A small study in six rhesus monkeys gave daily injections of various brain peptides, including DSIP, for ten days. The researchers found that DSIP and a related enkephalin seemed to hurt short‑term memory, while another peptide (alpha‑MSH) slightly improved it. There were also sex‑related differences in learning and pain response, hinting that hormones might interact with these peptides.

In a within-subject design, six rhesus monkeys (3 males and 3 females) received a 100 micrograms/kg injection of one of seven neuropeptides or a diluent control solution and were then tested for activity level, learning (discrimination reversal), short-term memory (delayed response), and for responsiveness to noxious stimuli. One daily injection was made with a different peptide for 10 consecutive days, including pre- and post tests on th first and last days with the diluent control. DSIP and D-Phe4-Met enkephalin seemed to produce some interference with short-term memory, while alpha-MSH showed some facilitation of it, as indicated by interactions of the peptides with the delay periods of 0, 15, or 30 sec. Sex differences were found in the learning task and the responsiveness to a noxious stimulus, suggesting the possibility of interactions between the peptides and endogenous hormones.