Simple Method for Fabricating Slender Infusion-Recording Assembly in 30-Gauge Syringe Needle

A device with both infusion and recording components is commonly used to evaluate neuronal responses to neuropharmacological actions in situ. With increasing demand for such devices, many designs have been reported. However, the recording and injection channels are usually limited, and their combination often involves glue, resulting in rough and uneven surfaces. Here, we report the development of a simple method for fabricating a slender infusion tube assembled with recording microwires in a 30-gauge syringe needle. There are four major advantages of the proposed infusion-recording assembly over previously reported models: (1) the small diameter of the infusion cannula minimizes the total volume of the assembly; (2) no extra glue or attachment is needed on the outside so the surface of the assembly remains smooth; (3) the microwires are flexible to allocate and their tip location can be recognized; (4) a larger guide tube can be used (e.g., a 27-gauge needle) to contain more microwires or cannulae if needed. We used this assembly to simultaneously record neuronal activities in response to local deliveries of lidocaine, which caused immediate suppression of neuronal activities that recovered after 15 min. This study shows the manufacture of the infusion-recording device and the successful application of the easy-to-make, inexpensive, and reliable assembly for neuropharmacological studies.