Differential Influence of Rearing Conditions and Methamphetamine on Serotonin Fibre Maturation in the Dentate Gyrus of Gerbils <i>(Meriones unguiculatus)</i>

Abstract

Environmental experience and drugs are two parameters that affect the maturation of neurotransmitter systems. The influence of impoverished rearing (IR) versus enriched rearing (ER) was compared in conjunction with postnatal methamphetamine (MA) treatment. The densities of immunostained 5-HT fibres were quantified in septal and temporal regions of the hippocampal dentate gyrus (DG) in young adult gerbils. In the IR group, 5-HT fibre densities were significantly increased in the molecular, granular and polymorphic layers of the DG in the temporal plane. After postnatal MA treatment, the 5-HT fibre density in the ER group reached a level equivalent to that of the IR group in nearly all respects. Under IR conditions, the pharmacological intervention significantly increased the maturation of fibre densities in septal layers only in the right hemisphere with no significant alterations in the left hemisphere and in temporal regions of either hemisphere. According to our previous studies on hippocampal neurogenesis, adaptations of 5-HT fibre densities partly proved to be positively correlated to cell proliferation rates for each of the specific conditions. Thus, the induced MA sensitivity, caused by pharmacological intervention at day 14, was manifested as direct interaction of 5-HT fibre maturation and cell proliferation in dependence of environmental factors. Both IR and MA together give us a better understanding of raphe-hippocampal plasticity and offer new perspectives for pharmacological studies on the 5-HT participation in mental disorders.

Comparison of monoamine and corticosterone levels 24 h following (+)methamphetamine, (+/–)3,4‐methylenedioxymethamphetamine, cocaine, (+)fenfluramine or (+/–)methylphenidate administration in the neonatal rat

“…For example, MA administration from P11-15, but not P16-20, is sufficient to cause deficits in spatial learning (Williams et al 2003b). In addition, a single exposure of MA on P14 in gerbils has been shown to cause alterations in behavior, neuroanatomical structure and neurotransmitter content (Dawirs et al 1996;Blaesing et al 2001;Busche et al 2002;Neddens et al 2002), suggesting that even a single day of exposure is enough to perturb some aspects of neurodevelopment.…”

Offer and demand: proliferation and survival of neurons in the dentate gyrus

“…Cocaine, too, reduces dentate CP (Yamaguchi et al ., 2004). However, because there are only very few DA fibres in the HC (Yoshida et al ., 1988; Gasbarri et al ., 1997), dopaminergic drugs seem to exert their effect mainly in the prefrontal and entorhinal cortices, which then influence the DG via their glutamatergic efferents (Dawirs et al ., 1998; Teuchert‐Noodt et al ., 2000; Busche et al ., 2002).…”

Long-term effects of a single adult methamphetamine challenge: Minor impact on dopamine fibre density in limbic brain areas of gerbils

“…Some evidence exists that monoaminergic fibres are able to recover to some extend from this damage during long time course [ 5 - 9 ]. Moreover, even reactive overshoot was found for serotonergic fibres in several limbic areas of the brain, including left entorhinal cortex [ 10 ] and the septal pole of the hippocampal dentate gyrus [ 11 ]. For DA fibres, an early MA treatment produces hyperinnervation in amygdaloid nuclei and ventral entorhinal cortex [ 12 ] and a restraint of the maturation in prefrontal cortex [ 13 , 14 ].…”