation could not be assessed in was 3.50 and 2.38 cm, respectively. The average length one dog postbrushing because of poor tissue process- of secondary hairs before and 2 months after clipping ing. In group 3, no significant differences were observed 2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology

SF Diaz et al. region should have been proportionally longer than,or at least comparable to, the lateral thigh at 2 monthspostclipping. However, the findings of the presentstudy did not confirm it, indicating that factors otherthan hair length may dictate the rate of hair regrowthin at least some body sites.
Although the factors influencing hair follicle cycling and hair growth are not completely understood, increase Figure 3. Average percentage of hair regrowth after 2 months of
in blood supply seems to be important in initiating clipping the left and right lateral thighs of eight normal Siberian anagen.5,7 Angiogenesis and increased skin perfusion Husky dogs. The right lateral thigh was also treated twice daily with 0.1% melatonin solution for the 2-month period. Primary and have been observed in association with active hair secondary hairs were evaluated. RTP = right thigh, primary hairs; growth in mice and rabbits.25 Consistent with this, hair LTP = left thigh, primary hairs; RTS = right thigh, secondary hairs; loss has been observed in people in areas affected by LTS = left thigh, secondary hairs. No significant difference was occlusive arterial disease.26 In dogs, decreased perfusion found between RTP and LTP (P = 0.52) or between RTS and secondary to localized vasoconstriction in shaved skin LTS (P = 0.15).
sites has been proposed as the pathomechanism offollicular arrest during postclipping alopecia.10 in the average proportion of anagen follicles before Topical sensitizers have been used in humans to (50.3%) and after (58.8%) 2 months of topical melatonin induce dermal inflammation and hair growth with treatment (P = 0.67).
variable degrees of success in patients with alopeciaareata, alopecia totalis and alopecia universalis.27 Indogs, anecdotal evidence exists that hair regrowth can D I S C U S S I O N
be induced at the sites of skin biopsy9 after vigorousbrushing, or where there is severe skin irritation, sug- In this study, the hairs on the lumbosacral region were gesting that induced inflammation also stimulates hair proportionally shorter than on the lateral thigh at regrowth in this species.10,12 In this study, vigorous 2 months after clipping normal Siberian Husky dogs.
brushing performed twice daily for 30 s each time Moreover, brushing and topical melatonin had no did not influence hair regrowth on the lateral thigh.
impact on hair regrowth postclipping.
The irritation caused by brushing did not induce suffi- Hair growth is a very complex phenomenon influ- cient dermal inflammation and may have not been enced by many endogenous and exogenous factors.
enough to cause stimulation of the hair follicles. In Endogenous factors include cytokines and growth people treated with topical sensitizers for alopecia regulators. Important exogenous factors include pho- totalis and universalis, an active dermatitis characterized toperiod and temperature.5–7 These environmentally by erythema and scaling was required to induce hair related factors influence the secretion of melatonin growth.26 Future studies investigating a different brush- and prolactin, which in turn control the annual cyclical ing protocol or other modes to induce skin irritation activity seen in hair follicles.14 Although hair growth are warranted.
and replacement have been studied in detail in humans, In a recent study, topically applied melatonin was sheep and laboratory rodents, very few studies have shown to promote hair growth by increasing the anagen been published for dogs and cats.1–4 rate in women with androgenic alopecia or diffuse Linear measurements of the hair shaft have been alopecia.20 In this study, melatonin applied topically performed to assess hair growth.15,24 Using this method, twice a day did not induce anagen, as determined by we found that the hair length on the lumbosacral area morphometric analysis of cross-sectioned hair follicles.
at 2 months postclipping was proportionally shorter Siberian Husky dogs with no hair coat abnormalities than that on the lateral thigh. In 1983, Gunaratnam were intentionally included, but it is possible that and Wilkinson performed a study in cross-bred male abnormalities in the hair follicle cycle are necessary for dogs and showed that different body sites have differ- melatonin to be effective. It was observed that as the ent rates of hair growth.3 When comparing three body hair started to regrow, it became difficult for the mela- sites (forehead, shoulder and flank), they found that tonin solution to reach the skin, and it is possible that those hairs in which the final length was greater grew this prevented the melatonin solution from being faster.3 This would indicate that the speed of hair absorbed. Alternately, the concentration and frequency growth was related to the final length in each particular of administration and /or the vehicle used may not have site. In this study, the rate of hair growth was not invest- allowed the adequate absorption of melatonin. The igated, making a direct comparison with Gunaratnam concentrations of melatonin in the skin or blood were and Wilkinson's findings difficult. The average hair not assessed in this study to test these hypotheses.
