Biomedical subjects

D Mir

Publications and source records attributed to D Mir.

11 recordsLinked to original sources

PubMed1991

Accumbens lesion in female rats increases mount rejection without modifying lordosis.

Ovariectomized Wistar rats received bilateral electrolytic (n = 24) or sham (n = 11) lesion of the nucleus accumbens. Following priming with estradiol benzoate (25 micrograms/rat) and progesterone (0.5 mg/rat) they were tested for sexual behavior with a stud male. Tests were carried out once prior to operation and twice postoperatively. Both lordosis and rejection behaviors as responses to male mount attempts were evaluated for each session. Proceptive patterns (hopping, darting and presenting) were also recorded. Females with accumbens lesion did not differ from control animals either with regard to lordosis or to soliciting behaviors. On the contrary, the lesioned group showed a statistically significant increase in rejection behavior in both postoperative sessions (p less than 0.05 and p less than 0.002). In conclusion, nucleus accumbens lesion dissociated the normal correlation between lordosis and rejection responses to male mount attempts without affecting soliciting behaviors. This finding is thought to be related to the hyperreactivity produced by nucleus accumbens lesion.

Aggression↗

PubMed1990

Effects of nucleus accumbens lesion on female rat sexual receptivity and proceptivity in a partner preference paradigm.

A partner preference paradigm, stud male vs estrous female, was used to study sexual behavior. Ovariectomized Wistar rats received bilateral electrolytic (n = 33) or sham (n = 16) lesion of the nucleus accumbens. Animals were tested in two different experimental situations, either with stimulus animals tethered (test with possibility of mating) or with stimulus animals behind a wire mesh (test without possibility of mating). Each test was carried out once prior to surgery and twice postoperatively following priming with estradiol benzoate and progesterone. Lordosis, rejection behaviors and soliciting patterns were scored in tests with tethered stimulus animals. The tendency of the experimental female to approach and remain in the vicinity of each stimulus animal was quantified to study the partner preference. Nucleus accumbens lesion increased the number of rejection responses to male mount attempts without modifying either receptivity estimated by lordosis reflex or soliciting behaviors. Control females showed a statistically significant preference for the male throughout the experiments. Lesioned females exhibit a preference for the male only in the test without sexual interaction possibility. This preference disappeared in the test with possibility of mating and it was even reversed when the male showed copulatory activity. These results, together with the absence of changes in lordosis behavior and soliciting activity, suggest that both the inversion in preference and the higher levels of mount rejections found in the lesioned animals are more likely attributable to hyperreactivity to the copulatory stimulus rather than an alteration in the female's rat sexual motivation.

Animals↗

PubMed1990

Behavioral study in rats of paired accumbens-lesioned residents and intact intruders.

Behavior in accumbens-lesioned male Wistar rats during paired encounters was assessed by several parameters, scores and cluster analysis based on similarity between patterns. Encounters were videotaped and analyzed by an ethogram and a software package previously elaborated. Residents were lesioned (n = 23) or sham operated (n = 10). A reactivity score was used to corroborate the effectiveness of the lesions. Although accumbens lesions produced the well-known increase in reactivity and enhancement of piloerection, only subtle changes were elucidated by the ethological analysis. Dendrograms revealed postoperative changes in the lesioned rats as well as in the intruders paired with them. Threat category in the lesion group dissociated in threat with arched-back attitude and threat with erect posture. In intruders paired with lesioned rats, compared with those paired with sham-operated animals, the patterns of freezing and on-back became mainly associated with immobile-crouch instead of upright defense posture, and the category of defense/submission was not observed in dendrograms.

Aggression↗

PubMed1987

Effects of nucleus accumbens lesions in rats on spatial preference in an open field.

Selective lesions placed in three different regions of the nucleus accumbens were performed to assess their effects on spatial preference in the rat. Histological verification allowed to establish three groups of lesioned animals: medial, intermediate and lateral. Sham operations involved all procedures except the passing of a current. All animals were tested once prior to operation and twice postoperatively. Sherman's directionality score (DS) was adopted. Positive values indicate right side preference and negative ones leftward bias. Statistical analysis revealed that rats used in this study showed a nonsignificant spontaneous right side preference in the open field (DS = +0.08). Medial and intermediate lesions increased the right side bias (DS = +0.37), whereas lateral lesioned animals reversed their preoperative rightward bias and showed a significant left side preference (DS = -0.48). These results suggest a participation of the nucleus accumbens in spatial preference and are considered to be due to the well known uneven distribution of the afferent and efferent fiber systems within the nucleus.

Animals↗

PubMed1987