Salmon calcitonin induced head twitch in the rat.

Abstract

Abstract-The intracerebroventricular administration of salmon calcitonin (sCT) to rats induced a dose-dependent increase in the number of head twitches and poten tiated such a response elicited by L-5-hydroxytryptophan (L-5-HTP). Subcu taneously administered sCT was ineffective "per se" but could again potentiate the head twitch response elicited by L-5-HTP.Since these data suggest a stimulation of the brain serotonergic pathways, the obtained results support the hypothesis that some central actions of sCT may involve activation of serotonergic systems in the rat brain.should enhance this increase. Head twitches were chosen as they are a quantifiable and reliable measure of serotonergic activation: the response is dose-related and appears even in the presence of low doses of 5-HT agonists (4). Male Sprague Dawley rats (Nossan, Milano, Italy) weighing 250-300 g were used. They were housed under con trolled conditions of light (7.00 a.m.-7.00 p.m.), temperature (22+2°C) and humidity (65%) and were allowed free access to standard laboratory diet and tap water. sCT was kindly supplied by Sandoz (Basel) as commercial vials (containing 100 MRCU=20 ug of peptide, 2 mg of acetic acid, 2 mg of sodium acetate, 7.5 mg of sodium chloride and distilled water to 1 ml volume) and as pure powder. As needed, these vials were diluted with saline, and sCT was s.c. injected at the doses of 5, 10, 20, 40 and 80 /ig/kg; control rats received 4 ml/kg of saline containing ace tic acid. I.c.v. injected rats were implanted, at least 7 days before the behavioral trials, with permanent plastic cannulae entering the right ventricle. By this route, the powder form of sCT dissolved in sterile saline containing 0.5% human albumin was administered at the doses of 0.1, 0.2, 0.4 and 0.8 ug/rat; control animals received only vehicle (20 al/rat). Immediately after treatment, the rats were put into transparent plexiglas cylinders (20 cm diameter, 25 cm height), and 30 min later, the head-twitches exhibited by the animals

Relationships between the effects of peripherally administered salmon calcitonin on calcaemia and brain biogenic amines.

“…5HT agonists adminis tered to rats induce head-twitch behavior (3,4). These facts are consistent with the observations that sCT influences the release of hormones from the hypophysis (5)(6)(7)(8), in duces anorexia (9), depresses the amphet amine-induced locomotor activity (10) and potentiates the head-twitch behavior elicited by 5-hydroxytryptophan (11). Notwithstand ing, the role of the serotonergic system ac tivation in some of these effects should still be clarified.…”

“…Finally, the data obtained on the changes in the levels of monoamine neurotransmitters and metabolites in rat brain could account for some of the sCT induced behavioral effects, principally those that involve more directly the serotonergic systems as the anorectic effect (20), the inhibition of amphetamine induced hypermotility (21) and the head twitch response (11).…”

“…Moreover, it has been hypothesized that the effects mediated by hypocalcaemia also in clude changes in the functional state of the serotonergic system by which sCT poten tiates the head twitch response elicited by 5 hydroxytryptophan (11). In this regard, it is likely that many other neuronal systems, besides the serotonergic system, should be influenced by hypocalcaemia.…”