COLD-INDUCED INCREASES IN PHENYLETHANOLAMINE N-METHYLTRANSFERASE (PNMT) MESSENGER-RNA ARE MEDIATED BY NONCHOLINERGIC MECHANISMS IN THE RAT ADRENAL-GLAND

Previously, we reported that cold stress induces a rapid increase in a drenomedullary PNMT mRNA levels, followed by concomitant increases in PNMT immunoreactivity (10). In the present study, the extracellular si gnals mediating this adaptive response to stress were investigated usi ng northern analysis and RNA slot-blot hybridization. Although adrenal denervation significantly diminished cold-induced increments in adren omedullary PNMT mRNA levels, it did not completely abolish the cold st ress response. In contrast to these results, splanchnectomy completely inhibited cold-induced increments in TH mRNAs in the same tissue samp les. These findings indicate that the effects of cold exposure on PNMT mRNA levels are mediated by both neural and non-neural mechanisms, an d that adrenal PNMT and TH are differentially regulated in response to cold stress. Surprisingly, the neural component of the PNMT stress re sponse could not be attenuated by peripheral administration of chloris ondamine, a powerful nicotinic ganglionic blocking agent. In contrast, chlorisondamine was effective in inhibiting sympathetic neural activi ty, as judged by the drug's ability to completely block increases in b lood pressure, heart rate, and plasma catecholamines resulting from sp inal cord stimulation in pithed rats. The administration of atropine, a muscarinic receptor antagonist, also failed to inhibit cold-induced alterations in adrenal PNMT mRNA. These results suggest that the trans -synaptic induction of adrenal PNMT mRNA involves a non-cholinergic co mponent, and that cold-induced increases in PNMT mRNA are not coupled to acetylcholine-mediated adrenal catecholamine release.