Effects of Various Methods of Sulpiride Administration on Prolactin Release in Horses.

This research explores the effects of various methods of sulpiride administration on the release of prolactin in horses, showing that the duration of prolactin responses can be significantly extended by using hydrophobic vehicles like vegetable shortening or SucroMate.

Experiment 1: Comparison of Different Sulpiride Enantiomers

• The first experiment assessed the efficacy of the (-) enantiomer of sulpiride compared to the commonly used (+/-) racemic mixture.
• Mares were used in this study and compared for prolactin responses to four doses of levosulpiride and four corresponding doses of the racemic mixture at twice the dose.
• The results indicated that the responses at each dose were equal and similar, suggesting that either enantiomer could be used without significant difference in effect.

Experiment 2: Comparison of Oral vs. Injected Sulpiride

• Experiment two compared the efficacy of 1 gram of orally administered racemic sulpiride to 100 mg of intramuscularly injected sulpiride in oil in mares that were primed with 50 mg of estradiol cypionate (ECP).
• The prolactin response in groups receiving sulpiride was robust but similar in magnitude, with minor differences in timing.
• This indicates that the method of administration (oral vs. intramuscular) had little effect on the overall prolactin response.

Experiment 3: Effect of Injection Site on Prolactin Response

• Experiment three involved ECP-primed geldings that received subcutaneous injections of 1.8 grams racemic sulpiride in vegetable shortening in one of three sites: the neck, the back below the withers, or the lower girth region.
• Control geldings received no sulpiride.
• Prolactin responses to sulpiride lasted a minimum of 96 hours in all cases, indicating that the site of subcutaneous injection does not notably affect the duration of the prolactin response.

Experiment 4: Hydrophobic Vehicles and Prolactin Response

• The final experiment compared the prolactin responses to 3 grams of racemic sulpiride in vegetable shortening with similar injections in 5 mL of sucrose acetate isobutyrate (SAIB; SucroMate), or SAIB alone, in ECP-primed geldings.
• Controls had no prolactin response to SucroMate, whereas both treatment groups had extended prolactin responses lasting at least 10 days.
• The conclusion from this experiment is that the duration of prolactin responses to sulpiride in horses can be significantly extended by using hydrophobic vehicles like vegetable shortening or SAIB.