J . vet. Pharniacol. Thprap. 9.40-48, 1986.

Dermal reactivity to histamine, serotonin and bradykinin in relation to allergic skin reactions of the horse ALEX MOKKOW, PATKICK.]. Q U l N N lk KENNE'I'H 1'. BAKEK

Faculty of Veterinary Medicine, University College L)iil)liii, Veterinary <:allege, lkillsl~ridge, Dublin. Ireland

Morrow, A., Quinn, P.J. & Baker, K.P. Dermal reactivity to histamine, serotonin and bradykinin in relation to allergic skin reactions of the horse.]. vet. Pfiaimarol. Therap. 9, 40-48.

The reiictivity 01' horse skin t o ititriidertiial inociil;itioii ol' histaiiiiiie, serotonin ;id I)ratlykiniii wiis investigated, iiiitl the resultiiig reactions c o t i i p i i w l witli those produced in the siiiiie horses h y ;I 1 % whole-body exti'iict of ( d ' ~ ~ / i l ' i ~ i d i %

Both histmiine and bratlykiniii proditcetl large re;ictions, I N I I there iv;is no sigiiiticant correlation between the tleriiial respoiisiveiiess t o insect allergeii ;iiitl either histaiiiiiie or Imatlykinin. T w o ;ititi-liist~iiiiiiie tlrugs (I)i'oiiietli;iziiie hytlrochloritle and ti~ipelenii~iiiiiiie hytlrocliloritle) were elltctive in i.etluc:itig the reaction produced by the insect extract. A . M o ~ w r o , Crrflw / i J r Tt.o$ic.rt/ Volrrirr~rty Mrdicitlo, Emlrr H ~ I , RdIt t , hfid/oI/f~utt EH25 9RG, U.R.

T h e occurrence of' histaniine in aniiiial tissues w a s lirst reported by Wiiitl;ius lk Vogt (1!)07), anid its iiivolveiiient in ;iliaphylaxis by Dale (1913) . Katz lk Coheii ( 194 I ) discovered that the atltlition of antigen t o I>lootl of atopic subjects released 1iist;iiiiine. I t has since lieen shown that m i s t cells mtl Ixisophils synthesize ;iiicl/or release ;I variety of sul)stiinces knowti collectively as the chetiiical iiietliators of immediate-type hypersensitivity. Species dit- ltrences i n tlie types 01' tiiecliators involved in ;inaphylactic reaciions occiir, and even when the iiiediators are the siiiiie, the sensitivity of tlie target organs in various species is tlilf'er- eiit (Lichteiistein id id., 1979). Lxucocytes isolated I'roiii sensitized horses Iiave been shown to release Iiistaiiiine i q m i incubation

*Sigma Chemical Company, Si Louis, MO, U.S.A.

with the sensitizing aiitigeii (Btirka 111 nl. , 1976).

I n this study, the elltcts of' various conceii- ti-ations 01' histamine, serotonin m t l l ) ~ ~ c l y - kinin on horse skin were ex;iniinetl, and the response compared with that produced when an insect allergen was used in intradermal skin tests on the same horses. The el'fect o f two anti-histamines on the reaction produced by the insect extriicts wiis also investigated.

MATE K I A LS AND METHODS

40

Mediulors of ullergic skin reucliuru in the horse 41

in isotonic saline immediately prior t o use. Skin tests were carried o u t wi th these clilutioiis of' ;ill three nietliators Ijy tlie iiitriiderinal iiiociilatioii o f 0 . 1 nil i i t previously iiiarketl sites in the mitltlle ot' tlie lateral aspect ot' tlie neck using ;I 26-g neetlle its previously re- ported (Qiiinn />/ d., 1983). Reactions were recorded by nie;isiiriiig the skin-fold thickness iii iri,jection sites prior to, and at 20 min, ;ind 1, 4, 24 antl 48 h after challenge using verniei- ciillipers. Six h o i x s , live appirently nornial horses ;inti one horse (Horse I.) which I i x l ii

history o f allergic skin re;ictioiis, wi th annii;tl recurrence of lesions typicill of sweet itch, were each challenged with all three s u b - stances. .I'he live norni;il horses failed t o develop lesions i n tlie tieltl over t w o se;isons w h e n exposed t o the same insect c1i;illenge iis

Horse '1'. Tests with the three mediators in any one horse were perlimned at different times.