length of primary hairs before clipping the dogs was In conclusion, the results of this study showed that 5.7 cm on the lumbosacral area and 3.3 cm on the in normal Siberian Husky dogs, the hairs on the lum- lateral thigh. Therefore, if the hair growth rate is truly bosacral region were proportionally shorter than on faster in body sites with longer hair shafts, it is reason- the lateral thigh at 2 months postclipping. These find- able to expect that the hair length on the lumbosacral ings indicate that it takes longer for the hair to regrow 2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology Body site, melatonin and brushing effect on hair regrowth to its full length on the lumbosacral area, supporting their response to prolactin and melatonin. Journal of anecdotal reports. However, future studies are needed Anatomy 1994; 185: 135 – 42.
to substantiate our findings and to explain the differences 14. Forsyth IA, Gebbie FE, Arendt J. Timing of melatonin in hair regrowth according to body sites. Additionally, treatment: differential effects on oestrus and coat growth our study could not demonstrate that induction of in goats. Animal Science 1997; 65: 267–73.
15. Santiago-Moreno J, Lopez-Sebastian AA, del Campo A dermal inflammation stimulates hair regrowth because et al. Effect of constant-release melatonin implants and the brushing protocol used was not adequate to cause prolonged exposure to a long day photoperiod on prolactin significant dermal inflammation. Finally, topical mela- secretion and hair growth in Muflon. Domestic Animal tonin at the concentration and frequency used in this Endocrinology 2004; 26: 303 –14.
study did not increase the numbers of anagen follicles 16. Paradis M. Melatonin therapy for canine alopecia. Kirks in healthy Siberian Husky dogs as others have observed Current Veterinary Medicine. Philadelphia: W.B. Saunders, in women with alopecia. Future studies need to be 2000: 546 – 9.
conducted to determine if topical melatonin increases 17. Paradis M. Canine recurrent flank alopecia: treatment anagen rate in dogs with various types of alopecia.
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2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology SF Diaz et al. Les buts de cette étude étaient de déterminer l'influence de la zone cutanée, d'un borssage vigoureux et de l'application topique de mélatonine sur la repousse pilaire chez les chiens normaux après tonte. Des Siberianhusky ont été regroupés au hasard en trois groupes de huit chiens. Tous les chiens ont été tondus sur la zone dor-solombaire et sur la face postérieure des cuisses. La cuisse gauche et la zone dorsolombaire n'ont pas reçu detraitement, et ont été comparées chez les 24 chiens. Huit chiens ont eu la cuisse droite traitée par l'applicationbiquotidienne de 0.1% melatonine pendant deux mois et la repousse a été comparée avec l'autre cuisse. Huit chiensn'ont pas eu de traitement sur les cuisses. Huit chiens ont eu la cuisse droite brossée deux fois par jour pendantdeux mois.
Les poils étaient épilés avant et deux mois après la tonte et la proportion de pousse pilaire a été calculée. Des biopsies cutanées ont été réalisées avant et après le traitement pour déterminer si le brossage provoquait uneinflammation et si la mélatonine provoquait une augmentation des poils en anagène. Proportionnellement, lespoils de la cuisse gauche étaient significativement plus longs comparés aux poils de la zone dorso-lombaire deuxmois après la tonte. Aucune différence significative n'a été observée entre les cuisses non traitées et les cuissesbrossées ou traitées par la mélatonine. Aucune différence significative n'a été observée pour le nombre de poilsen phase anagène. Nos résultats montrent que les poils de la zone lombo-sacrée sont proportionnellement pluspetits que ceux des cuisses deux mois après tonte. En outre, la mélatonine ou le brossage n'influencent pas larepousse pilaire chez les chiens normaux.
