Drinking behaviour induced by intracranial injections of eledoisin and substance P in the pigeon

Abstract

THE only peptide known which rapidly and consistently elicits a specific behavioural response when injected into the brain is angiotensin II, which in picomole doses causes reptiles, birds and mammals to seek out and drink water¹. But, there is evidence to suggest that other peptides such as substance P may also participate in the control of brain function and behaviour. Substance P is distributed throughout the mammalian peripheral and central nervous system, particularly in myenteric plexus, sensory afferent pathways, hypothalamus and substantia nigra². In the human brain regional concentrations as high as 0.5 × 10⁻⁹ mol per g wet tissue have been reported³. Substance P is a member of a family of peptides with similar pharmacological properties and which also includes eledoisin, an undecapeptide obtained from the salivary glands of certain Mediterranean cephalopods⁴. These peptides share a similar amino acid sequence at the C-terminal end (Fig. 1). Both eledoisin and substance P stimulate nerve cell activity in vertebrates and invertebrates and may act as regulators of neural activity⁵, but no specific behavioural effect of these peptides has yet been reported. We report here that eledoisin and substance P elicit vigorous drinking when injected into the brain of conscious pigeons.