DISSOCIATION BETWEEN ADRENAL TYROSINEHYDROXYLASE AND PHENYLETHANOLAMINE N-METHYLTRANSFERASE ACTIVITIES FOLLOWING REPEATED EXPERIENCE OF DEFEATS IN INDIVIDUALLY HOUSED MALE DBA 2J MICE/

Adrenal activities of tyrosnehydroxylase (TH) and phenylethanolamine N -methyltransferase (PNMT) were compared between individually housed de feated intruders and socially housed residents (SR) (Experiment 1), an d between individually housed defeated intruders and individually hous ed victor residents (Experiment 2). In addition, corticosterone titers were determined and dominance status of SR (dominant, subdominant act ive, and subdominant passive) considered. Defeats were induced twice a week for 6 consecutive weeks in short resident-intruder encounters. T he main findings were: 1) within the groups of SR, TH and PNMT activit ies were high in dominant and low in subdominant-passive mice; 2) in E xperiment 1, TH activities of individually housed defeated intruders w ere low like those of subdominant-passive SR whereas their PNMT activi ties were high like those of dominant SR; 3) in Experiment 2, TH activ ities were low in both categories of individually kept mice whereas PN MT activities were significantly elevated in the defeated intruders; 4 ) in both experiments, PNMT activities of intruders correlated signfic antly with the accumulated number of attacks they had received through out all resident-intruder tests. Findings show separate effects of per manent social stimulation and of episodic experience of defeats on adr enal catecholamine synthesis. Lack of permanent social stimulation dec reased adrenal TH and PNMT activities whereas repeated episodic experi ence of defeats specifically increased PNMT but not TH activities in i ndividually housed mice.