Repeated Paced Mating Increases the Survival of New Neurons in the Accessory Olfactory Bulb

You can read this on your own and ask your doctor if this is transferable to humans and to other areas than the olfactory bulb.  I'm being good by not commenting on this. 

Repeated Paced Mating Increases the Survival of New Neurons in the Accessory Olfactory Bulb

Wendy Portillo¹, Georgina Ortiz¹ and Raúl G. Paredes^1,2*

• ¹Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
• ²Escuela Nacional de Estudios Superiores, Unidad Juriquilla Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico

In female rats, the first sexual experience under paced mating conditions increases the number of newborn cells that migrate into the granular layer of the accessory olfactory bulb (AOB). Repeated paced mating has a potentiating effect on the number of new neurons that migrate to the AOB compared with a single session 15 days after paced mating. On the other hand, one paced mating session does no increases the survival of new cells 45 days after mating. In the present study, we evaluated if four paced mating sessions could increase the survival of new neurons in the AOB and main olfactory bulb (MOB) 45 days after females mated. Sexually naive female rats were ovariectomized, hormonally supplemented and randomly assigned to one of five groups: (1) Control, no sexual contact (C); (2) Four sessions in which females were exposed, without mating, to a sexually experience male rat (SE); (3) One session of paced mating (PM1); (4) Four sessions of paced mating (PM4); and (5) Four sessions of non-paced mating (NPM4). In the first behavioral test, females received the DNA synthesis marker 5-bromo-2′deoxyuridine and were euthanized 45 days later. Our data showed that the number of new cells that survived in the mitral cell layer of the AOB decreased when females were exposed to a sexually active male, in comparison to females that mated once pacing the sexual interaction. Repeated sexual behavior in pacing conditions did not increase the survival of new cells in other layers of the MOB and AOB. However, a significant increase in the percentage of new neurons in the granular and glomerular layers of the AOB and granular layer of the MOB was observed in females that mated in four sessions pacing the sexual interaction. In the group that paced the sexual interaction for one session, a significant increase in the percentage of neurons was observed in the glomerular layer of the AOB. Our data suggest that repeated paced mating increases the percentage of new neurons that survive in the olfactory bulb of female rats.

Introduction

Mating is a rewarding behavior that induces physiological and plastic changes. Female rats in natural, semi-natural and laboratory conditions can pace the sexual interaction, controlling the frequency and intensity of the sexual stimulation they receive (McClintock and Adler, 1978; Erskine, 1989). Mating in pacing conditions induces a reward state evaluated by the conditional place preference (CPP) test in male and female rats, mice and voles (Agmo and Berenfeld, 1990; Martinez and Paredes, 2001; Kudwa et al., 2005; Coria-Avila et al., 2006, 2008; Parada et al., 2012; Pfaus et al., 2012; Ulloa et al., 2018). When females or males mate without pacing the sexual interaction, this behavior does not induces a reward state (Martinez and Paredes, 2001; Ulloa et al., 2018).

Paced mating also induces plastic changes in the central nervous system. Adult neurogenesis is one of the most studied plastic changes. This process has been linked to reproduction from the early descriptions of its occurrence in adult life. Olfactory bulb (OB) neurogenesis in adult rodents is divided into three stages: proliferation, migration and survival. During proliferation (2 days) the stem cells replicate in the subventricular zone (SVZ) and rostral migratory stream (RMS). The new cells migrate (15 days) through the RMS and reach the glomerular (Gl), mitral (Mi), and granular (Gr) layers of the main and accessory olfactory bulb (MOB and AOB, respectively). The new cells that survive and integrate (45 days) into the OB layers become functional (Petreanu and Alvarez-Buylla, 2002; Winner et al., 2002). These stages are modulated by several internal and external factors. Thus, half of the new cells will die between 16 and 45 days after birth if they do not receive appropriate stimulation (Petreanu and Alvarez-Buylla, 2002; Winner et al., 2002).

The modulation of neurogenesis in the olfactory system in the adult brain in response to social and reproductive stimuli is well established (Peretto and Paredes, 2014; Bedos et al., 2018; Portillo et al., 2018). The first sexual experience in paced and non-paced conditions in female rats increases the proliferation of new cells in the RMS but does not increase the percentage of immature neurons (Corona et al., 2016). Paced mating increases the number of new cells that migrate to the Gr layer of the AOB but does not modify the number of new cells that survive in the MOB or AOB (Corona et al., 2011, 2016; Alvarado-Martinez and Paredes, 2018). However, the first paced mating experience increases the percentage of new cells that survive and differentiate into mature neurons in the Gr layer of the AOB (Corona et al., 2016). Constant sexual activity potentiates neurogenesis. Female rats that mate once a week for 4 weeks, pacing the sexual interaction, show an increase in the number of new cells and new mature neurons in the Gr layer of the AOB and MOB (16 days after their first sexual encounter) in comparison to females that mate four times under non-pacing conditions and females that mate once under pacing conditions (Arzate et al., 2013). Thus, repeated paced mating promotes the arrival of more cells that differentiate into mature neurons in the OB. In the present study, we evaluated if four sexual behavior tests before the critical time for cell survival (16 days) increases the number of new cells and neurons that integrate into the OB in female rats 45 days later.