The effects of sexual experience and estrus on male-seeking motivated behavior in the female rat

Abstract

Ovariectomized (OVX) female rats were trained to traverse a straight alley and return to a goal box where they had previously encountered a male rat, a female rat or an empty goal box. The time required to run the alley was used as an index of the subjects' motivation to re-engage the goal box target. Subjects were tested in both estrus and non-estrus, first sexually naïve and then again after sexual experience. Female rats ran most quickly for a male target, most slowly for an empty goal box, and at intermediate speeds for a female target. Sexual experience tended to slow run times for all but male targets. Estrus enhanced approach behavior for males and an empty goal box, but tended to slow the approach toward females, both before and after sexual experience. This latter finding was further investigated in a second experiment in which sexually naïve OVX females were tested during estrus and non-estrus in a locomotor activity apparatus, a runway with an empty goal box, and an open field. Estrus produced no changes in spontaneous locomotion either in the activity box or the open field, but decreased run times in the alley and increased the number of center-square entries in the open-field. Thus, estrus produces increases in sexual motivation that selectively enhance exploratory, presumably male-seeking behavior, but not simple spontaneous locomotion. Keywords sexual motivation; runway; female rats; sexual experience; copulation; estrus; progesterone; estrogen A great deal is known about the sexual behavior of the female rat. For instance, in his seminal work on estrous females, Beach [1] outlined and illustrated a distinction between appetitive and consummatory behaviors, or proceptivity and receptivity, respectively. Receptivity is most closely understood as those behaviors "… which are necessary and sufficient for fertile copulation with a potent male" [1]. Receptive behaviors are those that facilitate the act of copulation, female rats, for example, exhibit displays of lordosis characterized by a crouching, sway-backed posture, with the tail flicked to the side to facilitate the male mounting and intromitting. It is well known that sexual receptivity in the female rat is dependent on the presence of estrogen [e.g, see 2,3,4]. Proceptivity, on the other hand, represents an antecedent condition to the copulatory act. Here the female exhibits solicitation activity that is intended to attract and stimulate the male [1]. In rats, such proceptive behaviors include hopping and darting, ear wiggles, and other orientCorresponding Author: Aaron Ettenberg, Ph.D., Department of Psychology, University of California, Santa Barbara, Santa Barbara, Voice: 805.893.3682, Fax: 805.893.4303, Email: ettenberg@psych.ucsb In previous work we assessed the motivation of male rats to traverse a straight-alley and enter a goal box where several seconds earlier they had been exposed to one of a variety of target stimuli placed on the opposite side of a Plexiglas partition. Although researchers have long used the runway as a mean...

Excitotoxic lesions of the nucleus paragigantocellularis facilitate male sexual behavior but attenuate female sexual behavior in rats

“…In particular, nPGi-lesioned animals did not increase the number of mounts received, or increase the amount of time spent in the mating arena, as is typically observed in females following successive mating experiences (Nofrey et al, 2008). Similarly, ejaculation-return latencies were significantly longer in nPGi-lesioned animals.…”

Adolescent cannabinoid exposure attenuates adult female sexual motivation but does not alter adulthood CB1R expression or estrous cyclicity

“…For instance, in control subjects we would expect females to express significantly lower RT’s for a male target when in estrus compared to when not in estrus. Indeed, such a difference has previously been observed in ovariectomized females given exogenous hormone treatment to induce behavioral estrus (Nofrey et al, 2008). We did see the expected pattern in our results, whereby subjects expressed lower RT’s and higher PT’s for a male target when estrous vs .…”

“…This apparatus has been previously utilized to assess socio-sexual motivation in both male (López and Ettenberg, 2000, 2001, 2002; López et al, 1999) and female rats (López et al, 2007, 2009, 2010; Nofrey et al, 2008). …”

The effects of medial prefrontal cortex infusions of cocaine in a runway model of drug self-administration: Evidence of reinforcing but not anxiogenic actions

“…Rats provided the opportunity to traverse an alley and enter a goal box for the delivery of bilateral mPFC infusions of cocaine, exhibited faster running over trials in much the same way that animals do when running an alley for natural reinforcers (e.g., Beach and Jordan, 1956; Ettenberg and Camp, 1986; Ettenberg and Horvitz, 1990; Lopez et al, 1999; Nofrey et al, 2008). These results therefore compliment and extend the findings of previous investigators who have reported that rats will readily learn to lever-press for self-administration of cocaine directly into the mPFC (e.g., Goeders and Smith, 1983, 1984; 1993; Goeders et al, 1986; McBride et al, 1999; see review by Tzschentke, 2000).…”