Quantitative genetic variation for heart rate and headless behaviors. G. Gibson , K. Ashton , R. Carrillo. Dept Genetics, North Carolina State Univ, Raleigh, NC.

   Similarities in the pharmacology and genetics of monoamine neurotransmitter function between flies and vertebrates suggest that heart rate and a range of locomotor activitites may be modeled as complex multifactorial traits in Drosophila. There is extensive genetic variation for heart rate in prepupae. We will describe a Deficiency screen performed to identify regions of the genome that have haploinsufficient effects on heart rate, which is consistent with the hypothesis that monoamines may be involved in the regulation of heart rate. Also, as shown by Hirsh and colleagues, upon replacement of the head of an adult with a droplet of one of the monoamines (dopamine, serotonin, or octopamine), decapitated flies will increase the frequency of spontaneous activities such as grooming, and in some cases begin walking around. Standard lab strains such as Oregon R are relatively inactive upon initial decapitation, but there is extensive genetic variation in natural populations affecting several headless activities, including grooming, quivering, grasping, the ability to self-right, and the response to monoamine application. Quantitative genetic dissection of this variation is feasible using Deficiency complementation tests, but requires careful control of the genetic background. We are working toward allelic association tests analagous to those being performed in human clinical studies of psychological disorders, with monoamine receptors and biosynthesis enzymes as candidate genes.