An analysis of stereotyped behaviour in Mastomys natalensis

The stereotyped behaviour was analysed in Mastomys natalensis, a species of desert rat recently introduced in laboratory practice. The components of stereotyped behaviour were similar to rat characterised by repetitive sniffing, rearing, licking, head movements and biting. Apomorphine (0.5-2.0 mg/kg), amphetamine (2.5-10 mg/kg), methylphenidate (10-30 mg/kg) and adamantanamine (10-50 mg/kg) administered intraperitoneally, induced stereotyped behaviour in dose-dependent manner. Positive response was also obtained by other drugs acting on dopamine receptors like l-dopa, GBR 12909, piribedil, tyramine, BS 9648, BS 9641 and BS 8824. Yohimbine (2 mg/kg) failed to produce any response. Apomorphine (2 mg/kg), amphetamine (10 mg/kg), methylphenidate (30 mg/kg) and piribedil (12 mg/kg) induced stereotypy which could be blocked by dopamine receptor blockers haloperidol (1 mg/kg) or pimozide (1 mg/kg) but yohimbine (2 mg/kg) an alpha adrenoceptor blocker was ineffective. Adamantanamine, piribedil and GBR 12909 enhanced the stereotypy induced by low doses of apomorphine, amphetamine and methylphenidate. The data shows that the stereotyped behaviour in Mastomys natalensis is mediated through dopaminergic mechanisms. It appears that both excitatory and inhibitory types of dopamine receptors are involved.