اکسی توسین در منطقه پری اپتیک داخلی رفتار جنسی نر در موش صحرایی را تسهیل می کند

Oxytocin (OT) belongs to a highly conserved family of peptides that regulate social and reproductive behaviors in vertebrates (Boyd - 1997 and Mahlmann et al - - 1994) - OT promotes female rat sexual and maternal behaviors (Caldwell et al - - 1989 - Caldwell et al - - 1994 - Pedersen et al - - 1982 and Pedersen et al - - 1994) and regulates male reproductive function - OT neurons in the male rat paraventricular nucleus of the hypothalamus (PVN) are activated (i - e - - Fos-immunoreactive - -ir) following copulation (Witt and Insel - 1994) or ex copula non-contact erections ( Baskerville et al - - 2009) - Infusion of nanogram (ng) amounts of OT into the lateral ventricles stimulates copulation in male rats ( Argiolas and Gessa - 1991 and Arletti et al - - 1985) - these effects are blocked by pretreatment with an OT receptor (OTR) antagonist (OTA) ( Arletti et al - - 1992) - Intracerebroventricular (icv) administration of an OTA increases intromission and ejaculation latencies and decreases mounts and intromissions ( Argiolas et al - - 1988) - In addition - OT binding sites and varicosities have been identified in thoracolumbar and lumbosacral spinal segments that control penile erection in rats - and OTR is expressed in penile tissue in men ( Veronneau-Longueville et al - - 1999 and Vignozzi et al - - 2004) - OT treatment (icv) induces ex copula penile erection in male rats ( Argiolas et al - - 1985) - these effects are dependent - in part - on stimulation of OTRs in the PVN and CA1 region of the hippocampus ( Melis et al - - 1986) - Male rats that fail to copulate to ejaculation have lower levels of OT mRNA in the PVN - compared to sexually vigorous males ( Arletti et al - - 1997) - OT can also restore copulation in males whose copulatory behavior had been impaired by chronic fluoxetine ( Cantor et al - - 1999) - Plasma concentrations of OT increase during the sexual response in rats and humans ( Carmichael et al - - 1987 and Stoneham et al - - 1985) - and a link between sexual impotence and reduced central OT production has been established in the male rat ( Arletti et al - - 1997) - OT and the mesolimbic dopamine system interact to promote male rat sexual behavior - Microinjection of OT into the PVN - ventral tegmental area (VTA) - ventral subiculum - or posteromedial cortical nucleus of the amygdala induces penile erection and increases dopamine levels in the nucleus accumbens (NAcc) (Melis et al - - 2007 - Melis et al - - 2009 - Succu et al - - 2007 and Succu et al - - 2008) - OTA treatment (icv) reduces non-contact erections in the presence of a receptive female (Melis et al - - 1999) - and intraperitoneal (ip) injections of OT stimulate the onset of copulation in aging (20-month old) male rats (Arletti et al - - 1990 and Arletti et al - - 1992) - Taken together - the available data suggest that OT is involved in both the consummatory and appetitive phases of the sexual response in males - Most pharmacological studies of the effects of OT on male sexual behavior have used icv administration of OT or OTA - the relatively few researchers who tested site-specific effects focused primarily on the PVN - VTA - hippocampus - and amygdala - Less attention has been given to the medial preoptic area (MPOA) - a major site of integration for male sexual behavior (reviewed in Hull et al - - 2002 and Hull and Rodriguez-Manzo - 2009) - OT-producing neurons and OT binding sites have been identified in the MPOA of male rats (Tribollet et al - - 1992) - and OT-containing MPOA neurons are activated (Fos-ir) by copulation (Baskerville et al - - 2009) - In female rats - a few OT-ir neurons in the MPOA project indirectly to the clitoris and vagina - suggesting a role for OT in the MPOA in the control of sexual function in females (Gelez et al - - 2010) - Thus - a major goal of the present study is to determine whether OT acts in the MPOA to facilitate male sexual behavior - There is a great deal of variability in reproductive behavior of rodents - In female rats - levels of OTR binding are higher in high licking and grooming (LG) mothers than in low LG mothers (Francis et al - - 2000) - In addition - more maternally responsive females have higher levels of OTR binding in the amygdala - bed nucleus of the stria terminalis - and MPOA compared to mothers that are less responsive (Champagne et al - - 2001) - We wished to test whether differences in OT or OTR activity in the MPOA may be associated with differences in male sexual behavior - Using factor analysis - Sachs (1978) condensed 10 measures of copulatory behavior into 4 factors - An initiation factor comprises latencies to the first mount and intromission - Intromission count factor corresponds to the number of intromissions required to elicit an ejaculation - Hit rate factor is the ratio of successful penile intromissions to total mount attempts - Copulatory rate factor includes the latency to the first ejaculation - latency to the resumption of copulation following an ejaculation - and average time interval between intromissions - Efficiency generally refers to the ability to accomplish a goal effectively - with minimal waste of time or resources - Therefore - we hypothesized that intra-MPOA injection of OT would improve sexual efficiency by facilitating one or more of the above factors—i - e - - increase hit rate factor and decrease initiation - copulatory rate - and intromission count factors - whereas injection of an OTA was expected to inhibit one or more of these factors - We also hypothesized that sexual efficiency would be correlated with OTR binding in the MPOA of sexually experienced male rats -