Effect of surgery for cannula implantation into the hypothalamus on the behaviour and neural activity of broiler chicks

Abstract

1. The effects of a surgical operation, to implant a guide cannula in the chick hypothalamus for microdialysis, on behavioural responses and neural activity in broiler chicks are described. 2. General behavioural activities (feeding, preening, sitting, drinking, cage pecking and beak wiping), open field and locomotor activity tests were conducted to evaluate the effects related to surgery in the immediate 4 d following this procedure. Perfusion of Ringer solution with high K(+) after 4 d of guide cannula implantation was used to estimate the neural activity resulting from surgery through stimulation of monoamine release by in vivo brain dialysis. 3. The results of direct behavioral observations indicated that the stress provoked by surgical guide cannula insertion caused behavioural alterations that are particularly evident in the immediate days following this procedure. Open-field tests on day 4 after surgery showed that, compared to the intact control chickens, the treated chicks had a shorter latency to ambulate and defecate, with more vocalisation. Locomotor activity was less in the treated chicks than in the controls. 4. After 4 d of guide cannula implantation, the serotonin concentration started to increase 30 min after the onset of perfusing high-K(+) Ringer solution. It reached its highest value at one hour, suggesting that the 4 d after surgery is enough to alleviate some neurochemical dysfunction resulting from surgery. The results of behavioural observations, open-field and locomotor activity tests indicate that the surgical operation caused stress and fear in chicks which persisted up to 4 d.