The present longitudinal analysis was aimed at assessing (i) the effects of developmental capsaicin (CAPS) administration on nociceptive responsivity and on the response of adult mice to social stimuli; (ii) the action of NGF on the ontogeny of the same nociceptive response and social stimuli; (iii) whether capsaicin treatment could be reversed by subsequent treatment with NGF. CD-1 mouse pups were treated with either capsaicin (50 mg/kg, s.c.) or vehicle on postnatal days (PNDs) 5 and 8. Every other day from PND 9 to PND 21 the same pups received a daily injection of NGF (0.75 mg/kg, s.c.). During both the prepuberal stage (PNDs 14, 21, and 28) and adulthood, mice were repeatedly tested in a hot-plate apparatus (52 +/- 0.1 degrees C for 1 min). At adulthood they also underwent an aggressive behaviour test. NGF-treated mice showed a shorter latency to hindlimb licking response in the hot plate compared to both controls and NGF-CAPS groups. CAPS-treated subjects showed a long-lasting hypoalgesia at both prepuberal and adult stages that was not modified by subsequent NGF treatment. Finally, NGF-treated mice were more aggressive than both controls and CAPS-NGF animals.