Inhibition of rat brain tryptophan hydroxylation with p-chloroamphetamine

Dopamine receptor blockade by imidoline and its proposed active conformation

Imidoline, 1-[2-(N,N-dimethylamino)ethyl]-3-m-chlorophenyl-2-imidazolidinone, has been found to be as potent as chlorpromazine in increasing striatal DOPA accumulation and prolactin secretion in vivo. In contrast, imidoline exhibited only weak inhibitory activity towards dopamine-sensitive adenylate cyclase and 3H-spiroperidol binding to striatal membranes in vitro. These neuroleptic effects in vivo are probably caused by blockade of dopamine receptors since imidoline did not deplete the striatum of dopamine. Imidoline is of interest because its structure is distinct from those of other neuroleptics. A proposed active conformation involves intramolecular hydrogen bonding between the protonated dimethylamino group and the oxygen of the imidazolidinone ring. The spatial relationship between the amine nitrogen and phenyl ring in this conformation allows proper fit of imidoline with key dimensions described for the dopamine receptor.

Influence of p-chloroamphetamine on female sexual reflexes and brain monoamine levels

The effect of p-chloroamphetamine(PCA) on female sexual reflexes was biphasic. Administration of PCA to receptive females initially terminated ongoing sexual behavior and this effect was correlated with the release of monoamines, particularly serotonin (5-HT). Sexual reflexes were abolished within 15 min of PCA injection. Other reflexes, including reciprocal forepaw treading, lateral head weaving, hindlimb abduction and Straub tail, were elicited by PCA. The long term infuence of PCA was the opposite. A facilitation of female sexual behavior occurred accompanied by a relatively specific depletion of 5-HT (10 mg/kg, 66% depletion; 20 mg/kg, 80% depletion) with both dopamine and norepinephrine depleted by less than 15%. This long term facilitation of female sexual reflexes was not blocked by dexamethazone suggesting that PCA was acting directly on the neural substrate for mating and did not produce it facilitation via adrenal progesterone. This biphasic infuence of PCA on mating reflexes, paralleling its effect on monoamine transmission, suggests serotonergic involvement in the integration of mating behavior.