Hubungan densitas reseptor D1 dengan tampilan memori kerja :: Kajian Neurohistokimiawi keterlibatan sistem dopaminergik cortex prefrontalis tikus (Rattus norvegicus) setelah paparan stres kronk

PASIAK, Taufiq Fredrik, Prof.dr. Soedjono Aswin, Ph.D

2004 | Tesis | S2 Ilmu Kedokteran Dasar dan Biomedis

Latar belakang. Respon sistem saraf pusat terhadap stres merupakan adaptasi kritis organisme terhadap lingkungan yang penuh stres. Stres kronik dapat merusak fungsi kognisi, terutama memori. Memori kerja, yakni salah satu memori jangka pendek yang bertanggung jawab untuk pemanggilan kembali informasi dengan segera setelah diperoleh, dapat rusak oleh karena stres kronik. Kerusakan memori kerja ini berkaitan dengan system dopaminergik di Cortex prefrontalis (CPF), yakni kadar dopamin dan densitas reseptor D1. Tujuan. Penelitian ini bertujuan untuk mengungkapkan: 1) pengaruh stress kronik terhadap memori kerja, dan 2) hubungan antara densitas reseptor D1 dengan memori kerja. Metode. Tikus dibagi secara acak menjadi 2 kelompok (masing-masing terdiri dari 5 ekor), yakni kelompok kontrol (K) dan kelompok perlakuan (P). Selanjutnya,masing-masing kelompok dilatih di maze radial 8 lengan. Setelah dilatih, kelompok K dan P diuji kinerjanya di maze (selama 12 hari). Dimulai pada hari ke 13, kelompok P diberikan perlakuan berupa stres bising (100-105 dB, 8 jam perhari, selama 25 hari). Tampilan memori kerja kemudian diuji lagi untuk kelompok K dan P setelah perlakuan (12 hari). Selanjutnya, semua tikus dibunuh dengan perfusi transkardial dan daerah CPF diambil. Jaringan itu selanjutnya diberi perlakuan imunohistokimia. Hasil. Penelitian ini menunjukkan bahwa stres kronik menyebabkan penurunan tampilan memori kerja yang dikaitkan dengan mekanisme down regulation reseptor D1 di CPF. Secara statistik, korelasi antara memori kerja dengan densitas reseptor adalah 49 persen. Ini menunjukkan bahwa stres kronik menurunkan memori kerja melalui reseptor D1 yang dimediasi oleh hipodopaminergik di CPF. Perubahan aktivitas sistem dopaminergik di CPF yang diinduksi oleh stres kronik dipandang sebagai respon stres saja daripada disfungsi organik. Penurunan transmisi dopamin berlangsung secara serentak dengan penurunan kadar reseptor D1 melalui mekanisme down regulation. Kesimpulan. Dari penelitian ini dapat disimpulkan: 1) stres kronik dapat menurunkan memori kerja, dan 2) terdapat korelasi antara memori kerja dan densitas reseptor D1.

Introduction. The response of the CNS to stress is often critical to the adaptation of an organism to a stressful environment. Chronic stress can impairs the cognition function, especially memory. It can impairs the maintenance of a novel short term memory, i.e. working memory, which is the term applied to the aspect of memory responsible for the recall of information immediately after it has been presented. The impairment working memory relate with dopaminergic system in Prefrontal Cortex (PFC),i.e. level of dopamin and its receptor D1 density. Objective. The aim of this research was to investigate: 1) the effect of chronic stress on working memory, and 2) relation between receptor D1 density and working memory. Methods. The rats were divided randomly into two groups (each group consisted of five rats), i.e. control group (C) and treatment group (T). Then, each group was trained in eight radial arm maze. After trained, C and T group was tested in radial arm maze (12 days). Start in the 13rd day, the T group was treated with noise stress (100-105 db, 8 h/d, 25 days). Performance of working memory after treated was tested in maze for two groups (12 days). Next, all rats were killed by transcardial perfusion and the PFC regions were dissected. The tissues were treated with imunohistochemistry procedure. Result. The results indicate that chronic stress induces decrease of working memory performance related to down regulation of D1 receptor in PFC. Statistically, correlation between working memory with D1 receptor density (grade 1st ) is 49 percent. It showed that chronic stress induced impairment of working memory via D1 receptor mediated hypodopaminergic mechanism in PFC. The change of dopaminergic system activity in the PFC induced by chronic stress is thought to express as a stress respon than an organic dysfunction. Reduction of dopamin transmission concomitant with a decrease in level of D1 receptor via down regulation mechanism. Conclusion. The conclusion of this research showed that: 1) chronic stress can decrease working memory, and 2) there is correlation between working memory with D1 receptor density.

Kata Kunci : Stress Kronik,Memori Kerja,Densitas Reseptor D1, Chronic stress-working memory-dopaminergic system-receptor D1-Prefrontal Cortex