Resumen

MEDINA, Iraima  y  DALO, Nelson L. Ketamine decreases the level of luteinizing hormone in dairy cows. Zootecnia Trop. [online]. 2009, vol.27, n.3, pp.271-276. ISSN 0798-7269.

The hypothalamus integrates excitatory signals mediated by glutamate that result in the release of gonadotropin releasing hormone (GnRH) that regulates the adenohypophysis luteinizing hormone (LH) secretion, which has a pivotal role in reproductive cycle. This neuro endocrine action of glutamate is susceptible of being blocked by N-methyl-D-aspartate (NMDA) receptor antagonists, among others, ketamine. The main goal of this work was to determine whether a low dose of ketamine induces a decrease in the plasmatic level of LH in cows. Twelve Carora breed dairy cows, not pregnant and showing signs of estrous were used. Cows were divided in two groups. Six of them were injected with ketamine (1 mg/kg, IV), diluted in 20 mL of 0.85% saline solution and six were injected with the solvent. Blood samples were taken every 5 min and the LH levels were quantified by chemiluminescence. Ketamine produced 5 min after its injection a significant decrease in LH level that lasted 50 min. From 55 to 120 min, the LH levels returned to control values. This potent effect of ketamine on the LH let us suggest that similar situation may occur with others antagonistic substances that alter the glutamatergic system, may also disrupt the reproductive cycle.

Palabras clave : ketamine; luteinizing hormone; LH; GnRH.

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