Wliole-l)otly extriicts 01' C/d i~~i i l / ) . \ were pre- pired iis previously clescrilietl (Qiiiiiii P/ d., 1983). All six horses were cliallengetl intraderinally wi th 0. I nil of ii 1 % (w/v) insect extract in isotonic saline antl a n isotonic saline control. 'l'lie reactions were recorded by nieasui-ing the skin-tidtl tliickness at the clial- lenge sites.

Intr~1~1er111~il skin tests were c;irrietl out OII

three Iiorses which previoiisly gave large reactions t o challenge with insect extriicts. Following anti-Iiistaniine treiitment, c1i:iIlenge with extracts of'C/tlirfJi~/e\ was carried out . The ~inti-liist;tmines used were ~>i~~iiietli;inine h ytlrochloricle (Phenergan') and tripelenna- mine liytlrocliloritle (Vetil~en~~iiiiiiiet). Both were given iis ;I single intriiiiiuscular injection at the reconiniencletl dosage rate: pi.ometIi;i- Line hyclrochloritle (500 ~ng/ml), l.5520 iiig/kg

* M a y m t l Ihkcr Lttl, Dageiiliani. Essex. U.K. tCXxi-(kigy Lrtl. Uiisel. Swiizerliintl.

body-weight; tripelennamine hydrochloride (20 rng/ml), 0.5 mg/kg body weight. Horses T antl 5 both received prometliazine hyclro- chloride first, and Horse X received tripelen- iiarnine hydrwhloricle lirst. l'lie tests in any one horse were sepiratecl by iit least 1 week. Following an interval of ,30 min afier each treatment, the horses were cliallengetl intraclermally with 0 . 1 % (wlv) whole-ldy extracts of'Cidirciide.\, histamirie (5 mg/ml), ;ind a n isotonic saline control. The reactions were recorded as the increase in skin-li)ltl thickness iit the challenge sites.

R E S U 1.T S

The reactions that tleveloperl i n all six horses following challenge with histaniine, serotonin and bradykinin are shown in Fig. I , Fig. 2 ;rnd Fig. 3, respectively. The reactions piwlucetl by histaniine in the six horses 20 min after challenge were conceiitr~ition-del,eiitlellt. The niaximuni recorded values o f these reac- tions occurred at either the 20-niiii or 1-11

reading (Fig. 1). While the reactions produced by braclykinin were smaller than tliose pro- duced by histaniine, they also teiitletl to increase in size with increasing concentriition. The inaxiniuni recorded values ol ' these reac- tions were the 20-min readings, except IOr Horse 8, where the 1-11 readings were Iiirgest Iiw all concentrations, antl Horse 5, i n whicli the reactions proclucecl by a concent~.iition of I nig/nil were largest at the 1-11 re;itling (Fig. 3). The reactions produced by serotonin were much smaller than those produced by the other two mediators aiitl bore little re1;i- tionship to the conceiitration used.

The increases in skin-foltl thickness 20 inin after challenge for all three metliators iit ii

concentration of' 1 mg/ml aiitl tlie isotoiiic saline control are sliown in 'l'able I . Applica- tion t o this data of ;in analysis of' v;irimce inodel for two-txtor stutlies, where there is only one observation per treatment ;is tles- cribetl by Neter 8c Wasseriiiiin (1974), reveiils the presence o f sigiiiticaiit tre;itiiient el'l'ects (P < 0.001). The aii;ilysis hiled t o support the hypothesis that the Iiorses tlit'feretl sigiiil'i- cantly in their i q m i s e t o the wrious niecliators (horse effects: 0. I > I' > 0.05). However, using the Tukey one degree 01'

Horse 9

l'1

Horse 7 "1

Horse 8 O l

" ,L i,' 1 A,... -.. ..... *-..... ;L if!....... ... -- -\ ......... 5. *...>, -. "i .-. \ . %... ...> .... E

v) ... a. ......

