Effects of neural blockers on stimulated tear volume. (a) Tear volume above baseline for gland stimulation (6 mA, 500 μs pulses repeated at 30 Hz for 5 min) with scopolamine (1.5 mg kg−1, n=5), prazosin (2.0 mg kg−1, n=5), hexamethonium(10 mg kg−1, n=7) and no blockers (control, n=10). Scopola-mine blocked the efferent parasympathetic pathway. Hexamethonium did not affect tearing; suggesting afferent nerves were not involved. (b) Tear increase over baseline for afferent nerve stimulation with hexamethonium (10 mg kg−1) and without (control). Hexamethonium blocked tearing from corneal (6 mA, 500 μs pulses at 30 Hz for 10 s, n=6) and ethmoid nerve (2–3 mA, 200 μs pulses at 30 Hz Hz for 5 min, n=5) stimulations: *p ≤ 0.01, compared to control.