فعالیت عصبی ناشی از رابطه جنسی و پرخاشگری در سراسر جمعیت وازوتوسین در آنول قهوه ای

Activity within the social behavior neural network is modulated by the neuropeptide arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP). However, central AVT/AVP release causes different behavioral effects across species and social environments. These differences may be due to the activation of different neuronal AVT/AVP populations or to similar activity patterns causing different behavioral outputs. We examined neural activity (assessed as Fos induction) within AVT neurons in male brown anole lizards (Anolis sagrei) participating in aggressive or sexual encounters. Lizards possess simple amniote nervous systems, and their examination provides a comparative framework to complement avian and mammalian studies. In accordance with findings in other species, AVT neurons in the anole paraventricular nucleus (PVN) were activated during aggressive encounters; but unlike in other species, a positive correlation was found between aggression levels and activation. Activation of AVT neurons within the supraoptic nucleus (SON) occurred nonspecifically with participation in either aggressive or sexual encounters. Activation of AVT neurons in the preoptic area (POA) and bed nucleus of the stria terminalis (BNST) was associated with engagement in sexual behaviors. The above findings are congruent with neural activation patterns observed in other species, even when the behavioral outputs (i.e., aggression level) differed. However, aggressive encounters also increased activation of AVT neurons in the BNST, which is incongruous with findings in other species. Thus, some species differences involve the encoding of social stimuli as different neural activation patterns within the AVT/AVP network, whereas other behavioral differences arise downstream of this system.