5 s

- 6

0 '+ 5 4 "-..., 4

....... ....... v) 6 d" -...... ....... .-

L7T7+ma Time a f t e r challenge ( h )

Horse T

L T ? e 7 8 Time a f te r challenge (h)

L - 7 k 7 " Time a f t e r chollenge ( h )

....... 10.0 mg/ml i-m

Time a f te r challenge ( h )

:I." Time a f t e r challenge ( h )

Horse 3

S.

I L m a Time a f te r challenge (h)

FI (;. I . 'I'lie results of iiitriidertii:il challenge (it six horses (live nortiiiil Iicirses: tlorses 7 . 8. 9. 5 ;itid 3. ; i t d

one allergic horse, Horse T) with various coticeiitratiotis (11- Iiistiunitir. ; i i d nortn;il salitie. 'l'lie rexriotis \\tw rerortletl b y me;isuritig the skiii-fi)ltl thickness i l l injection sites prior lo. iiiitl ;II 20 iniii. I . 4. 24 i ~ n d 4X 11 i11'1rr. cli;illeiige.

t'reetloiii test, highly significant ( P < 0.00 1) interaction el'tects between tlie t w o fiictors tiiicler sttrtly (horse eft'ects and treiitiiieiit

et'fects) weIe also shown to be present. When interactions ;ire present. the mialysis of' variaiice iiiotlel is ii1oi.e likely to fail t o disclose'

treiitiiieiit) t h i anticipated ( N e w lk Wiisser- iiiiiii, 1974). Since highly signilicaat t reatiiieiit

the Iiresellce of I.e;ll filctor el'fkcts (Ilorse or

effects m c l interaction effects occiirrecl, this woiild seem t o iniply that horse effects were also present. While Horses 3, 'I. aiitl 9 tended to produce larger reactions th;in the other three horses, this was p;irticularly ni;irkecl iii

their response to histaiiiitie. Horse 3 ;t i id

Horse T a l s o ~irotlucetl quite large reactions t o bradykinin.

The increases in skin-fold thickiiess 'LO i i i i i i

Mediulors of ullergic skin reuclioru in the horse 43

.... .............. - 0 z- i. =%=? 41- c-=

------------;- ................... ....... ".....".I -..a apt

Time after challenge (h)

Time after challenge (h)

Horse 8

'1 '1

Sulm c-0 0.01m(/ I - 0.1 w m l ....... 1.0 y / m t ---

10.0 mg/ml ....a

Horse 9

----------,--_ ............. .................... 0b-o

4 k".. ...................................

3 r

----------,--_ ............. .................... 4 k".. ................................... r---

Time a f te r challenge (h) Time after challenge (h)

Horse 7

Time a f te r chollenge (h)

Horse T

'"1

/--- '.,---- .-*--- 'r ........................ :+ .......

31

2! 1 2 3 4 ' m s Time a f t e r challenge (h)

FIG. 2. The results of intradernial challenge of six horses (five normal horses: Horses 7, 8, 9, 5 and 3, and one allergic horse, Horse T) with various concentrations of' serotonin, and nornial saline. The reactions were recorded by measuring the skin-fold thickness at injection sires prior to, and at 20 niin, I , 4.24 and 48 h after, challenge.

m t l I , 4 atid 24 ti f'ollowing ch;illenge of all six horses with i i n extract of' Cdic.oiclcv are showii in Tal,le 11. The reiictioiis produced by the isotonic saline control were siniilar t o those Iiroducecl ;it the previous challenge, with no site showing i in increase in skin-loltl thickness of' iiiore than 1.2 iiitii at the 20-miti ieiirling. The 2O-iiiin reactions piwluced in a11 six horses by histaliline ;ind Imclykinii i ;it ;I

c-oncentration of' 1 nig/iiil were coiiip;riwl with the reactioiis pi~odiicerl wheii the horses were ch;illeriged w i t h whole-body extracts 01' Cri l i - c.oide\. N o significant correl;ition wiis l0 i i i i t l

between the response t o iiitracleriiial chill-

lenge with the extixt of' Ciilicoidcc. ;iiitl liista-

mine ( r = 0.6; P > 0.1) or br;itlykiniii ( r = 0.5: P > 0.15).

