Sudomotor function and sweat gland innervation in galanin knockout mice

The presence of galanin and galanin binding sites in sweat gland has been demonstrated previously. In order to investigate whether galanin can influence sweat gland function, we compared sweating induced in footpads of wild type and galanin knockout mice by cholinergic and thermal stimulation using the silicone impression technique. Pilocarpine injections resulted in a similar number of reactive sweat glands and non-significant difference in the amount of sweat secretion in wild type and galanin knockout mice. However, thermal stimulation led to a significant increase in the number of secreting sweat glands in galanin knockout mice. To further evaluate possible differences in the innervation of sweat glands that could explain differences in their secretory activity, immunohistochemical labeling of cutaneous and sudomotor innervations against protein gene product 9.5, vasoactive intestinal polypeptide and choline acetyltransferase in plantar pads was performed. Immunohistochemical analysis revealed no significant differences in the distribution and intensity of the innervations between wild type mice and galanin knockout mice. Although our results indicate normal cholinergic responses and innervation of the sweat glands in galanin knockout mice, they also demonstrate that galanin plays a role in regulating the sudomotor activity in response to thermal stimulation.