Proinsulin C peptide obviates sympathetically mediated suppression of splenic lymphocyte activity in rats

To investigate whether proinsulin C peptide influences sympathetic nerve activity directly or indirectly through parasympathetic nerve activity.

The proliferative response of splenic lymphocytes to Concanavalin A (ConA response) which is known to be suppressed by subjection of rats to footshock or intracerebroventricular injection of corticotropin-releasing factor through sympathetic nerve activation was measured. Effect of C peptide alone or before subjection to footshock or injection of corticotropin-releasing factor was examined.

Intraperitoneal injection of C peptide was without effect on the basal ConA response, while subjection to footshock or injection of corticotropin-releasing factor lowered it. In contrast, prior injection of C peptide obviated the footshock and corticotropin-releasing factor-induced suppression of the response. When given intracerebroventricularly, C peptide was also effective at much smaller doses. Prior injection of atropine cancelled the C-peptide effects.

Our results indicate that C peptide counteracts the sympathetic nerve-mediated suppression of splenic lymphocyte proliferation in an atropine-sensitive manner. Thus, C peptide probably activates the parasympathetic nervous system through the afferent mechanism, that in turn antagonizes the sympathetic nerve-mediated suppression of splenic lymphocyte functions.