The increase in skin-li)ltl thickness ;it sites on a11 three horses t i w t e c l with both anti- histamines 20 riiiii mid 1, 4 mid 24 ti d ter challenge with i i n extract 0 1 ' O'rrlicoidev or ii

histamine control are showii in 'l.:il)le I l l . Both treattileiits appear t o have suppressed the reactions produced b y the extracts ol' Cirlicoicles 20 niin and I , 4 iiiitl 24 11 a1'1er ch;illetige, coiiiparetl with the lactioils pro- duced wlieii the iuiim;ils were not ttwitetl with anti-liist;iiiii~~es. Proiiieth;izitie \v' ..ioi.e

effective than tripelenii;iiiiitie iii suplmssiiig the reactions produced b y the extract 01'

Horse 3

:I 6

2 . " 0 1 2 3 4 - 2 4 46

Time after challenge (h )

C .- * fJ-I

a .

Horse 8

wim m 0.01 mom1 - 0.1 mwml 1.0 q l m l ---

10.0 mpiml I..- .......

z L i i i Time after challenge (h )

Horse 5

I1

'I 2 "

0 1 I 3 4 - 2 4 48

Time after challenge ( h )

Horse 9 17

...... "'.a.

................. ................

'1 '!a i i i i1-s

Time a f te r challenge (h)

'8

Time ofter challenge (h)

Horse T

l1A----Sm

........... ......

?!a 1 2 3 4 f C a

Time o f te r chollenge ( h )

FIG. 3. The results of intradermal challenge of six horses (five normal horses: Horses 7, 8, 9, 4 and 3, and one allergic horse, Horse T) with various concentrations of bradykinin, and normal saline. The reactions were recorded by measuring the skin-fold thickness at injection sires prior to, and at 20 min, I , 4.24 and 48 h after, challenge.

TABLE I. Reactions produced by intradermal challenge of six horses with three possible mediators of immediate-type hypersensitivity and an

isotonic saline control

Horses challenged

Challenge substance 7 8 T 9 3 5

Histamine Serotonin Brady kinin Saline

2.4 2.8 5.1 4.9 5.3 2.6 0.4 0.4 0.3 0.2 0.G 0.6 1.2 1.5 I .8 1 .0 2.5 1 . 1 0.2 0.3 0.3 0.2 0.6 0.4

Analysis of vuriunre F P Factor A (treatment effects) 37.452 < 0.001 Factor B (horse effects) 2.323 0.1 > P > 0.04 Tukey one degree of freedom test 4 I .75 < 0.001

The data refer to the increase in skin-fold thickness (mm) at in.jection sites 20 min after challenge.

TABLE 11. Skin reactions 20 min, 1, 4 and 24 h fdlowing intradernial challenge with a I%, whole-body extract of Culiroides

~ ~~~

Horses rhallenged

Time alter challenge 7 8 9 T 5 3

20 min I 11

4 11

24 h

~ ~

1.6 1.3 1.7 4.8 2.4 2.9 2.1 4.9 1 .fi 8.3 3. I 2.8 3.6 8.8 I .4 14.9 11.5 5.4 0.9 I .8 0.1 6.0 I .4 I .9

The values refer to the increase in skin-fold thickness (mm) a1 injection sites.

