Neuropeptides and psychiatry - basic and clinical aspects

HPA-related CSF neuropeptides in suicide attempters

Corticotropin-releasing hormone (CRH), somatostatin (SOM), delta-sleep-inducing peptide (DSIP), neuropeptide Y (NPY), beta-endorphin (beta-END), and vasopressin (AVP), which are regarded as being involved in the HPA-regulation were investigated in lumbar CSF of 44 suicide attempters. The patients were diagnosed according to the DSM-III-R, and rated with the MADRS. The neuropeptides were compared with the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in CSF and with post-dexamethasone plasma cortisol. We found strong correlations between CRH and the peptides SOM and beta-END. The latter also correlated positively with SOM. There were no differences between men and women. Patients with major depressive disorders had significantly lower SOM, CRH, and DSIP than other patients. Both SOM and beta-END correlated negatively with post dexamethasone plasma cortisol in all patients. We found no significant relationships between neuropeptides and CSF 5-HIAA. Patients who had made previous suicide attempts had significantly lower CRH than those who had not. No other significant associations between neuropeptides and suicidal subgroups of patients appeared, and there was no indication of specific neuropeptide patterns in patients who later completed suicide. Intercorrelations of some neuropeptides and low SOM and DSIP in major depressed patients are findings in line with those by others.

Preclinical and clinical studies with somatostatin related to the central nervous system

1. The tetradecapeptide somatostatin (SS) has a widespread, uneven distribution within several organs including the central nervous system (CNS), with particularly high concentration in the hypothalamus. 2. The SS-related peptides (SS28, SS28(1-12), SS28(15-28)) are originated from the precursor pre-prosomatostatin. 3. SS is suggested to be involved in a large number of CNS functions, locomotion, sedation, excitation, catatonia, body temperature, feeding, nociception, paradoxical sleep, self-stimulation, seizure, learning and memory. 4. SS influences central neurochemical processes. 5. It is possible that SS is related to various neurological and psychiatric illnesses, like Huntington's disease, multiple sclerosis, Parkinson's disease, epilepsy, eating disorders, Alzheimer's disease, schizophrenia and major depressive illness.

Neuropeptide Y (NPY) and the central nervous system: distribution effects and possible relationship to neurological and psychiatric disorders

1. NPY is a 36 amino acid tyrosine-rich peptide. It is one of the most abundant and widely distributed neuropeptides known today within the central nervous system with particularly high concentrations in the hypothalamus and in several limbic regions. 2. NPY seems to coexist with other on neurotransmitters like somatostatin, galanin, GABA and the catecholamines noradrenaline and adrenaline in discrete brain regions. 3. NPY binding sites are widely distributed in the brain. However they do not always overlap with the distribution of NPY-like immunoreactivity. 4. NPY is suggested to be involved in a large number of neuroendocrine functions, stress responses, circadian rhythms, central autonomic functions, eating and drinking behaviour, and sexual and motor behaviour. 5. Psychotropic drugs and neurotoxins can alter the NPY concentrations in discrete brain regions. 6. It is possible that NPY is related to various neurological and psychiatric illnesses, like Huntington's chorea, Alzheimer's disease, Parkinson's disease, eating disorders, and major depressive illness.