Participación del trabajo: DIFFERENTIAL stress response in Sprague Dawley (SD), Wistar (W) and OFA hr/hr (O) female rats. Effects of Diazepam.

GONZÁLEZ JATUFF A; RODRIGUEZ ECHANDÍA EL; VALDEZ, SUSANA R; JAHN GA

Göttingen, Alemania

Congreso; Seventh Göttingen Meeting of the German Neuroscience Society; 2007

German Neuroscience Society,

OFA hr/hr (O) rats are spontaneosly hairless and hipoprolactinemic with severe lactation deficit. Though prolactin (PRL) levels ares low, this hormone exhibits a higher increase after ether stress than other strain. Sensitivity to stress depends upon genetic and enviroment factors. In the present work we studied the behavioral stress response of female rats of three strains (O, SD and W) on oestrus day using two test: a) 1 min. exposure to a white noise, recording motor and exploratory activity before, during and after stressor application. b) restraint stress followed by plus-maze to evaluated the ansiogenic component. In the last test only W and O were observed. Diazepam (3mg/kg/day) was administered in the drinking water to randomly chosen animals, three days prior to plus-maze testing. Basal animals were given tap water. c) in a separated experiment hypothalamic tyrosine hydroxylase expression and DA and DOPAC levels were determined in lactating rats. Results: a) W and SD showed similar activity score and O was hyperactivity. Freezing response was exaggerated in W, while O showed the lowest score. W and SD pre-stress head-dipping scores fell to near 0 after stress; O exhibited a low score all the time. b) In the closed-arm, immobility basal scores were higher in O, but restraint stress lowered immobility. Basal and post-stress rearing were lower in O. Performance in the open arm was similar in W and O. Diazepam improved the plus-maze performance of basal O animals, but was unable to attenuate the effects of restraint-stress. c) TH expression and DA and DOPAC levels were increased in hypothalamus from pregnant and lactating O rats compared with the other strains. Conclusion: In O basal hole exploration is almost blocked, while novel object exploration is similar to the ether strain. Stress response was lower in the O group, while W rats showed the highest sensitivity to noise stress. The opposite effects in immobility scores of O in each testing condition may be due to motivational contextual cues. No differences in ansiogenic components were found. Results concerning TH, DA and DOPAC are consistent with previous work in other physiological situations. Dopaminergic systems are involved in most of the behavioral features observed in the present tetst. It is also known that PRL interacts with GABA system. Low circulating PRL and hyperfunctioning DA system could then be the bases of the differrences seen in the O group.