'TAli1.F. 111. Keartions (increase iii skiti-fold tliicktiess in inm) protluretl 20 ii i i i i . I . 4 i i i i t l 24 11 alter i~iirii~leriiial clialleiige of tlirer Iiorses wit11 i i I % exir;ict of (;rr/ic.oir/c<r and ;I hisi;iiiiiiie (5 nig/inl) control lollowing treatment w i t l i i \ v o ;iiiti-liisi;iiiiiiies: ~~roiiie~liiiziiie Iiyclroc-liloritle

i i n d tri~~eleiiiiiiiiiiiie hyclrochloritle

Histaiiiiiic 20 mill I I 1

4 11

24 I1

I .(i 2 . I 9.8 (i . (i

4.4 4.7 3.6 I .2

0.4 O.(i 2. I I .o

4.6 X i 2 . i 0 . i

0.2 0.3 2.3 0.5

I .4 2. I x. 7

I I .!I

6.4 i.!) 6.i 2.0

I .!) 2.1) 5.4 I .:I

(i.2 f i . 0 i.9 I .(i

0 . 2 0.4 3.(i 0.i

4.X 5.2 t i . I 0.9

DISCUSS I O N

f'ailetl to elicit any nieastir;il)le skin response wit l i i t i the close range 0.025-200 pg. While the tiiilure of' serotonin to p d u c e more clefinite reactions tiiiist indicate that i t is of' rloul)tl 'ul sigiiiticmce in allergic skiti reactions 0 1 the horse, it n i a y still be rele;ised during iiiitiietliate-type hypei-sensitivity re;ictions. Wells 8c E y e (1970) reported t h i i i the tliresliold for I)ltieiiig 1i)llowiiig iti~riic1eim;tI

rli;illetige with serotonin in ~ i l v e s t l ia t h;id Ixen previously ii+xtecl int i - i iwtioi ts ly w i t h dye was 0.8 pg. Howe\vr , I;irger doses of' serotonin (> X pg) (lid not produce i i t iy b lue lesions. 'l'liey suggest 11i;it this liiilirre ol ' serotonin t o iiicrease capill:iry periiie;ilditv m a y have Ixen clue t o ;I precloiniii;ttit arterio- lar coiisti.ictor el'l'ert ;it the Iiiglier (lose YAW.

46 A. Morrow, P. J . @inn &? K . P . Hnkrr

The ability o f serotonin to produce rapid contraction of snitn)th muscle, vasoconstric- tion and increased vascular permeability .varies from species to species (Walton, 197 1).

Kiek ( 1955) found increased bloocl Iiista- mitie levels during the siiniiiier months in horses susceptible to Queenslantl itch. Cutaneous reactions to insect allergens in man are not accompanied by increased blood hista- mine levels (Kaplan rl d.. 1977). Zanzucchi ( 1942) reported that elevated blood histamine levels occur in emphysematous horses, but Eyre (1972a) was unable to confirm this. How- ever, Eyre (1972a) found elevated plasma serotonin concentrations in 46% of emphysematous horses. None of these ani- mals showed increased blood kiniii activity (Eyre 8c Lewis, 1!)73), although elevated con- centrations of histamine antl kinins were f0und in the plasma o f horses cluring acute anaphylaxis. The systemic ef'fects of hista- mine, serotonin and brarlykiniii in the horse have been described by Eyre 8c Lewis (1973). They reported that brxlykiiiin wiis the most potent o f these three iigoiiists in the horse.

Kiek (1954) reported that, in relation to Queensland itch, non-susceptible animals showed a lower activity to intraderinally in- jected Iiistmiine than did tlie susceptible ones. While the reactions to the various mediators in this study varied ftom horse to horse, they could not lie related t o the occurrence of' sweet itch or the skin reactions t o insect ;illergen 1i)untl in nornial horses. Horse 'f', the only horse with ;I history of' sweet itch attacks in the group, produced tlie largest re;iction 1i)llowing challenge with iusect extract, but some of' the noriii;il horses a l s o resliondetl quite strongly. Analysis of' the results fiiiletl t o show significant correlatioiis betweell the re- sponse t o histamine atid that to insect ;illergen, or the response ~)rotlucetl by I ~ i t l y - kinin antl insect allergen. ' I h re;ictions pro- duced Iiy histaiiiine ;ind Iiriitlykinin iii Horse 'I' were quite large, h i t some ot' tlie other I io ixs ~)ro(lucetl reactions o f ;I siiiiil;w size. Oliel 8c Schmiterliiw ( 1!)48) reported t h a t eiiiphyseiii;ito~is horses, like Iiutii;in itsth- niatics. show increased sensitivity t o hista- inine, iiritl that iiljectetl hist;iniine induced most of' the symptoms 01' 'heiives'. However, Eyre XC Lewis ( 1 973) repwtetl t h a t tliei-e appeiired to be no tlil'ference in sensitivity t o

