Lordosis facilitation by LHRH, PGE2 or db-cAMP requires activation of the kinase A signaling pathway in estrogen primed rats.

Dose-response curves for lordosis and proceptive behaviors were obtained for luteinizing hormone releasing hormone (LHRH), prostaglandin E2 (PGE2) and dibutyryl cyclic AMP (db-cAMP), by infusing them in the right lateral ventricle (i.c.v.) of ovariectomized (OVX) estradiol benzoate (E2B; 2 microg) treated rats. Two dose levels, one producing the maximal effect and the other one producing a submaximal response (approximately ED50) were selected for testing the capacity of Rp-cAMPS, a kinase A blocker, to modify the behavioral response to the three compounds. I.c.v. injections of Rp-cAMPS, significantly depressed both lordosis and proceptive responses induced by LHRH, PGE2 and db-cAMP. The results show that these agents use the cAMP-kinase A signaling pathway to elicit their stimulating effect on estrous behavior in the rat.

Differential effect of kinase A and C blockers on lordosis facilitation by progesterone and its metabolites in ovariectomized estrogen-primed rats.

Dose response curves for lordosis behavior was obtained for progesterone (P) and its two ring A-reduced metabolites: 5alpha-pregnanedione (alpha-DHP) and 5alpha,3alpha-pregnanolone (5alpha,3alpha-Pgl) by infusing these progestins in the right lateral ventricle (rlv) of ovariectomized (ovx) estradiol-treated rats (2 microg estradiol benzoate; EB), 40 h before intracerebro-ventricular (icv) injection. Effective doses 50 (ED50) revealed that ring A-reduced progestins were more potent than P itself to induce lordosis behavior. Two dose levels, one producing the maximal effect and the other one producing a submaximal response (ED50-ED60), were selected for testing the capacity of RpAMPS, a kinase A blocker, and H7, a kinase C blocker, to modify the response to the three progestins. rlv injection of RpAMPS significantly depressed the lordosis response to the two dose levels of P and alpha-DHP but failed to significantly inhibit that of 5alpha,3alpha-Pgl. The administration of H7 prevented the effect of both 5alpha-reduced progestins without affecting the response to P. The results suggest that P and its ring A-reduced metabolites stimulate lordosis behavior through different cellular mechanisms: P acting mainly through the cAMP-kinase system; alpha-DHP through both kinase A and kinase C signaling pathways and 5alpha,3alpha-Pgl through the kinase C system.

Progestins and place preference conditioning after paced mating.

When female rats pace their coital interaction, a reward state evaluated by conditioned place preference is induced. Progesterone (P) is essential for the expression of proceptive behavior and for the induction of CPP. However, the functional significance of ring A reduction of P for the induction of this state during estrous is unsettled. In the present study, we evaluated whether ring A-reduced metabolites of P are involved in the reward state induced when the females are allowed to pace their sexual contacts. Ovariectomized (ovx) female rats treated with estradiol benzoate (EB, 5 microg) and P (13 microg), Megestrol acetate (MA; 13 microg ), 5 alpha-pregnan-20 dione (5 alphaDHP; 3 microg), or 5 beta-pregnan-3 alpha-ol-20-one (5 beta,3 alpha-Pgl; 3 microg) were used. Progestins were dissolved in propylene glycol and intravenously (iv) injected through an indwelling jugular catheter before females were tested for pacing behavior. After 15 intromissions or one ejaculation, females were gently placed in the nonpreferred compartment of a CPP box. Paced mating in all groups treated with progestins induced a clear change of preference. The administration of progestins alone did not induce CPP. These results suggest that P and ring A-reduced metabolites facilitate the reward state following pacing.

Seasonal dynamics of ruminal crude protein digestion of browse species from Baja California Sur México

Diez arbustos nativos de Baja California Sur, México, fueron nutricionalmente evaluados en cada estación durante tres años consecutivos, midiendo proteína cruda (PC), fracción proteína en la fibra detergente neutro (FPDN) y en la fibra detergente ácido (FPDA), y velocidad y grado de degradabilidad de PC. Cinco leguminosas y cinco no-leguminosas fueron colectadas de 16 transectos lineales de 30m. Todos las plantas de cada transecto fueron identificadas y medidas para estimar el índice de diversidad Shannom, riqueza de las especies, cobertura aérea y frecuencia relativa, dominancia, densidad e importancia. Heno de Medicago sativa L. fue usado como forraje de referencia de alta calidad nutritiva. Para estimar la degradabilidad efectiva de PC (DEPC), se usaron por duplicado bolsas nylon (10x15cm; poro de 50 por ciento) conteniendo 4g cada especie de cada estación y año,incubadas en la parte ventral del rumen de cuatro becerros de carne canulados. En general, el contenido de PC, FPDN, FPDA y DEPC fueron significativamente mayores en leguminosas. La PC soluble en la fibra detergente neutro fue mayor en las no-leguminosas en primavera y verano, y PC y DEPC fueron mayores en otoño. La DEPC en leguminosas fue significativamente menor en verano, posiblemente por reducción en la proteína disponible de la pared celular. Solo especies como Opuntia cholla, Prosopis sp. y Cercidium floridium tuvieron valores de DEPC comparables o mayores a la alfafa. Cyrtocarpa edulis tuvo la menor DEPC. La PC de leguminosas fue más degradada en el rumen que las no-leguminosas. Se distinguen dos períodos de calidad nutritiva, uno de alta calidad en otoño e invierno y otro de baja en primavera y verano.