A preliminary study of the efficacy of fluphenazine as a treatment for fescue toxicosis in gravid pony mares

Induced lactation with a dopamine antagonist in mares: different responses between ovariectomized and intact mares

The aim of this study was to compare the effects of treatment with repeated injections of sulpiride (a dopamine D2 antagonist) on prolactin secretion and induced lactation in ovariectomized and intact adult mares and to verify if this induction was possible at the beginning and at the end of the birth season. Two experiments were carried out in September [experiment (expt) 1], and in March (expt 2), in France (48 degrees N). In expt 1, three groups of five mares were tested: intact-control, intact-treated and ovariectomized-treated mares. In expt 2, mares previously subjected to artificial photoperiod were assigned in two groups: four intact-control and five intact-treated mares. The cyclicity of intact mares was previously synchronized with PGF2alpha injections, then all the mares were in the follicular phase at the beginning of treatment. Sulpiride was intramuscularly injected (0.5 mg/kg of BW), twice a day. Mares were milked at 7:30, 11:45, 16:00 and 20:15 hours. Blood samples were collected every day during the treatment for progesterone, total oestrogen and prolactin assays. In the two experiments, only treated intact mares produced milk, with a large inter-animal variability. Prolactin increase after sulpiride treatment was not so great in the ovariectomized-treated mares as in the intact-treated mares. The total correlations between prolactin, progesterone, oestrogen plasma concentrations and daily milk production were significant (0.57, 0.25, 0.17 respectively). This induction of lactation can be performed during the entire birth season in intact mares, but not in ovariectomized mares, indicating that steroids are necessary for this induction in mares treated by dopamine D2 antagonist.

Ergovaline toxicity on Caco-2 cells as assessed by MTT, alamarBlue, and DNA assays

The exact mechanisms of fescue toxicity in animals have yet to be established, but it has been associated with an inability to thrive. Ergovaline is the major ergopeptine alkaloid associated with fungal infections of tall fescue. Gastrointestinal (GI) toxicity of ergovaline (10(-11) to 10(-4) M) was evaluated in Caco-2 cells (mimicking the GI epithelium) beginning on days 1, 8, and 18 of culture. Acute and chronic toxicity was assessed after 24 and 72 h of exposure. Treatment periods were chosen to study undifferentiated, semidifferentiated, and completely differentiated cells. Cell loss and metabolic activity were assessed by thiazolyl blue reduction (3-(4,5-dimethylthiozole-2-yl)-2,5,-biphenyl tetrazolium bromide [MTT], mitochondrial succinate dehyrdogenase activity), alamarBlue assay (cytochrome oxidase activity), and deoxyribonucleic acid (DNA) quantitation. Undifferentiated cells were sensitive to 1 x 10(-4) M ergovaline after acute exposure (from 52 to 74% of control values depending on assay). After 72 h of exposure to 1 x 10(-4) M ergovaline, in all three assays, treatment means were reduced to approximately 10% of the control means. By day 11 in culture, ergovaline toxicity to cells had decreased. With 24 h exposure, an apparent paradoxical increase in MTT was seen at some concentrations. This increase in MTT was also found in fully differentiated cells (day 21), whereas alamarBlue activity decreased. No change in DNA was found until 72 h of exposure, when DNA was reduced approximately 12% over most concentrations. These findings indicate differentiation state-dependent sensitivity of Caco-2 cells to ergovaline, potential problems of the MTT assay as an indicator of cellular toxicity, and usefulness of alamarBlue assay over DNA assay for toxicity assessment.

Systemic relaxin in pregnant pony mares grazed on endophyte-infected fescue: effects of fluphenazine treatment

Tall fescue is one of the most widely grown forage grasses for horses in the United States. However, it is frequently infected with the endophyte Neotyphodium coenophialum which produces ergot alkaloids that cause severe adverse effects in the pregnant mare. The objectives of this study were to determine the effects of fescue toxicosis and fluphenazine on circulating relaxin in pregnant pony mares and evaluate the usefulness of relaxin as a monitor of treatment efficacy. Twelve mares were maintained on endophyte-infected tall fescue pasture. Group TRT (n = 6), received 25 mg of fluphenazine decanoate (i.m.) on Day 320 of gestation while Group UTRT served as untreated controls. Daily blood samples were collected from Day 300 of gestation until Day 3 post partum and analyzed for plasma relaxin concentrations using a homologous equine radioimmunoassay. Mean gestation lengths were 330 +/- 0.7 and 336.5 +/- 3.2 days for TRT and UTRT mares, respectively (P = 0.07). Mean plasma relaxin concentrations in both groups of mares during the week before treatment (Day 313 to 319) were not different (UTRT, 53.4 +/- 11.3 ng/mL; TRT, 61.4 +/- 9.3 ng/mL). In the week after treatment (Day 320 to 326), mean plasma relaxin tended to be higher (P = 0.1) in TRT mares (66.7 +/- 6.2 ng/mL) when compared with UTRT mares (49.6 +/- 6.6 ng/mL), representing a 17.1 ng/mL difference in circulating relaxin between the two groups. Systemic relaxin during the last week before delivery (days relative to parturition) for UTRT and TRT mares was 45.7 +/- 6.7 and 64.7 +/- 6.4 ng/mL (P = 0.06), respectively. At Day -8 and Day -5 relative to parturition, systemic relaxin in TRT mares was significantly higher (P < 0.05) than in UTRT mares. Three of the six UTRT mares and one TRT mare showed clinical symptoms of fescue toxicosis. In the week before delivery, circulating relaxin in mares with problematic pregnancies (39.9 +/- 7.8 ng/mL) was significantly lower than concentrations measured in mares with normal pregnancies (63.4 +/- 5.4 ng/mL; P = 0.03). Clinical observations suggest that a one-time injection with fluphenazine improved pregnancy outcome by reducing the adverse effects of fescue toxicosis concomitant with a stabilization of plasma relaxin concentrations. These data support the hypothesis that systemic relaxin may be a useful biochemical means of monitoring placental function and treatment efficacy in the mare.