A simple, sensitive method for the determination of extracellular catecholamines in the rat hypothalamus using in vivo dialysis

The design, construction and characterisation of a dialysis probe suitable for perfusing any deep brain structures is described. Using high-performance liquid chromatography with electrochemical detection (HPLC-ECD) the effects of flow rate, concentration, dialysate composition and temperature on the recovery within the dialysate of authentic catecholamines are detailed. The dialysis probe was used to collect endogenous catecholamines from the anterior hypothalamus of urethane-anaesthetised rats. Following organic phase extraction of the in vivo samples, a small basal release of noradrenaline (NA) of 37 +/- 4 pg/30 min sample was found. Potassium stimulation markedly elevated the release of NA and dopamine from the anterior hypothalamus in a calcium ion and dose dependent manner. It appears therefore that the dialysis probe described here, in conjunction with HPLC-ECD, can be used to follow changes in neuronally released catecholamines within the anterior hypothalamus, providing a valuable tool to study the role of these neurotransmitters in physiological and pharmacological function.