Effects of centrally administered corticotropin-releasing factor (CRF) and alpha-helical CRF on the vocalizations of isolated guinea pig pups.
Intraventricular corticotropin-releasing factor (CRF) was administered to guinea pig pups both with a freehand injection technique and via indwelling cannula. Behavioral effects depended upon the technique used. The highest dose of CRF (5 micrograms) inhibited the vocalizing of pups in a subsequent isolation test only when CRF was given by freehand injection. The possibility that disturbance attendant to the freehand procedure can account for this difference is discussed. To determine the effect of endogenous CRF in the absence of additional disturbance, the CRF antagonist alpha-helical CRF (ahCRF) was administered with the indwelling cannula procedure. ahCRF enhanced vocalizing during the first 10 min, and enhanced locomotor activity during the last 10 min, of a 30-min isolation test. Overall, the results indicate that endogenous CRF reduces vocalizing and locomotion during social isolation and that under certain injection conditions exogenous CRF can exacerbate the behavioral effect. The results also demonstrate the potential impact of the technique used to administer exogenous CRF. Further, the prevailing view, that CRF mediates stress-related behavioral responses, is supported only if behavioral inhibition, rather than vocalizing or locomotor activity, is viewed as the stress-related response in this situation.