Social behaviors are differentially regulated by varying activity levels across a social behavior neural network consisting of various brain regions and neural chemicals (Albers, 2012, Goodson, 2005, Goodson and Kabelik, 2009, Newman, 1999, O'Connell and Hofmann, 2011, O'Connell and Hofmann, 2012, Sakata et al., 2000 and Yang and Wilczynski, 2007). The neuropeptide arginine vasotocin (AVT), known in mammals as arginine vasopressin (AVP) due to a single amino acid substitution, is a neuromodulator known to regulate social behaviors across a wide variety of vertebrate taxa (Albers, 2012, De Vries and Panzica, 2006, Godwin and Thompson, 2012, Goodson, 2008, Goodson et al., 2012 and Moore, 1992). However, this neuropeptide's role in the regulation of social behaviors is unclear, likely due both to species differences in AVT/AVP distributions (Bester-Meredith et al., 1999, Dewan et al., 2011, Moore and Lowry, 1998 and O'Connell and Hofmann, 2012) and the propensity for different AVT/AVP populations to become activated under different experimental/social conditions (Goodson and Bass, 2001, Goodson and Kabelik, 2009, Goodson et al., 2009b, Kabelik et al., 2009 and Veenema et al., 2010). These different populations can then modulate different target sites and elicit different behavioral responses. For instance, Veenema et al. (2010) demonstrated that AVP release in the lateral septum of Male Wistar rats correlates positively with intermale aggression, whereas release in the BNST correlates negatively with such aggression. Furthermore, each AVT/AVP population may itself play multiple roles, with involvements in the regulation of multiple social behaviors and neuroendocrine functions (Caldwell et al., 2008, Goodson and Kabelik, 2009, Landgraf and Neumann, 2004 and Marler et al., 2003). Hence, it is important to examine distinct patterns of AVT/AVP activity across multiple nodes of its own network in order to better understand how this AVT/AVP network modulates activity in the greater social behavior neural network. We here examine behavioral induction of the immediate early gene (IEG) product Fos, a marker of neural activity (Herdegen and Leah, 1998 and Hoffman et al., 1993), within a number of neural AVT populations that are relatively conserved among tetrapod vertebrates and that have been shown to be relevant to the regulation of social behaviors (De Vries and Panzica, 2006, Goodson and Kabelik, 2009 and Moore and Lowry, 1998). We examine these AVT populations within the very small and simple brain of the brown anole lizard (Anolis sagrei). Reptilian brains are considered evolutionarily primitive and similar to ancestral mammals ( MacLean, 1978), and their examination can shed light on the evolution and functionality of more highly derived mammalian and avian circuitry. Even though lizards serve as excellent models of neural connectivity among nuclei in the social behavior neural network ( Sakata et al., 2000 and Yang and Wilczynski, 2007), few investigations of AVT within reptilian brains have been conducted and information about the involvement of AVT in the regulation of social behaviors is greatly lacking. That is, although reptilian studies exist demonstrating the effects of AVT on parturition and oviposition ( Figler et al., 1989, Guillette and Jones, 1980, Guillette and Jones, 1982, Jones and Guillette, 1982 and Propper et al., 1992a), we know of no studies demonstrating direct associations between AVT and the performance of aggressive or sexual behaviors. Hence, we here examine Fos induction (a measure of neural activity) within AVT neurons of male brown anoles following exposure to same-sex versus opposite sex individuals. Furthermore, we examine the individual variation within each of these social interaction treatment groups to determine associations between AVT activity and behavioral intensity, frequency, and latency to perform aggressive or sexual behaviors. Finally, we also compare the stimulus animals' behaviors with AVT-Fos colocalization rates within focal males' brains. The AVT populations that we here examine include the preoptic area (POA), the bed nucleus of the stria terminalis (BNST), the paraventricular nucleus (PVN), and the supraoptic nucleus (SON). While the PVN and SON consist primarily of large magnocellular AVT/AVP neurons known primarily for their role in the regulation of osmotic homeostasis via release into the periphery, some AVT/AVP neurons in the PVN are also known to be involved in stress-reactivity, especially when the stressors include emotionally salient stimuli (Caldwell et al., 2008, Engelmann et al., 2004, Goodson and Kabelik, 2009, Herman et al., 2003 and Landgraf and Neumann, 2004). Furthermore, studies have demonstrated the occurrence of central release from the soma and dendrites of these neurons (Landgraf and Neumann, 2004 and Ludwig and Leng, 2006). In some species, including anoles (Propper et al., 1992b), a strip of parvocellular AVT neurons also extends medially from the BNST to the preoptic area (POA); the latter is the ancestral vertebrate source for all AVT/AVP projections (Goodson and Bass, 2001, Huffman et al., 2012 and Moore and Lowry, 1998). The BNST neurons are part of the extended amygdala, a region that also includes several amygdalar nuclei (Newman, 1999), though few AVT neurons are present in the brown anole amygdala. These parvocellular AVT neurons project centrally (De Vries and Panzica, 2006 and Goodson and Kabelik, 2009). Previous research in a variety of species has demonstrated the activation of AVT/AVP neurons within the extended amygdala following positive social interactions, while negative social interactions have sometimes been shown to suppressed such activity (Goodson and Kabelik, 2009 and Ho et al., 2010). The AVT/AVP neurons of the PVN, on the other hand, primarily show increased activity during stressful situations (Goodson and Kabelik, 2009 and Ho et al., 2010). Fewer studies have demonstrated a role of AVT/AVP neurons within the SON in the regulation of social behaviors, although this AVP population has been shown to exhibit changes in IEG induction in golden hamsters or mice participating in aggressive encounters (Delville et al., 2000 and Ho et al., 2010) and some involvement of AVP in the SON has been shown on social memory (Landgraf and Neumann, 2004). Based on these published findings, we predicted that in brown anoles aggressive interactions would suppress activity in AVT neurons of the BNST and increase activity of AVT neurons in the PVN and SON, whereas sexual interactions would increase activity in the POA and BNST, and possibly SON, without affecting the PVN population. Our results only partially support these predictions.

Overall, Fos induction within AVT neurons in male brown anoles was associated with the regulation of both sexual and aggressive behaviors, with activation of the POA seeming specific to sexual behaviors and activation of the PVN relating primarily but not specifically to aggression intensity. Even though this activation of the PVN in socially stressful situations is consistent with findings in other species, the associated increase in aggressive behavior output is opposite to what has been described in other species. Fos induction within AVT neurons in the SON of male brown anoles occurred after interaction with either a conspecific male or a female. Fos induction within AVT neurons of the BNST was primarily associated with sexual behavior intensity and frequency, but surprisingly also occurred during intense aggressive interactions. This last point emphasizes a difference in AVT/AVP activation across species, as studies in songbirds have instead found that territorial aggression suppresses or at most fails to alter Fos induction with AVT neurons of the BNST. These findings demonstrate some similarities and some differences across species in the relationship between the social environment, the activity pattern across AVT/AVP populations, and exhibited social behaviors. These findings further stress the importance of differentiating the effects of varied AVT/AVP populations when examining the roles of this neuropeptide in the regulation of social behaviors.