Abstract
Purpose::
The objective is to understand how histamine modulates the light responses and spontaneous activity of various types of amacrine cells (ACs) in the tiger salamander retina.
Methods::
Using patch electrodes filled with a K-gluconate solution, Neurobiotin and Lucifer Yellow, the voltage and current responses to light were recorded in the current (-400 pA to 400 pA) and voltage clamp (-60 mV to 60 mV) modes from ACs in tiger salamander retinal slice preparations.
Results::
In 73% of ACs, 10 µM histamine reversibly reduced the light responses and spontaneous activity. The rest of the ACs in our sample were insensitive to histamine; these histamine-insensitive ACs had narrow dendritic fields. The majority of the histamine-sensitive ACs had long, monostratified dendrites in the ON sublamina. Other histamine-sensitive ACs were medium field diffuse cells with dendrites ramifying in five or more contiguous strata of the IPL. The majority of histamine-sensitive ACs had ON-OFF light responses, and approximately half of those showed spontaneous activity. 10 µM histamine decreased both the ON and OFF light responses, but the effects of histamine were more pronounced on the ON component than on the OFF component. Histamine also decreased the firing rate of spiking cells, both in the dark and during the light responses.
Conclusions::
Histamine decreases light responses and spontaneous activity in wide field and medium field ACs but not in narrow field ACs.
Keywords: amacrine cells • electrophysiology: non-clinical • neurotransmitters/neurotransmitter systems