Studies on the sites and mechanisms of 5-HT1A receptor-mediated in vivo actions

In the first study the possible role of the hypothalamic paraventricular nucleus (PVN) in 5-HT1A receptor agonist-induced neuroendocrine responses was tested. Surgical lesions of the PVN completely blocked ACTH and corticosterone and markedly attenuated oxytocin but not prolactin responses to ipsapirone, providing evidence for a crucial role of the PVN in these responses. In the second study we have compared the effectiveness of intracerebroventricular and intravenous administration of 8-OH-DPAT in frequently used behavioural models of 5-HT1A receptor activation, namely lower lip retraction, body temperature and tail flick responses. We have found marked differences in the rates of effectiveness. We conclude that these models measure the activation of different subsets with clearly separate location of 5-HT1A receptors.