Influence of bombesin on neuronal hypothalamic thermosensitivity during the early postnatal period in the Muscovy duck (Cairina moschata)

The influence of bombesin (1 μg/0.1 ml artificial cerebrospinal fluid) on neuronal thermosensitivity of the preoptic area of the anterior hypothalamus in brain slices of 5- ( n =7 neurons) and 10-day-old ( n =36 neurons) Muscovy ducks ( Cairina moschata ) was investigated. Similar to adult mammals, most of the neurons investigated increased the firing rate (FR) after bombesin application. Changes in FR were not related to changes in thermal coefficient (TC). The neurons react to bombesin also under synaptic blockade. The bombesin-induced effect on TC (increase or decrease in nearly the same number of neurons, e.g. nine neurons increased and ten decreased TC in 10-day-old ducklings) in the postnatal bird neurons investigated was different from the results described in adult mammals, where the main reaction to bombesin was an increase of TC in warm-sensitive and temperature-insensitive-neurons and a transformation of temperature-insensitive-neurons into warm-sensitive ones. This may be related to the assumption that during early ontogeny, body functions react to exogenous and endogenous factors nonspecifically. It is to speculate, that later, probably at the end of embryonic development or during the early postnatal period, the reactivity of these functions changes qualitatively, so that the reaction of an individual function to different factors becomes specific (ultimately adaptive).