Temperature responses and other effects of 5‐hydroxytryptophan and 5‐hydroxytryptamine when acting from the liquor space in unanaesthetized rabbits

Abstract

1 In unanaesthetized rabbits 5-hydroxytryptophan (5-HTP) and 5-hydroxytryptamine (5-HT) were injected into the cisterna magna or into the cannulated left lateral cerebral ventricle while rectal temperature was recorded. 2 5-HTP injected intracisternally in a dose of 1·5–3 mg produced a fall in temperature often followed by a rise beyond the pre-injection level. With 6 mg the main effect was a rise in temperature. The intraventricular injection of 1–2 mg 5-HTP usually produced a fall followed by a rise. 3 5-HT injected intracisternally in a dose of 0·2 mg produced a fall in temperature similar to that produced with this dose injected intraventricularly. Following an intracisternal injection of 1–4 mg 5-HT there was either a fall, or a fall followed by a rise, but in a few experiments the effect consisted mainly of a rise in temperature. 4 Additional effects regularly observed with these injections were tachypnoea, ear twitching, rapid movements of the vibrissae, shaking of the head, wiping and scratching movements, ataxia, nodding and sideways movements of the head and long-lasting catalepsy. 5 The sites where 5-HTP and 5-HT act when producing the temperature responses and the various behavioural effects are discussed.