intravenously injected drugs, histamine, serotonin or bradykinin, between antigen (whole bovine serum) sensitized antl non- sensitized horses. These results relate t o artificially sensitized animals ;tiid not to cases o f naturally occurring hypersensitivity.

Based on attempts t o suppress experinient- ally induced systemic anaphylaxis in tlie horse using anti-histamines and non-steroiclal anti- inflammatory drugs, Eyre ( 1976) suggested that histamine antl serotonin are of relatively low significance in equine anaphylaxis, wliere- as kinins, prostaglandins antl slow-reacting substances of anaphylaxis may be more ini- portant. He concluded that, while aniines seem to initiate the observed early phe- nomena, the non-aniine substiinces may lie more significant overall than the aniines in tlie mediation of equine hypersensitivity (Eyre, 1976). Willianis 8c Morley (1972) reported that prostaglandins potentiate the effect of histamine and bradykinin injected intraclerni- ally in the guinea-pig. The potentiation, which was greater with combinations of brdykiniri and prostaglandins than with histamine antl prostaglandins, failed t o prolong the re- sponse. Spector 8c Willoughby ( 1964) sug- gested that histamine is probably of import- ance only in initiating anaphylactic changes, and that other mechanisms are sulxequently necessary for the perpetuation ot' the re;ic- tions. The low yield of histamine f'roni antigen-challenged sensitized equine leuco- cytes reported by Burka rl ( I / . (1976) supl)orts the view that histamine is o f less importance i n hypersensitivity in horses conil)airtl to sonie other species.

Kesults of'the skin test carried out on three horses following treatment with t w o tlil'l'erent inti-liistaniiiie drugs on separate occasions show that Iloth were effective in recliicing the skin reactions t o extracts of' Crt/icoirlev. How- ever. iis the tests following treatnient w i t h anti-liistaiiiitie drugs and previous active tests were pdimnetl a t tlitl'erent times, ;ind [lie o~itcome of' any set of tests is ~iroiialily to sonie extent ;iffectetl by previous tests, tlie ch;iiige in skin reactivity iiiay have resulted I'roni ;I nuniber of' contriliuting f'ktors, inclutliiig the ~iiiti-liist~iiiiine therapy.

Anti-histaiiiine drugs ol' tlie H ,-receptor Ihckitig type are not consistently efltctive in the relief' of' those skin conditioiis wlirre

Mediulors of ullergic skin reaclion.~ in the horse 47

Iiistaniine is involved as an iniportant mediator. Hutchcroft r/ (11. (1979) f0iitid that intraclermal histamine effects in m o t 1 keys were markedly inhibited by H I-receptor anta- gonists but not by Hz-receptor blockers, while the combination of both receptor antagonists gave greater inhibition than that seen with H I-receptor blockade alone. Black PI cil. (1972) have shown that bloocl vessels in the cat antl the dog have HI arid Hz receptors. The wealing response of human skin to intla- dermal histamine also seems to involve HI and Hn receptors (Black P / d., 1972: Marks 8c " . . .leaves, 1977).

