Hello dear researchers,

I am recording LTP in the hippocampus tissue in vivo (7-8 weeks old Wistar rats-Control Groups). After applying HFS there is no or very little increase in amplitude (about 20%).

The method I use is as follows:

• The rats were anesthetized with urethane anesthesia at a dose of 1.5 g/kg intraperitoneally and the body temperature of the rats was kept constant at 37.0±0.2 °C during all procedures. The heads of the rats were fixed to the system with ear and mouth sticks and placed in the stereotaxic system (Kopf Instruments, Tjunga, CA, USA).
• The stimulus electrode was placed in the medial perforant tract (4.3 mm lateral to the midline, 8.1 mm behind the bregma), and the recording electrode was placed in the dentate gyrus (2.3 mm lateral to the midline, 3.8 mm posterior to the bregma).
• Small holes with a diameter of 0.5 mm were drilled.
• The reference screw electrode was lightly screwed into the hole drilled approximately 3 mm behind the lambda, touching the cortical surface. Stimulating and recording electrodes were mounted on the electrode holders on the left and right stereotaxic arms. The silver chloride disc electrode is placed on the tail as the ground electrode.
• The two poles of the stimulating electrode are connected to the stimulation insulator (MASTER 9, A.M.P.I, ISO Flex) with low resistance cables. Monopolar recording electrode (0.005 inch, stainless steel, Plastic One) terminal was connected to an electrophysiological differential amplifier (band-pass filter = 1 Hz – 3 kHz) (Bio Amps, ADinstruments) and data control was made with Scope” software (AD Instruments). In addition, ground and reference electrode terminals are also connected to the differential amplifier.
• The approximate depth of the recording electrode for recording the maximal area EPSP is between 2.7-3.2 mm. Baseline recordings were obtained with 0.1 ms biphasic square wave pulses at a frequency of 0.1 Hz.

Did you encounter a similar problem? Or do you have any idea where this problem might originate?