This paper examined the grooming effects of central injections of the tetradecapeptide bombesin (BN) in the infant rat. Anaesthetized rat pups of 1-20 days of age (n = 7/dose/age) were injected intracerebroventricularly (i.e.v.) with either BN (0.01-1.0 μg) or saline (control condition) and placed in heated test cages. Following recovery from the anaesthetic, the subsequnnt behaviour displayed by the pups was videotaped for the next 60 min. These videotaped responses were then scored for a variety of grooming and other behaviours. Pups of all ages (1-20 days) groomed in response to BN with the 1-day-old pups the least and 20-days-olds the most sensitive to BN. In the 10-days-olds, scratching, in an immature, non-contactt form, was elicited by BN. This was replaced by mature, contact type scratching in the sequence of grooming behavious at 20 days of age. Scratching activities appeared to form a subsystem connected to but nonetheless separate from washing behaviours and this was particularly distinguishable at 20 days of age. Changes in BN-induced grooming appeared to reflect the maturation of the motor capabilities of the developing rat. In conclusion, these results indicate that BN binding sites in the developing rat central nervous system (CNS) are pharmacologically functional from an early stage in ontogeny when there is little or no measurable amount of the peptide itself present in the CNS.
- Behavioural sequence
- Infant rat