Increment of calmodulin in proportion to enhancement of non-nicotinic responses after preganglionic stimulation of the dog cardiac sympathetic ganglia.

The possible involvement of calmodulin in ganglionic function was investigated. Drugs were given directly into the cardiac sympathetic ganglia through the right subclavian artery (i.a.), unless otherwise stated. Positive chronotropic responses to angiotensin II (0.1 and 0.2 micrograms) were enhanced after repetitive high frequency preganglionic stimulation to the right stellate ganglion. After the stimulation, positive chronotropic responses to bethanechol (2.5, 5 and 10 micrograms), but not those to dimethylphenylpiperazinium (2.5, 5 and 10 micrograms), also were enhanced. The enhancement of response to angiotensin II was not affected by i.v. pretreatment with hexamethonium (40 mg/kg) plus atropine (1 mg/kg) or nifedipine (1 mg/kg). Responses to angiotensin II were not enhanced by A23187 (0.3 mg). The enhanced response to angiotensin II after the stimulation was reduced by the calmodulin antagonists, trifluoperazine (0.1, 0.2 and 0.4 mg) and by N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (0.5, 1 and 2 mg), but not by promethazine (1 mg) and N-(6-aminohexyl)-1-naphthalenesulfonamide (0.5, 1 and 2 mg). The enhanced response to bethanechol after the stimulation also was inhibited by N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide. Pretreatment with N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide before the stimulation prevented development of the enhancement in responses to the peptide. The inhibition of endogenous protein synthesis by cycloheximide, 2.5 or 5 mg/kg i.v. 6 hr before surgical procedures, strongly inhibited development of the enhancement in responses to angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)