Plasma enkephalin-like peptide response to chronic nicotine infusion in guinea pig.

Nicotine administration, using mini-osmotic pumps, to male guinea pigs (31 micrograms/h for 10 days) resulted in a significant elevation of plasma epinephrine and enkephalin-like peptides but not norepinephrine. The increase in plasma epinephrine and enkephalin-like peptides was not accompanied by corresponding alterations in either adrenal medullary synthesis or blood pressure and heart rate. These findings may provide a partial explanation for the observation that chronic smoking does not induce hypertension.