Concentration of 17 β-estradiol in the plasma of ovariectomized female rats. Ovariectomized (OVX) rats were implanted with Alzet pumps dispensing 750 ng/day of E2 or the same volume of the vehicle polyethylene glycol (no E2). OVX rats infused with no E2 or E2 were given a 30 μl intra-articular temporomandibular joint (TMJ) injection of saline or 30 μg complete Freund's adjuvant (CFA) seven days after pump implantation. Treatment groups consisted of OVX rats having their TMJ injected with saline (No E2/saline); OVX rats supplemented with E2 that had saline injected into their TMJ (E2/saline); OVX rats injected with CFA (No E2/CFA) and OVX rats supplemented with E2 that had CFA injected into the TMJ (E2/CFA). 48 h following TMJ injection the animals were sacrificed and the concentration of E2 was measured in the plasma by radio-immunoassay. The histogram shows the mean ± SEM concentration of 17 β-estradiol per ml of plasma from the pooled values of four animals per treatment group, * p < 0.05.