Biology session

The term ’designer drug’ or ’party drug’ refer to a group of synthetic substances that are pharmacologically and structurally very similar to an illegal substance. Due to the easy accessibility via the Internet, they spread rapidly among teenage people and young adults. Although widely abused, there is a conspicuous lack of epidemiological, animal and clinical data concerning designer drugs. Here we present data on the effect of the synthetic cathinone derivatives mephedrone and butylone (MBDB, N-Methyl-1-(3,4-methylenedioxyphenyl)-2-butanoic hydrochloride) on neurogenesis, behavior and early adaptive learning of domestic chicks.

The key questions in our experiment were as follows: 1. What are the effects of these drugs on the developing embryo, particularly on neurogenesis? 2. What are the effects of synthetic cathinones on behavior? 3. Do the exposure to these drugs affect the learning ability in tasks focused on striatal brain regions?

To investigate the effect of prenatal exposure of mephedrone on neurogenesis we injected mephedrone (2 mg/kg egg weight) into incubated chicken eggs at critical stages (day 6 or 10) of striatal development. This was followed by quantitative analysis of post-embryonic proliferating neurons in the subventricular zone of the striatum, based on incorporation of the labeled nucleoside bromo-deoxy-uridine (BrdU), visualized by immunohistochemistry, and quantified by stereological method. A decrease in the density of BrdU-labeled cells in the subventricular zone of ventrobasal telencephalon was observed primarly in those birds injected in ovo in the later phase of striatal neurogenesis (day 10 of incubation).

To investigate the effect of mephedrone and butylone on resistance to stress, we implied social isolation and counted the number of distress vocalizations. The birds injected with mephedrone (10 mg/kg b.w. i.p.) elicited an increase in the number of distress calls in the first 5 min of the test, as compared to the control group. In the case of butylone (10 mg/kg b.w.) no significant difference was observed, but the general physical status of the animals did not allow the undisturbed execution of the isolation test. Butylone (10 mg/kg b.w. i.p.) caused coordination disorders with loss of postural control and was accompanied by strong hyperventillation. Applying the same dose of mephedrone these effects were not observed.

To investigate the effect of mephedrone on learning ability, one-day old chicks injected with mephedrone (10 mg/kg b.w. i.p.) were tested for the passive avoidence learning task. No impairment of memory retention was evident when the drug was administered 30 min prior to training. The drug-injected birds showed hyperactivity without apparent distress at the time of recall.