The animals were housed in individual stainless steel cages with free access to a standard sodium diet (Guabi Rat Chow, Paulinia, SP, Brazil), water and 0.3 M NaCl solution. The positions of the bottles containing water and 0.3 M NaCl were rotated daily to avoid place preference. Rats were maintained in a room whose temperature was controlled at 23 ± 2 °C and humidity at in a 12-h light/dark cycle with lights on 7:30 a.m. The animals were randomly divided into two groups: the control group (CN) and the periodontal disease group (PD). Under general anaesthesia (a mixture of ketamine (80 mg/kg of
body weight (b.w.), Cristália, Brazil) and xylazine (7 mg/kg of b.w., Agener, Brazil)) injected subcutaneously, a sterile silk Roscovitine cost ligature (strength 4/0) was tied in the cervical region of the mandibular first molars teeth bilaterally in the PD group using a technique that was previously described.9 The ligatures served UK-371804 cost as a retention device for oral micro-organisms. Ingestion of 0.3 M NaCl and water (ml/24 h) was measured 3 and 16 days after experimental ligature-induced periodontal disease in order to verify the systemic conditions of the animals. On the 15th day after ligature placement, control rats (without ligature) and rats with PD were anaesthetised with i.p. injection of ketamine (80 mg/kg of b.w.) combined with xylazine (7 mg/kg of b.w.)
and placed in a stereotaxic instrument (Kopf, Tujunga, CA, USA). The skull was levelled between bregma and lambda. Stainless steel guide-cannulas (12 mm × 0.6 mm outer diameter (o.d.)) were implanted bilaterally into the LPBN using the following coordinates: 9.2 mm caudal to bregma, 2.2 mm lateral to the midline and 3.8 mm below the dura mater. The tips of the cannulas were positioned 2 mm above each LPBN. The cannulas were fixed to the cranium using dental acrylic resin and jeweller screws and were filled with 30-gauge metal obturators
between tests. After the surgery, only control rats received a prophylactic dose of the antibiotic penicillin (30,000 IU). All animals were allowed to recover for 5 days before starting ingestion tests and during this period they had free access to standard sodium diet, water and 0.3 M NaCl solution. Tryptophan synthase Bilateral injections into the LPBN were made using 5-μl Hamilton syringes connected to 30-gauge injection cannulas by means of polyethylene tubing (PE-10). At the time of testing, the obturators were removed and the injection cannula (2 mm longer than the guide cannula) was carefully inserted into the guide cannula. For bilateral injections, the first injection was performed on one side, the needle was removed and repositioned on the contralateral side and then the second injection was given. Therefore, injections were given ∼1 min apart. The injection volume into the LPBN was 0.2 μl on each site. The obturators were replaced after the injections, and the rats were put back into their cages.