Munc18-1 haploinsufficiency results in enhanced anxiety-like behavior as determined by heart rate responses in mice.

•Heart rate (HR) responses were studied during aversive emotional challenges in mice.•Munc-18-1 heterozygous (HZ) mice had a higher tachycardia than wild-type (WT) mice.•HZ mice showed stronger tachycardia and delayed HR extinction in fear conditioning.•Basal HR dynamics including diurnal changes did not differ between genotypes.•Overall, these HR results indicate enhanced conditioned fear in munc-18-1HZ mice.