6-Hydroxydopamine lesions enhance progesterone-facilitated lordosis of rats and hamsters, independent of effects on motor behavior

Abstract

The Ventral Tegmental Area (VTA) is an important brain area for progesterone (P4)'s effects to facilitate female sexual behavior of rodents. We investigated the importance of dopaminergic neurons in the VTA, and two dopaminergic projection sites, the Nucleus Accumbens (NAc), and Caudate Nucleus of the Striatum (CN), in modulating P4-facilitated sex and motor behavior. Ovariectomized (ovx) rats and hamsters, administered estradiol benzoate (10 μg) and P4 (0, 50, 100, 200, or 500 μg), were tested for motor behavior in a chamber that automatically records horizontal beam breaks, and for sexual behavior in response to a sexually-experienced male. Animals were tested once a week until each P4 dosage was received; animals then had bilateral 6-hydroxydopamine (6-OHDA) or sham lesions to the VTA, NAc, or CN and were re-tested at each P4 dosage on subsequent weeks. Fixed brains were stained with cresyl violet and processed for dopamine transporter (DAT) immunoreactivity. The number of cresyl violet stained cells was significantly lower in all 6-OHDA infusion sites compared to non-6-OHDA infusion sites of rats and hamsters. Also, in rats, the number of DAT-immunoreactive neurons was lower in all 6-OHDA infusion sites compared to non-6-OHDA infusion sites. In rats, 6-OHDA but not sham, lesions to the VTA, NAc, or CN produced P4-dependent increases in lordosis quotients and resulted in modest increases in motor behavior. In hamsters, 6-OHDA, but not sham, lesions to the VTA, NAc, or CN produced P4-dependent increases in total lordosis durations and produced modest decreases in motor behavior. This suggests that the dopaminergic output neurons of midbrain VTA may play an important role in modulation of P4-facilitated sexual lordosis among rodents.

Behavioral indices of breeding readiness in female European starlings correlate with immunolabeling for catecholamine markers in brain areas involved in sexual motivation

“…A significant, positive correlation identified between nesting behavior and the density of TH (but not DBH) immunolabeling in Ac in spring-like females also links dopamine activity in Ac to female breedingreadiness. These findings are consistent with a well-established role for dopamine in Ac in rodents in multiple, highly motivated, reward-directed behaviors, including sexually-motivated female behaviors (as reviewed in the introduction [18,19,28,29,39,45]. The present results in songbirds are consistent with the possibility that dopamine in the Ac may also contribute to individual differences in female breeding readiness.…”

“…For example, norepinephrine release in the ventromedial nucleus of the hypothalamus (VMH) facilitates lordosis responses in female rats [16,32,33,44]. Dopamine in the ventral tegmental area (VTA; the source of dopaminergic projections to the striatum, including the nucleus accumbens (Ac)) also facilitates lordosis [18,19], and dopamine release in the Ac occurs during sexually-motivated, proceptive female behavior directed towards males [28,29,39,45]. In female rodents, dopamine activity in the medial preoptic nucleus (referred to as POM in birds) also influences female sexual behaviors in a complex receptor subtype-specific manner [20].…”

Progesterone prevents depression-like behavior in a model of Parkinson's disease induced by 6-hydroxydopamine in male rats

“…It is well known that progesteronewhen used in 6-OHDA injected subjectsaffects motor components as well as reproductive behaviors in female rats and hamsters (Hansen et al, 1991;Frye et al, 2010). Here we centered our interest around two common non-motor-nonreproductive-symptoms (Tadaiesky et al, 2008): 1) cognitive disorders in an appetitive model of memory (by using a novel object recognition test); and 2) depression-like behaviors (by using a forced swimming test).…”

Central Actions of 3α,5α-THP Involving NMDA and GABAA Receptors Regulate Affective and Sexual Behavior of Female Rats

“…The midbrain VTA consists of a mixture of dopaminergic (∼65%) and non-dopaminergic neurons, the latter of which are largely GABAergic (∼30%) or glutaminergic (∼5%; Zessen et al, 2012). Activation of dopaminergic efferents from the VTA to forebrain structures (particularly, within the striatum) are generally observed to inhibit lordosis and lesioning or quiescing these neurons facilitates lordosis (Caggiula et al, 1979;Sirinathsinghji et al, 1986;Pednekar and Mascarenhas, 1993;Frye et al, 2010). By virtue of 3α,5α-THP's potent affinity for GABA A receptors, it rapidly promotes Cl − influx into neurons, reducing excitability (Majewska et al, 1986;Lambert et al, 1987).…”