Hyponeophagia in the Roman rat strains: effects of 5-methoxy-N,N-dimethyltryptamine, diazepam, methysergide and the stereoisomers of propranolol.

The effects of 5-MeODMT (2.5 mg/kg), diazepam (1 mg/kg), methysergide and the stereoisomers of propranolol (6 mg/kg) on hyponeophagia were studied in both sexes of the Roman strains of rats, selectively bred for acquisition of a two-way conditioned avoidance response. Diazepam, methysergide and 1-propranolol increased feeding in a novel environment whilst 5-MeODMT decreased it and d-propranolol was inactive. Several strain differences in drug responsiveness occurred, the Roman Low Avoidance subjects being most sensitive to all drugs tested as well as being most neophobic. A sex difference in 5-MeODMT sensitivity was also found, female rats of the Roman High and Control Avoidance strains being more sensitive than males. The findings are discussed in connection with differences in arousal and biochemical parameters between these strains.