[Electrophysiological characteristics of neurons in rat substantia nigra by visual patch clamp technique]

To establish the brain slices of substantia nigra and striatum in rats and study the properties and functional significance of substantia nigra neurons.

The technique of infrared differential interference contrast (IR-DIC) and CCD-Camera system with visual patch clamp whole-cell recording were combined. One hundred healthy substantia nigra neurons were located and the measurements of active potential and Ih current recorded and analyzed.

Visual patch clamp technique could be used to make a direct localization of substantia nigra and to identify the active neurons. Spontaneous active potential was shown in 94/100 neurons. Among them, 85 (Group A) had a frequency less than 10 Hz and 9 more than 10Hz (Group B). The means were (5.0 +/- 2.7) Hz and (14.0 +/- 2.6) Hz. respectively. As compared with the former, the latter had no obvious hyperpolarization during active potential period. Apparent hyperpolarizing current could be induced in 92.9% (79/85) of Group A neurons (-120 mV, 47.5 pA +/- 5.8 pA). They were classified as dopaminergic neurons. However, the Group B neurons had no or little Ih current and were classified as GABA neurons (P < 0.001).

The types of nigra neurons can be distinguished by observing the fundamental electrical characteristic of dopaminergic neurons in nigrostriatal brain slices under visual inspections. And it may provide rationales for an in-depth knowledge of the occurrence and transmission of signal pathways between substantia nigra and