Fig. 3.
The hyperpolarizing response of PGN neurons to HA is mediated by H2-histaminergic receptors. (A) application of HA to this PGN neuron in a solution containing diphenhydramine (2 μM) to block H1 receptors and thioperamide (2 μM) to block H3 receptors resulted in the typical inhibitory response. The bath also contained 2 μM prazosin, 2 μM yohimbine, 50 μM propranolol, 5 μM methylsergide, and 1 μM scopolamine to ensure that stimulating the receptors of other modulatory systems did not mediate this effect of HA. (B) Bath application of the H2 antagonist tiotidine (20 μM) in the presence of diphenhydramine and thioperamide blocks the hyperpolarizing response to HA (same cell as in A).