Central 5-HT and the respiratory response to acoustic stimulation in awake rats: Effects of PCPA, 5-HTP and 8-OH-DPAT

Abstract

It was found that PCPA (4×50-100 mg/kg) decreased the respiratory-response to tone pulses (acoustic reaction), and this effect was antagonized by the administration of 5-HTP (25 mg/kg), after inhibition of extracerebral aromatic amino acid decarboxylase by means of benserazide (25 mg/kg). A further increase in the dose of 5-HTP, 50–100 mg/kg, in animals not treated with PCPA did not significantly affect the acoustic reaction. The putative 5-HT agonist 8-OH-DPAT produced a decrease in the acoustic reaction (but also at higher doses some desynchronization of respiration with tone). The administration ofd-amphetamine, 0.5–2.0 mg/kg, resulted in an increase in the acoustic reaction. Thus, in the present experiment, using a simple sensory-motor response, 8-OH-DPAT behaves as a 5-HT antagonist and the results provide further support for mixed 5-HT receptor agonist/antagonist properties of this compound.