The value o f anti-histamines in the treat- ment of sweet itch or similar conditions in horses reported from other parts of the world is not certain. Frost (1974) reported that anti-histamines have been of little value in tlie treatment of sweet itch. However, McMullan (1'377) claimed that they are effective in relieving the priiritus associated with allergic dermatitis of' the horse, and Riek (1953) reported that the application of anti- histamine-containing creams was beneficial in allaying the irritation of Queensland itch, but frequent and extensive applications were necessary. The benefit of' tlie anti-histamine creams may have been, in part, due to meclianical interference with the feeding of midges. Pascoe ( 1973) found that I c ~ a l and parental anti-histamine therapy was successful in the treatment of Queensland itch. Naka- mui-a u/ (11. (1957, 1958) reported that sonie benefit was obtained from the use of anti- histamines in the treatment of Kasen disease, I x i t tlie ef'ftct was rather short-lived. Anti- histamine therapy, however, is of' little or no use in the treatment o f heaves (Brion u/ d., 1948). 'I'he anti-histaniine tlriigs used in this study have other pharmacologic~il actions, inclutling ~uiti-serotoiiergic activity in pro- methazine hydrochloride. While both driigs were effective in reducing the reactions pro- ducetl by tlie insect extracts, tlie mediation of hypersensitivity skin reactions i n tlie horse prolxi1)ly involves tlie interaction of' several diff'eretit niediators, antl tlie occurrence of allergic skin reactions coultl not be related to iiic.twsetl sensitivity to histamine, serotonin or br;itlyliinin.

ACKNOWLEDGMENTS

This study was supported by a grant from the Wellcome Trust. We wish t o thank Mrs Sheila O'Hanlon for her technical assistance.

REFERENCES

48 A. Morrow, P . J , Qiiiiirr & K. P . H(ikrt

tions to histamine and compound 48/80 in human skin; suppression by histamine H2-receptor blocking agent. British Journal of Clinical Pharma-

McMullaii, W.C. (1977) Equiiie clerinatology. Pto- crrdiiip of /he 22iicl A i i i i i i d ( . ‘ i i i i i w / i i i i i I!/ / / i r Aiiirrietoi Aa.\ucict/ioii I!/’ Eguiirr PJ~ic/i/ioiiri:c. Ed. Milrie, F..]., pp. 29:C:Mi.

Nakainura. K.. Matsuhashi. A. 8c Sakatii, K. (1!157) Stutlies 0 1 1 ‘kasen’ of horses i n Hokkaitlo. V. l’reliniinary experinieiits concerning the eflect o f anti-allergic drugs applied t o horses ;ifferred wi th the disease. J~piiit~t Joii r i i d i!f Vdi~ii i t i t y Ne\cw IT./I,

5. 97-1 I I. Nakamura, R., Kaneda, H., Kagota, K., Too, K.,

Sonoda, M., Ito, T., Inukai, Y., Sawada, M., Nakagawara, Y., Owada, K., Katagiri, Y. & Uetake, H. (1958) Studies on ‘Kasen’ of horses in Hokkaido. VI. Therapeutic significance of anti- histamine preparations for horses affected with

COIQQ, 4, 367-369.

the disease: Jabnese Jounml of Vrleritmry Research, 6. 123-133.

Neter. 1. 8c W;isseriiiaii, w. ( 1974) A/+/ii,i/ Liiirvir s /~ i /~s / i r r i / M f d r b , I st eclii. pp. 60.%;09. Irwin, tiomewcwd, Illinois.

ObeI. N.,]. (le Schmitei-liiw, (;.(;. (1!)4X) The action o f histaniine and other drugs o n the broiichial tolie in horses suffering from alveolar emphysenia (Heaves). Ae/n Pliciriiirieii/iigie~i r/ ?bxico/iigicri. 4. 7 I-xo.

l’ascoe. K.K. ( 1075) The natiire iind 1re;itnieiit o f skin coiiditioiis observed in horses i n Queens- I;~ntl. A i i . \ / tdioi i Vi,/wiiiois J o i i t i i d , 49, 3!WO.

(Luinri, P..].. Bitker, K.P. 8c Morrow, A.N. ( I< )XS) Sweet itch: responses o f cliriic;illy norni;il i ind at‘fectetl horses to iiitrxleniial cli;illenge with extracts of biting insects. Ei/iriirr V i ~ / r t i i i r r i ~ , / o i i i ~ i i ~ i / ,

15 (3). 2W4272. Kiek. K.F. (1!153) Stticlies o i i allergic tleriii;ititis o f