Altered responsiveness to parasympathetic activation of submaxillary salivary gland in the heat-acclimated rat.

Submaxillary salivary gland responsiveness during the heat acclimation procedure (34 +/- 1 degree C) was studied in the rat. Gland responsiveness was evaluated by measuring saliva flow rate of the anesthetized animals following either parasympathetic nerve stimulation or i.v. application of pilocarpine. A thirty percent decrease in glandular responsiveness for the two modes of stimulation was measured during the first 10 days of acclimation. Following 60 days of acclimation recovery was observed. It is concluded that decreased responsiveness of the heat-acclimated gland is a glandular event. Increased saliva flow occurring at the initial phase of acclimation is apparently due to changes in the thermoregulatory center.