Distribution of glutaminase activity in retinal layers of rat and guinea pig

The glutaminase activity in rat and guinea pig retina is twice as high in photoreceptor inner segments as in any other layer. Since the inner segments are involved in non-transmitter-related metabolic functions, it is suggested that glutaminase should not necessarily be taken to imply glutamatergic neurotransmission until the function of the high activity in regions such as the inner segments is better understood.