IN-VITRO RELATION BETWEEN PREGANGLIONIC SYMPATHETIC-STIMULATION AND ACTIVITY OF CUTANEOUS GLANDS IN THE BULLFROG

1. Activation of cutaneous glands was studied by measuring changes in transepithelial potential (TEP) after pre- and postganglionic sympathe tic stimulation in the bullfrog, Rana catesbeiana. 2. In normal Ringer solution, TEP was 20-90 mV with the basolateral (inside) surface posi tive. Single shocks to the preganglionic B pathway decreased TEP by up to 3 mV. Cutaneous depolarizations had a latency of 1.2 s, a rise tim e of 2.5 s, and decayed with an exponential time constant of 15 s. Sim ilar depolarizations were evoked by postganglionic stimulation. 3. Cut aneous depolarizations summed during repetitive stimulation at >0.05 H z. For trains of three stimuli, peak amplitude increased with frequenc y and saturated at 2 Hz. In some preparations, longer trains evoked po lyphasic changes in TEP. Preganglionically evoked cutaneous responses were abolished by (+)-tubocurarine. Postganglionically evoked cutaneou s depolarizations were antagonized by phentolamine, but not propranolo l. 4. Repetitive preganglionic stimulation of the C pathway (>100 at 2 0 Hz) evoked little change in TEP and did not modulate depolarizations evoked through the B pathway. In nicotine, peptidergic cotransmission was enhanced in the ganglia, and repetitive C pathway stimulation evo ked cutaneous depolarizations whose time course mirrored that of the p ostganglionic peptidergic after-discharge. The after-discharge and ass ociated cutaneous depolarization were blocked by a luteinizing hormone -releasing hormone antagonist. 5. The results show cutaneous glands ar e selectively innervated by B neurones and respond to low levels of ne ural activity. Asynchronous postganglionic firing mediated by peptider gic cotransmission can provide a basis for heterosynaptic interactions between the B and C pathways.