Fig. 5.

Recordings from corneal cold receptors in guinea pig and mouse corneas show no response to light. (A, B) Sample recordings of nerve terminal impulse (NTI) activity in response to a cooling ramp (from 34 to 20°C) of cold thermoreceptors recorded in a guinea pig (A) and a mouse cornea (B), performed in light condition. Once firing rate and temperature returned to baseline, the cornea was kept in darkness for 15 min. The upper traces plot the instantaneous frequency in Hz. The middle traces plot the time course of the NTI activity (in impulses/s). The lower traces display the temperature value measured at the perfusion chamber, near the corneal surface (in °C). (C, D) Effects of light on ongoing NTI activity at basal temperature (34°C) of cold thermoreceptors recorded in a guinea pig (C) and a mouse cornea (D). The second traces plot the instantaneous frequency in Hz, showing no differences in rhythmic firing pattern of the units under dark and light conditions (upper traces). The third and lower traces plot ongoing NTI activity (in impulses/s) at constant, basal temperature (lower traces). Time scales are 100 s.