Serotonin and vasotocin function in territoriality.

This ethopharmacological investigation comprised a long-term field study that examined the function of serotonergic and vasotonergic systems in territoriality. Adult territorial and non-territorial (silent) male coquí frogs (Eleutherodactylus coqui) were injected (IP) with either arginine vasotocin (AVT) or one of two serotonin agonists, 5-HT2A/2C selective agonist, (±) DOI - [(±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane], or 2) the 5-HT1A selective agonist, 8-OH-DPAT - [(±)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene]. Control groups received saline injections. Each male received two injections. Following the first injection, whether AVT or a 5HT agonist, the male was observed so that behavior could be documented prior to the second injection, which consisted of the other drug class. All frogs were marked, placed back in the exact location as captured, and observed for all behaviors and vocalizations. Territoriality in E. coqui includes several behavioral components: movement into a calling site, presentation of dominant physical displays, emitting advertisement calls, and defense a territory (including the use of physical force and/or aggressive vocalizations). This investigation found that particular territorial behaviors were significantly influenced by 5HT and AVT action. Initiation of advertisement calling is activated by AVT and suppressed by 5HT, calling rate is affected by 5HT activation, presentation of dominant physical displays are activated by AVT and repressed by 5HT activation, and movement associated with activation of territorial behavior is stimulated by AVT. These data suggested that both 5HT and AVT have a profound impact on territoriality and are two fundamental neuroendocrine systems that govern territorial behavior in social systems.

Mammalian nonapeptides activate territorial behavior in an amphibian.

Arginine vasopressin (VP) and oxytocin (OT) are two nonapeptides present in mammals and execute a wide array of physiological and behavioral functions. In amphibians arginine vasotocin (VT) is hypothesized as a homologous nonapeptide for VP and also performs physiological and behavioral tasks. Studies have demonstrated that the structural and functional relationships between VP, OT, and VT receptor families are similar; however, little behavioral data has complimented these studies. The objective of this investigation was to determine if the mammalian nonapeptides VP and OT would activate behavioral manifestations naturally activated by VT. Frogs are particularly attractive for such an investigation because it is well documented that VT activates advertisement calling and territorial behavior. This investigation was a large sample size field study that utilized the territorial frog, Eleutherodactylus coqui. Fieldwork occurred on the Islands of Puerto Rico and Hawai'i and focused on territorial (calling) and non-territorial (silent) males. Frogs were administered exogenous injections of VP, OT, VT (positive control), or saline (control) in the field, placed back in their original locations, and were observed for behaviors. Exogenous injections of VP and OT significantly activated silent males to emit advertisement calls and exhibit territorial behavior. Additionally, silent males moved into new areas prior to calling whereas territorial males remained in their own territories. Control (saline) males displayed normal behaviors. This is the first study to demonstrate that mammalian nonapeptides activate calling and territorial behaviors in frogs and corroborates the close evolutionary relationships within the nonapeptide family.