Disruption of urinary odor preference and lordosis behavior in female mice given lesions of the medial amygdala

Abstract

Previous research showed that axonal inputs to both anterior and posterior subdivisions of the medial amygdala from the main and accessory olfactory bulbs of female mice, respectively, process volatile and non-volatile pheromonal signals from male conspecifics. In the present study we found that bilateral electrolytic lesions that included posterior portions, but not the anterior subdivision alone of the medial amygdala (Me) blocked the preference of estrous female mice to investigate volatile urinary odors from testes-intact vs. castrated males. Similar results were obtained in separate tests in which nasal contact with urinary stimuli was permitted. In addition, total time investigating volatile urinary stimuli was reduced in subjects with posterior Me lesions. Subjects were able to discriminate volatile urinary odors from testes-intact vs. castrated male mice, suggesting that this disruption of odor preference did not result from the inability of females given amygdaloid lesions to discriminate these male urinary odors. Bilateral lesions of the Me that were either restricted to the anterior or posterior subdivisions, or included areas of both regions, caused significant reductions in the display of lordosis behavior in estrous female mice. Our results suggest that the Me is a critical segment of the olfactory circuit that controls both mate recognition and mating behavior in the female mouse.

From sexual attraction to maternal aggression: When pheromones change their behavioural significance

“…Adult females prefer male-to female-derived chemosignals whether presented as an entire anaesthetised animal, a drop of urine or soiled-bedding. Similarly, adult females also prefer intact to castrated male-derived odours (Martinez-Ricos et al, 2007;DiBenedictis et al, 2012).…”

6-Hydroxydopamine lesions of the anteromedial ventral striatum impair opposite-sex urinary odor preference in female mice

“…These salient chemosignals (often referred to as pheromones) are detected by the main (MOS) and accessory olfactory systems (AOS) and relayed to the medial amygdala (Me). The Me is critical for odor-guided courtship and reproductive behaviors in female rodents [2–4]. It sends axonal projections to several downstream targets including the bed nucleus of the stria terminalis (BNST), the medial preoptic area (MPA), ventromedial (VMHvm), and ventrolateral (VMHvl) divisions of the ventromedial hypothalamus, and to numerous ventral striatal targets, including the nucleus accumbens core (AcbC) and shell (AcbSh), ventral pallidum (VP), medial olfactory tubercle (mOT) and islands of Calleja (ICj) [5–7].…”

“…Two days later, subjects were brought into estrus with an injection of progesterone (500μg, s.c.). Four hr after injection subjects were given a 5-min odor preference test in their homecage in which testes-intact male and estrous female urinary volatile odors were presented simultaneously (see [2] for details). This procedure was repeated 4 days later with the location of urinary cues reversed, and direct nasal access to the urinary stimuli permitted.…”

“…This procedure was repeated 4 days later with the location of urinary cues reversed, and direct nasal access to the urinary stimuli permitted. Two days following this test, subjects underwent a homecage habituation/dishabituation test to verify that subjects could discriminate between testes-intact male- and estrous female urinary volatiles [2]. Twenty-four hours later, animals were given a 48hr sucrose preference test [17] to determine whether ventral striatal DA depletion caused hedonic deficits leading to a decrement in sucrose consumption [18,19].…”

Neurobiology of social attachments

“…MeA and mPOA regulate the recognition and attraction toward sexually available partners, but also regulate sexual performance, integration of reward and neuroendocrine cascades that follow sex. In the case of social encounters the MeA is more responsive with non-volatile odors (normally present in bedding soiled with the excreta of estrous females, or partners), whereas mPOA (and CoA) respond more with volatile odors (from physically inaccessible partners) (Dhungel et al, 2011;DiBenedictis et al, 2012) (Fig. 1).…”