5-HT1A and 5-HT2 receptors mediate discrete behaviors in the Mongolian gerbil

Although the ability of agonists at specific serotonin (5-HT) receptor subtypes to induce distinct behaviors has been well documented in the rat, similar studies have not been reported in the Mongolian gerbil. We have found that the 5-HT1A/5-HT2 agonist 5-methoxy,N-N dimethyltryptamine (5-MeODMT) (0.5-8 mg/kg, SC), the specific 5-HT1A agonist 8-hydroxy(di-n-propylamino)tetralin (8-OH-DPAT) (0.125-16 mg/kg, SC), and the 5-HT precursor L-5-hydroxytryptophan (L-5-HTP) (100-250 mg/kg, SC) all elicit a 5-HT syndrome in the gerbil. This syndrome, analogous to the 5-HT syndrome in the rat, consists of reciprocal forepaw treading (RFT), hindleg abduction (HA), body tremors (BT), and Straub tail (ST). The putative 5-HT1A antagonist NAN-190 (0.25-8 mg/kg, SC) when dosed 15 min prior to either 5-MeODMT (4 mg/kg, SC) or 8-OH-DPAT (16 mg/kg, SC) blocked both RFT and HA in a dose-dependent manner, suggesting these 5-HT syndrome behaviors are mediated via 5-HT1A receptor activation. We also identified a unique, dose-responsive behavior in the gerbil, induced selectively by 5-HT1A agonists such as quipazine (2-16 mg/kg, SC) and (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.125-8 mg/kg, SC). This reciprocal hindleg body scratch (RHBS) behavior is dose dependently inhibited by pretreatment with the selective 5-HT2 antagonist ritanserin (0.0125-0.2 mg/kg, SC). RHBS behavior is also potently inhibited by pretreatment with the selective 5-HT1A agonist 8-OH-DPAT (0.005-0.04 mg/kg, SC), demonstrating a 5-HT1A/5-HT2 receptor subtype interaction.(ABSTRACT TRUNCATED AT 250 WORDS)