BIOTELEMETRIC MONITORING OF STRIATAL NEUROCHEMISTRY AND BEHAVIOUR IN MPTP-INDUCED RAT MODEL OF PARKINSON’S DISEASE

In this study we present the real-time monitoring of four striatal neurochemical species in conscious rats using implantable amperometric sensors interfaced to a biotelemetric device. The new system, derived from a previous design [1, 2], was coupled with carbon-based microsensors and platinum-based biosensors for the detection of ascorbic acid (AA), oxygen, glucose and lactate in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a microcontroller unit, and sent to a personal computer by means of a miniaturized transmitter. A movement/vibration sensor was integrated in the electronics allowing the simultaneous study of behavior and striatal neurochemistry. The electronics was calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. Adult male Wistar rats (270-350 g) were uses in this study. Animals were housed under controlled conditions of temperature and light until stereotaxic surgery, performed under chloral hydrate anesthesia. Microsensors or biosensors were then inserted in the right striatum and the biotelemetric device fixed to the skull. The monitoring started 24 h after surgery and neurochemical and movement data were continuously recorded for three days. Systemic MPTP was administered for three consecutive days (day 1: 25 mg/Kg; day 2: 15 mg/Kg; day 3: 10 mg/Kg; i.p.) while controls received the same volume of vehicle (2.5 ml). Both glucose and lactate currents increased after the first MPTP dose (day 1) but while the glucose baseline decreased day-by-day the lactate current increased as the oxygen one. AA signal increased after each MPTP administration. The amount of spontaneous movement decreased after the single MPTP dose. The in-vivo results mainly confirmed previously-published observations on striatal AA, glucose and lactate dynamics recorded in tethered rats using microdialysis suggesting energetic impairment and activation of AA/glutamate hetero-exchange [3]. This new experimental approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs or neurotoxins on neurochemical systems.