El propósito de este estudio fue determinar el impacto de la localización corporal, el cepillado vigoroso y la aplicación de melatonina tópica en el crecimiento del pelo tras rasurado en perros normales. PerrosHuskies Siberianos se asignaron de forma aleatoria en tres grupos de ocho perros cada uno. Todos los perrosfueron rasurados en la región lumbosacra y el lateral de los muslos. El muslo izquierdo y la zona lumbosacra norecibieron tratamiento y se compararon en los 24 perros. Ocho perros recibieron tratamiento con 0.1% demelatonina dos veces al día durante dos meses en el muslo derecho, y el crecimiento del pelo se comparó con eldel muslo izquierdo. Ocho perros fueron cepillados dos veces al día durante dos meses en el muslo derecho, y elcrecimiento del pelo se comparo con el lado izquierdo. Ocho perros no recibieron ningún tratamiento. Algunospelos fueron arrancados antes del rasurado y dos meses después del mismo, y la proporción de crecimiento delpelo respecto la longitud original se calculó y comparó tal y como se ha descrito. Se tomaron biopsias antes ytras el tratamiento para determinar si el cepillado producía inflamación dérmica y si la melatonina incrementabala proporción de pelos en fase anagénica. Proporcionalmente, los pelos del lado izquierdo fueron significativa-mente más largos que los de la región lumbosacra dos meses tras el rasurado. No hubo diferencia significativaentre los laterales de las extremidades tratados con melatonina o cepillado y los no tratados. No se observó unadiferencia significativa en la proporción de pelos en fase anagénica antes y tras el tratamiento con melatoninatópica. Nuestros resultados demuestran que los pelos de la región lumbosacra son proporcionalmente mas cortosque los de los muslos dos meses tras el rasurado. Y lo que es mas, el tratamiento con melatonina topica y el cepil-lado no influyeron en el crecimiento del pelo tras el rasurado en perros normales.
Die Ziele dieser Studie waren es, die Auswirkung der Körperregion, sowie von kräftigem Bürsten und topischer Behandlung mit Melatonin auf das Nachwachsen der Haare nach dem Scheren von nor-malen Hunden zu eruieren. Sibirische Huskies wurden zufällig in drei Gruppen von je acht Hunden eingeteilt.
Bei allen Hunden wurde die Lumbosakralregion und die beiden lateralen Oberschenkel geschoren. Der linkeOberschenkel- und die Lumbosakralregion wurden nicht behandelt und bei allen 24 Hunden verglichen. Bei achtHunden wurde der rechte Oberschenkel mit 0.1% Melatonin zwei Monate lang zweimal täglich behandelt unddas Nachwachsen der Haare verglichen mit dem des linken Oberschenkels. Bei acht Hunden wurde der rechteOberschenkel zwei Monate lang zweimal täglich gebürstet und das Nachwachsen der Haare verglichen mit demdes linken Oberschenkels. Bei acht Hunden wurde weder der eine noch der andere Oberschenkel behandelt.
Vor und zwei Monate nach dem Scheren wurden Haare ausgezupft, die Proportion des Haarwuchses von derOriginallänge kalkuliert und verglichen wie oben beschrieben. Biopsieproben wurden vor und nach der Behan-dlung entnommen, um festzustellen, ob das Bürsten eine dermale Entzündung verursachte und ob Melatoninden Anteil an anagenen Haarfollikeln steigerte. Zwei Monate nach dem Scheren waren die Haare des linkenOberschenkels im Verhältnis signifikant länger im Vergleich zu den lumbosakralen Haaren. Kein signifikanterUnterschied beim Nachwachsen der Haare wurde zwischen den nicht behandelten und den mit Melatonin behan-delten oder gebürsteten Oberschenkeln gefunden. Es bestand kein signifikanter Unterschied bei der dermalenEntzündung vor und nach dem Bürsten. Keine signifikanten Unterschiede wurden beim Anteil an anagenenHaarfollikeln vor und nach der topischen Behandlung mit Melatonin beobachtet. Unsere Ergebnisse zeigten,dass die Haare in der Lumbosakralregion zwei Monate nach dem Scheren verhältnismässig kürzer waren als dieHaare der lateralen Oberschenkel. Außerdem hatte weder die topische Melatoninbehandlung noch das Bürsteneinen Einfluss auf das Nachwachsen der Haare nach dem Scheren normaler Hunde.
2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology

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