inhibition of dopamine (DA) uptake and the increase of extracellular DA

inhibition of dopamine (DA) uptake and the increase of extracellular DA JNJ-38877605 with consequent activation of DA receptors in specific brain regions such as the nucleus accumbens (NAc) and dorsal striatum are an important but may be not an exclusive mechanism for behavioral excitation induced by psychostimulants [2 5 14 15 24 25 A typical spectrum of acute cocaine-induced arousal effects in animal models includes JNJ-38877605 locomotor activation and stereotyped behavior consisting of continuous sniffing rearing licking and gnawing. in DA clearance in the NAc of freely moving rats [24]. At high doses the effect of cocaine within the stereotyped activity became predominant [1]. It is unknown whether a strong relationship exists between the stereotypy and cocaine-induced DA uptake changes in the NAc. With this study we have used fast-scan cyclic voltammetry (FSCV) on freely moving rats to determine whether a correlation exists between the increase in the stereotyped behavior and DA uptake inhibition following cocaine (20 mg/kg i.p.) administration. The FSCV was chosen since the general characteristics of this technique allow an examination of the DA uptake kinetics without DA launch or metabolism contributions [1 28 30 Male Sprague-Dawley rats (300-350 g; Charles River Raleigh NC) were housed on a 12:12 light/dark cycle with food and water ad libitum. Rats were group housed before surgery and singly housed after surgery. All protocols were authorized by the Institutional Animal Care and Use Committee at Wake Forest University or Rabbit Polyclonal to SLC5A6. college. Rats were anesthetized with ketamine (100 mg/kg) and xylazine (10 mg/kg) and placed in a stereotaxic framework. A guide cannula (Bioanalytical Systems Western Lafayette IN) was situated above the NAc core (AP + 1.3 L+1.3 V-2.0 mm from bregma). An Ag/AgCl research electrode was implanted in the contralateral hemisphere. A bipolar stimulating electrode was lowered to the ventral tegmental area ipsilateral to the guideline cannula at 5.2 mm posterior and 1.0 mm lateral to bregma. The revitalizing electrode depth was optimized to evoke DA launch in the NAc (24 rectangular pulses 60 Hz 120 μA 2 ms/phase biphasic) monitored using a carbon dietary fiber microelectrode put through the lead cannula. The rats were separately housed and allowed to recover for 48 hrs then they were placed in the test chamber and a new carbon dietary fiber electrode was put into the NAc JNJ-38877605 core. The research and carbon dietary fiber electrodes were connected to a head-mounted voltammetric amplifier (UNC Electronics Design Facility Chapel Hill NC) attached to a swivel at the top of the test chamber. Voltammetric recordings were made in the carbon dietary fiber electrode every 100 ms by applying a triangular waveform (-0.4 to +1.2 V 300 V/s). Data were digitized (National Devices Austin TX) and stored on a computer. DA launch was evoked every 5 min with electrical stimulations (24 rectangular pulses 60 Hz 120 μA 2 ms/phase biphasic) and recognized by a carbon dietary fiber electrode. At least four stable stimulations of DA were collected and then a single dose of cocaine (20 mg/kg i.p.) or saline was injected. Stimulations and recordings were collected at 5 min intervals for 2 h following a cocaine injection. Carbon dietary fiber microelectrodes were calibrated with known concentrations of DA (2-5 μM). Calibrations were carried out in triplicate and the average value for the current at the maximum oxidation potential was used to normalize signals to DA concentration. DA uptake was identified from your clearance rate of DA following a termination of the stimulus. DA uptake was assumed to following Michaelis-Menten kinetics and the switch in DA during and after stimulated launch was match using the equation: is the activation rate of recurrence (Hz) [DA]p is the concentration of DA released per stimulus pulse and Vmax is the maximal rate JNJ-38877605 of DA uptake. The baseline value of JNJ-38877605 0.05. The amplitude of DA signal measured in rat NAc markedly improved after cocaine (20 mg/kg i.p.) injection (Fig. 1). The kinetic analysis revealed significant switch in the apparent Km with no switch in Vmaximum consistent with competitive DA transporter (DAT) inhibition. There were significant main effects for both drug (F=139.0 P<0.0001) and time (F=7.57 P<0.0001). Bonferroni post checks indicated significant effects of cocaine on DA uptake in the 5 10 15 25 40 and 60 min after injection (P<0.001) (Fig. 2A). The increase in apparent Km was maximal (about 600% of settings) within10-15 min after drug administration. No switch in the apparent Km was observed in saline-treated rats. Following cocaine administration there was a designated elevation in stereotypical behavior such as sniffing and rearing (Fig. 2B). Both drug (F=162.4 P<0.0001) and time (F=12.52 JNJ-38877605 P<0.0001) showed significant effects. Bonferroni post checks revealed significant raises in the stereotypic activity in 5 10 15 25 40 and 60 min.