Date of this Version
The develop~llenot f nonsurgical co~ltraceptivesf or cats may facilitate population control of the species. The purpose of this study was to investigate the utility of GI&H for iinillu~locontraceptioo~fl male cats. Male cats (11=12) were divided into groups of tlxee and were inunuilized once with 0 (sham), 50, 200, or 400 i g synthetic GI&H coupled to keyhole limpet hernocyanin and combined with a nlycobacterial adjuvant to e~lhance inullunogenicity. GI&H ailtibody titer, serunl testostero~lec oncentration, and scrota1 size were detenniiled monthly. At 6 1110, semen was collected by electroejaculation and testes were examined histologically. GnRH antibodies were detected in all cats receiving GuRH vaccine by 1 nlo post-treatment and persisted tl~oughouth e study. No dose effect of GnRH was observed as titers were not significantly different between cats treated with 50, 200, or 400 i g GnRH (P = 0.5). Six of ni11e treated cats were classified as responders based on high GIIRH ailtibody titers (>32,000). By 3 mo post-treat~llent,r espo~lderc ats had undetectable testosteroile and testicular atrophy. Nonrespoilder cats had GnRH titers of 4,000 to 32,000 and testosterone conce~ltrationsin tei-nlediate between responder and sllailr treated cats. At 6 mo, total spenn counts were similar for shamtreated cats (3.1 i 1 S x lo6 sperm) and noixesponder cats (3.4 k 1.6 x lo6 sperm; P = 0.7). Only one of the six responder cats produced spei-111, none of which were motile. Co~llbinedte sticular weights of respoilder cats (1.3 k 0.1 g) were lower than sha~n-treatedc oiltrols (5.3 * 1.3 g; P = 0.02) and ilomesponder cats (2.9 k 0.3 g; P = 0.02). Histologic evaluatioil of the testes revealed that in responder cats, the interstitial cells that were present were pale and shruilltei~c onlpared to the pluillp, polyhedral eosinophilic cells in shan~treatedc ats. GnRH responder cats had marked tubular atrophy with vacuolated Sertoli cells and a paucity of germ cells. SingIe-dose GnRH treatment resulted in testosterone concelltrations and semen quality coilsistent with imrnunocastration in a majority of cats treated.